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the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .

if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode .

what would a diode look like on a circuit board ?

the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .

so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this .

what is the direction of current in a circuit ( outside of a dc battery ) ?

the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .

and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin .

electron flow vs proton flow ?

the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .

and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here .

why do n't the graphs beyond the moment that there stops being zero current ?

the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .

if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode .

ie what should the graph look like for higher voltages ?

the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .

is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is .

does the current just go to infinity because there is no resistance or something ?

the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .

is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is .

then how does holes constitute hole current ?

the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .

so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire .

how can be voltage in negative ?

the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .

the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes .

why does a photodiode require biasing ?

the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .

a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current .

is a transistor a diode and if it is could someone help me understand what exactly it does like how does it work ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body .

isnt the posterior pituitary the one that releases oxytosin and adh ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self .

what does the synthroid do ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone .

what is the role of oxytocin in male ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin .

what types of hormones does the pituitary gland produce ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea .

is the doctor feeling for my thyroid gland ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid .

and if so , why would getting a cold cause my thyroid to swell if its primary function is controlling metabolism ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea .

why is the thyroid gland larger and more protrusive in males ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self .

which term refers to bulging eyeballs ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally .

if the hypothalamus secretes paracrine hormones , why is it included in the endocrine system ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body .

which hormone stimulates the production of thyroid hormone ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ?

how are there trillions of cells in our body ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center .

is n't oxytocin the hormone that deals with pleasure , or is that something else ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck .

is it bad if one side of the pituitary gland is larger than the other side ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body .

which hormone is produced by heart ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones .

does the heart and the kidney have any endocrine functions ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below .

so the hypothalamus is a gland , right ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs .

how the chakra 's work in relationship to the sympathetic and parasympathetic nervous systems ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi .

what are the functions of norepinephrine ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood .

what is the mechanism of hgh effect on growth of soft tissues ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones .

so the pancreas is part of both the endocrine and exocrine system ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect .

as it releases chemical messages and secretions through ducts ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones .

what is the difference between endocrine and exocrine system ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine .

if the thyroid gland secrets only t3 and t4 hormones then where is calcitonin or thyrocacitonin secreted ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body .

what type of hormone is secreted by the heart ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below .

why is hypothalamus not called 'mater gland ' instead of pituitary gland ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below .

`` pituitary gland actives in our early days '' is it true ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone .

what is the role of the oxytocin ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain .

can someone give me a rundown of the hypothalamus ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body .

how come the hormone does n't stop and go around the whole body ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone .

is n't the adrenal cortex also involved with sex hormones ( androgens and estrogens ) ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone .

can someone explain what is the role of these cortical sex hormones ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape .

so , the main purpose of hormons is signal function , right ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally .

also what is the benefit of using hormones ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function .

do we know a specific reason why evolution went this way ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland .

what is the function of pituetary gland ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below .

so in continuation of what others were saying , i understand that the hypothalamus synthesizes the chemicals such as adh and oxytocin , but does it do that for the anterior pituitary gland ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin .

also , why does the body need all these extra glands if the hypothalamus synthesizes all the hormones ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves .

why was n't the thymus included ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine .

what 's the different between t3 and t4 ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones .

does our organs such as heart , stomach , kidney , intestine and pancreas count as the organs of the endocrine system ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones .

in another word can i say any organs that produce hormones be one of the endocrine system organs ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system .

and what is itsfunction in the t cell ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below .

is the communication between the hypothalamus to the pituitary endocrine , not paracrine ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid .

what is a natural way that a person with hypothyroidism can replace thyroxine in the body , without to taking levothyroxine or an artificial form of the thyroid hormone ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally .

- 0 , are n't the hormones released by hypothalamus that direct the pituitary gland called neuroendocrine hormones ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation .

do n't males have a little bit of estrogen and females a little bit of testosterone ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body .

the interleukin hormone is an autocrine hormone that acts on a cell that produced it but am i right , assuming that it is excreted and that it affects other tcells of the same class ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center .

so is oxytocin present only in females ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone .

i thought the pituitary gland secreted adh and oxytocin ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body .

how does the cells know that a hormone is being radioed to them and get ready with their receptors ?

have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .

and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away .

is n't the hemocrine hormones that function at a distance and not the endocrine ?

in the last video i had this 2 by 3 matrix a right here , and we figured out all of the subspaces that are associated with this matrix . we figured out its null space , its column space , we figured out the null space and column space of its transpose , which you could also call the left null space , and the row space , or what 's essentially the space spanned by a 's rows . let 's write it all in one place , because i realize it got a little disjointed , and see if we can visualize what all of these look like , especially relative to each other . so let me copy and paste my original matrix . copy , and then let me scroll down here and paste it over here , and hit paste . let me see if i can find our key takeaways from the last video . so our column space right here , of a , was this thing right here . let me write this . this was our column space . it was the span of the r2 vector 2 , 4 . let me copy that . copy that and bring it down . hit paste . this was our column space . let me write that . this is the column space of a . it was equal to that right there . and now what other things do we know ? well , we know that the left null space was a span of 2 , 1 . let me write that . so our left null space , or the null space of our transpose , either way , it was equal to the span of the r2 vector 2 , 1 , just like that . and then what was our null space ? our null space we figured out in the last video . here it is . it 's the span of these two r3 vectors . let me copy and paste that . hit copy . let me go down here . let me paste it . so that was our null space right there . and then finally , what was our row space ? what was our row space or the column space of our transpose ? so the column space of our transpose was the span of this r3 vector right there , so it was this one right here . so let me copy and paste it . copy and scroll down , and we can paste it just like that . ok , let 's see if we can visualize this now , now that we have them all in one place . so first of all , if we imagine a transformation , x , that is equal to a times x , our transformation is going to be a mapping from what ? x would be a member of r3 , so r3 would be our domain . so it would be a mapping from r3 and then it would be a mapping to r2 because we have two rows here , right ? you multiply a 2-by-3 matrix times a 3-by-1 vector , and you 're going to get a 2-by-1 vector , so it 's going to be a mapping to r2 . so that 's our codomain . so let 's draw our domains and our codomains . i 'll just write them very generally right here . so you could imagine r3 is our domain . and then our codomain is going to be r2 just like that . and our t is a mapping , or you could even imagine a is a mapping between any vector there and any vector there when you multiply them . now , what is our column space of a ? our column space of a is the span of the vector 2 minus 4 . it 's an r2 vector . this is a subspace of r2 . we could write this . so let me write this . so our column space of a , these are just all of the vectors that are spanned by this . we figured out that these guys are just multiples of this first guy , or we could have done it the other way . we could have said this guy and that guy are multiples of that guy , either way . but the basis is just one of these vectors . we just have to have one of these vectors , and so it was equal to this right here . so the column space is a subset of r2 . and what else is a subset of r2 ? well , our left null space . our left null space is also a subset of r2 . so let 's graph them , actually . so i wo n't be too exact , but you can imagine . let 's see , if we draw the vector 2 , 4 -- let me draw some axes here . let me scroll down a little bit . so if you have some vector -- let me draw my -- do this as neatly as possible . that 's my vertical axis . that is my horizontal axis . and then , what does the span of our column space look like ? so you draw the vector 2 , minus 4 , so you 're going to go out one , two , and then you 're going to go down one , two , three , four . so that 's what that vector looks like . and the span of this vector is essentially all of the multiples of this vector , where you could say linear combinations of it , but you 're taking a combination of just one vector , so it 's just going to be all of the multiples of this vector . so if i were to graph it , it would just be a line that is specified by all of the linear combinations of that vector right there . this right here is a graphical representation of the column space of a . now , let 's look at the left null space of a , or you could imagine , the null space of the transpose . they are the same thing . you saw why in the last video . what does this look like ? so the left null space is a span of 2 , 1 . so if you graph 2 , and then you go up 1 , it 's the graph of 2 , 1 , and it looks like this . let me do it in a different color . so that 's what the vector looks like . the vector looks like that , but of course , we want the span of that vector , so it 's going to be all of the combinations . all you can do when you combine one vector is just multiply it by a bunch of scalars , so it 's going to be all of the scalar multiples of that vector . so let me draw it like that . it 's going to be like that . and the first thing you might notice , let me write this . this is our left null space of a or the null space of our transpose . this is equal to the left null space of a . and actually , since we 're writing , we wrote this in terms of a transpose . it 's the null space of a transpose , which is the left null space of a . let 's write the column space of a also in terms of a transpose . this is equal to the row space of a transpose , right ? if you 're looking at the columns of a , everything it spans , the columns of a are the same things as the rows of a transpose . but the first thing that you see , when i just at least visually drew it like this , is that these two spaces look to be orthogonal to each other . it looks like i drew it in r2 . it looks like there 's a 90-degree angle there . and if we wanted to verify it , all we have to do is take the dot product . well , any vector that is in our column space , you could take an arbitrary vector that 's in our column space , it 's going to be equal to c times 2 minus 4 . so let me write that down . i want this stuff up here . i 'll scroll down a little bit . let 's say v1 is a member of our column space . and that means that v1 is going to be equal to some scalar multiple times the spanning vector of our column space , so some scale or multiple of this . so we could say it 's equal to c1 times 2 minus 4 . that 's some member of our column space . now , if we want some member of our left null space -- let 's write it here . so let 's say that v2 is some member of our left null space , or the null space of the transpose , then what does that mean ? that means v2 is going to be equal to some scalar multiple of the spanning vector of our left null space of 2 , 1 . so any vector that 's in our column space could be represented this way . any vector in our left null space can be represented this way . now , what happens if you take the dot product of these two characters ? so let me do it down here . i want to save some space for what we 're going to do in r3 , but let me take the dot product of these two characters . so v1 dot v2 is equal to -- i 'll arbitrarily switch colors -- c1 times 2 minus 4 dot c2 times 2 , 1 . and then the scalars , we 've seen this before . you can just say that this is the same thing as c1 , c2 times the dot product of 2 minus 4 dot 2 , 1 . and then what is this equal to ? this is going to be equal to c1 , c2 times 2 times 2 is 4 plus minus 4 times 1 : minus 4 . well , this is going to be equal to 0 , so this whole expression is going to be equal to 0 . and this was for any two vectors that are members of our column space and our left null space . they 're orthogonal to each other . so every member of our column space is going to be orthogonal to every member of our left null space , or every member of the null space of our transpose , and that was the case in this example . it actually turns out this is always going to be the case , that your column space of a matrix , its orthogonal complement is the left null space , or the null space of its transpose . i 'll prove that probably in the next video , either in the next video or the video after that , but you can see it visually for this example . now let 's draw the other two characters that we 're dealing with here . so we have our null space , which is the span of these two vectors in r3 . it 's a little bit more difficult to draw it , these two vectors in r3 right there . but what is the span of two vectors in r3 ? all of the linear combinations of two vectors in r3 is going to be a plane in r3 . so i 'll draw it in just very general terms right here . if we draw it in just very general terms , let me see . so it 's a plane in r3 that looks like that . maybe i 'll fill in the plane a little bit , give you some sense of what it looks like . this is the null space of a . it 's spanned by these two vectors . now , you could imagine these two vectors look something like -- i 'm drawing it very general , but if you take any linear combinations of these two guys , you 're going to get any vector that 's along this plane that goes in infinite directions . and , of course , the origin will be in these . all of these are valid subspaces . now , what does the row space of a look like ? or you could say the column space of a transpose ? well , it 's the span of this vector in r3 , but let 's see something interesting about this vector in r3 . how does it relate to these two vectors ? well , you may not see it immediately , although if you look at it closely , it might pop out at you , that this guy is orthogonal to both of these guys . notice , if you take the dot product of 2 minus 1 minus 3 , and you dotted it with 1/2 , 1 , 0 , what are you going to get ? you 're going to get 2 times 1/2 , which is 1 , plus minus 1 times 1 , which is minus 1 , plus minus 3 times 0 , which is 0 . so that 's when i dotted that guy with that guy right there . and then , when i take the dot of this guy with that guy , what do you get ? you get 3/2 , 0 and 1 , dotted with -- let me scroll down a little bit . i do n't want to write too small -- dotted with 1 , dotted with 2 minus 1 minus 3 . in the row space of a , i wrote the spanning vector there this time . i probably should n't have switched the order . but here , i 'm dotting it with this guy , and then here , i 'm dotting it with this guy right there . so if you take it , 3/2 times 2 is equal to 3 plus 0 times minus 1 is 0 , plus 1 times minus 3 is minus 3 , so it 's equal to 0 . so the fact that this guy is orthogonal to both of these spanning vectors , it also means that it 's orthogonal to any linear combination of those guys . maybe it might be useful for you to see that . so let 's take some member of our null space . so let 's say the vector v3 is a member of our null space . that means it 's a linear combination of that guy and that guy . those are the two spanning vectors . i 'd written it up here . these are our two spanning vectors . i need the space down here , so let me scroll down a little bit . these are the two spanning vectors . so that means that v3 can be written as some linear combination of these two guys that i squared off in pink . so let me just write it as maybe a times 3/2 , 0 , 1 plus b times 1/2 , 1 , 0 . now , what happens if i take the dot product of v3 and i dot it with any member of my row space right here ? so any member of my row space is going to be a multiple of this guy right here . that is the spanning vector of my row space . just let me actually create that . so let me say that v4 is a member of my row space , which is the column space of the transpose of a . and that means that v4 is equal to , let 's say , some scaling vector . i always use c a lot . let me use d. let 's say it 's d times my spanning vector . d times 2 minus 1 , 3 . so what is v3 , which is just any member of my null space dotted with v4 , which is any member of my row space ? so what is this going to be equal to ? this is going to be equal to this guy . so let me write it like this . a times 3/2 , 0 , 1 plus v times 1/2 , 1 , 0 dotted with this guy , dot d times 2 minus 1 , 3 . now , what is this going to be equal to ? well , we know all of the properties of vector dot products . we can distribute it and then take the scalars out . so this is going to be equal to -- i 'll skip a few steps here , but it 's going to be equal to -- ad times the dot product of 3/2 , 0 , 1 , dot 2 minus 1 , 3 -- just distribute it out to here -- plus bd times the dot product of 1/2 , 1 , 0 , dotted with 2 minus 1 , 3 . this is the dot product . i just distributed this term along these two terms right here . and we already know what these dot products are equal to . we did it right here . this dot product right here is that dot product . i just switched the order , so this is equal to 0 . and this dot product is that dot product , so this is also equal to 0 . so you take any member of your row space and you dot it with any member of your null space , and you 're going to get 0 , or any member of your row space is orthogonal to any member of your null space . and i did all of that to help our visualization . so we just saw that any member of our row space , which is the span of this vector , is orthogonal to any member of or null space . so my row space , which is just going to be a line in r3 because it 's just a multiple of a vector . it 's going to look like this . it 's going to be a line , and then it 's going to maybe go behind it . you ca n't see it there . it 's going to look like that , but it 's going to be orthogonal . so let me draw it . so this pink line right here in r3 , that is our row space of a , which is equal to the column space of a transpose because the rows of a are the same thing as the columns of a transposed , and the row space is just the space spanned by your row vectors . and then this is the null space of a , which is a plane . it 's spanned by two vectors in r3 . or we could also call that the left null space of a transpose . and i never used this term in the last video , but it 's symmetric , right ? if the null space of a transpose is the left null space of a , then the null space of a is the left null space of a transpose , which is an interesting takeaway . notice that you have here the row space of a is orthogonal to the null space of a . and here , you have the row space of a transpose is orthogonal to the null space of a transpose . or you could say the left null space of a is orthogonal to the column space of a . or you could say the left null space of a transpose is orthogonal to the column space of a transpose . so these are just very interesting takeaways , in general . and just like i said here , that look , these happen to be orthogonal . these also happen to be orthogonal . and this is n't just some strange coincidence . in the next video or two , i 'll show you that this space , this pink space , is the orthogonal complement of the null space right here , which means it represents all of the vectors that are orthogonal to the null space . and these two guys are orthogonal complements to each other . they each represent all of the vectors that are orthogonal to the other guy in their respective spaces .

so let me write it like this . a times 3/2 , 0 , 1 plus v times 1/2 , 1 , 0 dotted with this guy , dot d times 2 minus 1 , 3 . now , what is this going to be equal to ?

what is nullspace , rowspace , and collumnspace ?

in the last video i had this 2 by 3 matrix a right here , and we figured out all of the subspaces that are associated with this matrix . we figured out its null space , its column space , we figured out the null space and column space of its transpose , which you could also call the left null space , and the row space , or what 's essentially the space spanned by a 's rows . let 's write it all in one place , because i realize it got a little disjointed , and see if we can visualize what all of these look like , especially relative to each other . so let me copy and paste my original matrix . copy , and then let me scroll down here and paste it over here , and hit paste . let me see if i can find our key takeaways from the last video . so our column space right here , of a , was this thing right here . let me write this . this was our column space . it was the span of the r2 vector 2 , 4 . let me copy that . copy that and bring it down . hit paste . this was our column space . let me write that . this is the column space of a . it was equal to that right there . and now what other things do we know ? well , we know that the left null space was a span of 2 , 1 . let me write that . so our left null space , or the null space of our transpose , either way , it was equal to the span of the r2 vector 2 , 1 , just like that . and then what was our null space ? our null space we figured out in the last video . here it is . it 's the span of these two r3 vectors . let me copy and paste that . hit copy . let me go down here . let me paste it . so that was our null space right there . and then finally , what was our row space ? what was our row space or the column space of our transpose ? so the column space of our transpose was the span of this r3 vector right there , so it was this one right here . so let me copy and paste it . copy and scroll down , and we can paste it just like that . ok , let 's see if we can visualize this now , now that we have them all in one place . so first of all , if we imagine a transformation , x , that is equal to a times x , our transformation is going to be a mapping from what ? x would be a member of r3 , so r3 would be our domain . so it would be a mapping from r3 and then it would be a mapping to r2 because we have two rows here , right ? you multiply a 2-by-3 matrix times a 3-by-1 vector , and you 're going to get a 2-by-1 vector , so it 's going to be a mapping to r2 . so that 's our codomain . so let 's draw our domains and our codomains . i 'll just write them very generally right here . so you could imagine r3 is our domain . and then our codomain is going to be r2 just like that . and our t is a mapping , or you could even imagine a is a mapping between any vector there and any vector there when you multiply them . now , what is our column space of a ? our column space of a is the span of the vector 2 minus 4 . it 's an r2 vector . this is a subspace of r2 . we could write this . so let me write this . so our column space of a , these are just all of the vectors that are spanned by this . we figured out that these guys are just multiples of this first guy , or we could have done it the other way . we could have said this guy and that guy are multiples of that guy , either way . but the basis is just one of these vectors . we just have to have one of these vectors , and so it was equal to this right here . so the column space is a subset of r2 . and what else is a subset of r2 ? well , our left null space . our left null space is also a subset of r2 . so let 's graph them , actually . so i wo n't be too exact , but you can imagine . let 's see , if we draw the vector 2 , 4 -- let me draw some axes here . let me scroll down a little bit . so if you have some vector -- let me draw my -- do this as neatly as possible . that 's my vertical axis . that is my horizontal axis . and then , what does the span of our column space look like ? so you draw the vector 2 , minus 4 , so you 're going to go out one , two , and then you 're going to go down one , two , three , four . so that 's what that vector looks like . and the span of this vector is essentially all of the multiples of this vector , where you could say linear combinations of it , but you 're taking a combination of just one vector , so it 's just going to be all of the multiples of this vector . so if i were to graph it , it would just be a line that is specified by all of the linear combinations of that vector right there . this right here is a graphical representation of the column space of a . now , let 's look at the left null space of a , or you could imagine , the null space of the transpose . they are the same thing . you saw why in the last video . what does this look like ? so the left null space is a span of 2 , 1 . so if you graph 2 , and then you go up 1 , it 's the graph of 2 , 1 , and it looks like this . let me do it in a different color . so that 's what the vector looks like . the vector looks like that , but of course , we want the span of that vector , so it 's going to be all of the combinations . all you can do when you combine one vector is just multiply it by a bunch of scalars , so it 's going to be all of the scalar multiples of that vector . so let me draw it like that . it 's going to be like that . and the first thing you might notice , let me write this . this is our left null space of a or the null space of our transpose . this is equal to the left null space of a . and actually , since we 're writing , we wrote this in terms of a transpose . it 's the null space of a transpose , which is the left null space of a . let 's write the column space of a also in terms of a transpose . this is equal to the row space of a transpose , right ? if you 're looking at the columns of a , everything it spans , the columns of a are the same things as the rows of a transpose . but the first thing that you see , when i just at least visually drew it like this , is that these two spaces look to be orthogonal to each other . it looks like i drew it in r2 . it looks like there 's a 90-degree angle there . and if we wanted to verify it , all we have to do is take the dot product . well , any vector that is in our column space , you could take an arbitrary vector that 's in our column space , it 's going to be equal to c times 2 minus 4 . so let me write that down . i want this stuff up here . i 'll scroll down a little bit . let 's say v1 is a member of our column space . and that means that v1 is going to be equal to some scalar multiple times the spanning vector of our column space , so some scale or multiple of this . so we could say it 's equal to c1 times 2 minus 4 . that 's some member of our column space . now , if we want some member of our left null space -- let 's write it here . so let 's say that v2 is some member of our left null space , or the null space of the transpose , then what does that mean ? that means v2 is going to be equal to some scalar multiple of the spanning vector of our left null space of 2 , 1 . so any vector that 's in our column space could be represented this way . any vector in our left null space can be represented this way . now , what happens if you take the dot product of these two characters ? so let me do it down here . i want to save some space for what we 're going to do in r3 , but let me take the dot product of these two characters . so v1 dot v2 is equal to -- i 'll arbitrarily switch colors -- c1 times 2 minus 4 dot c2 times 2 , 1 . and then the scalars , we 've seen this before . you can just say that this is the same thing as c1 , c2 times the dot product of 2 minus 4 dot 2 , 1 . and then what is this equal to ? this is going to be equal to c1 , c2 times 2 times 2 is 4 plus minus 4 times 1 : minus 4 . well , this is going to be equal to 0 , so this whole expression is going to be equal to 0 . and this was for any two vectors that are members of our column space and our left null space . they 're orthogonal to each other . so every member of our column space is going to be orthogonal to every member of our left null space , or every member of the null space of our transpose , and that was the case in this example . it actually turns out this is always going to be the case , that your column space of a matrix , its orthogonal complement is the left null space , or the null space of its transpose . i 'll prove that probably in the next video , either in the next video or the video after that , but you can see it visually for this example . now let 's draw the other two characters that we 're dealing with here . so we have our null space , which is the span of these two vectors in r3 . it 's a little bit more difficult to draw it , these two vectors in r3 right there . but what is the span of two vectors in r3 ? all of the linear combinations of two vectors in r3 is going to be a plane in r3 . so i 'll draw it in just very general terms right here . if we draw it in just very general terms , let me see . so it 's a plane in r3 that looks like that . maybe i 'll fill in the plane a little bit , give you some sense of what it looks like . this is the null space of a . it 's spanned by these two vectors . now , you could imagine these two vectors look something like -- i 'm drawing it very general , but if you take any linear combinations of these two guys , you 're going to get any vector that 's along this plane that goes in infinite directions . and , of course , the origin will be in these . all of these are valid subspaces . now , what does the row space of a look like ? or you could say the column space of a transpose ? well , it 's the span of this vector in r3 , but let 's see something interesting about this vector in r3 . how does it relate to these two vectors ? well , you may not see it immediately , although if you look at it closely , it might pop out at you , that this guy is orthogonal to both of these guys . notice , if you take the dot product of 2 minus 1 minus 3 , and you dotted it with 1/2 , 1 , 0 , what are you going to get ? you 're going to get 2 times 1/2 , which is 1 , plus minus 1 times 1 , which is minus 1 , plus minus 3 times 0 , which is 0 . so that 's when i dotted that guy with that guy right there . and then , when i take the dot of this guy with that guy , what do you get ? you get 3/2 , 0 and 1 , dotted with -- let me scroll down a little bit . i do n't want to write too small -- dotted with 1 , dotted with 2 minus 1 minus 3 . in the row space of a , i wrote the spanning vector there this time . i probably should n't have switched the order . but here , i 'm dotting it with this guy , and then here , i 'm dotting it with this guy right there . so if you take it , 3/2 times 2 is equal to 3 plus 0 times minus 1 is 0 , plus 1 times minus 3 is minus 3 , so it 's equal to 0 . so the fact that this guy is orthogonal to both of these spanning vectors , it also means that it 's orthogonal to any linear combination of those guys . maybe it might be useful for you to see that . so let 's take some member of our null space . so let 's say the vector v3 is a member of our null space . that means it 's a linear combination of that guy and that guy . those are the two spanning vectors . i 'd written it up here . these are our two spanning vectors . i need the space down here , so let me scroll down a little bit . these are the two spanning vectors . so that means that v3 can be written as some linear combination of these two guys that i squared off in pink . so let me just write it as maybe a times 3/2 , 0 , 1 plus b times 1/2 , 1 , 0 . now , what happens if i take the dot product of v3 and i dot it with any member of my row space right here ? so any member of my row space is going to be a multiple of this guy right here . that is the spanning vector of my row space . just let me actually create that . so let me say that v4 is a member of my row space , which is the column space of the transpose of a . and that means that v4 is equal to , let 's say , some scaling vector . i always use c a lot . let me use d. let 's say it 's d times my spanning vector . d times 2 minus 1 , 3 . so what is v3 , which is just any member of my null space dotted with v4 , which is any member of my row space ? so what is this going to be equal to ? this is going to be equal to this guy . so let me write it like this . a times 3/2 , 0 , 1 plus v times 1/2 , 1 , 0 dotted with this guy , dot d times 2 minus 1 , 3 . now , what is this going to be equal to ? well , we know all of the properties of vector dot products . we can distribute it and then take the scalars out . so this is going to be equal to -- i 'll skip a few steps here , but it 's going to be equal to -- ad times the dot product of 3/2 , 0 , 1 , dot 2 minus 1 , 3 -- just distribute it out to here -- plus bd times the dot product of 1/2 , 1 , 0 , dotted with 2 minus 1 , 3 . this is the dot product . i just distributed this term along these two terms right here . and we already know what these dot products are equal to . we did it right here . this dot product right here is that dot product . i just switched the order , so this is equal to 0 . and this dot product is that dot product , so this is also equal to 0 . so you take any member of your row space and you dot it with any member of your null space , and you 're going to get 0 , or any member of your row space is orthogonal to any member of your null space . and i did all of that to help our visualization . so we just saw that any member of our row space , which is the span of this vector , is orthogonal to any member of or null space . so my row space , which is just going to be a line in r3 because it 's just a multiple of a vector . it 's going to look like this . it 's going to be a line , and then it 's going to maybe go behind it . you ca n't see it there . it 's going to look like that , but it 's going to be orthogonal . so let me draw it . so this pink line right here in r3 , that is our row space of a , which is equal to the column space of a transpose because the rows of a are the same thing as the columns of a transposed , and the row space is just the space spanned by your row vectors . and then this is the null space of a , which is a plane . it 's spanned by two vectors in r3 . or we could also call that the left null space of a transpose . and i never used this term in the last video , but it 's symmetric , right ? if the null space of a transpose is the left null space of a , then the null space of a is the left null space of a transpose , which is an interesting takeaway . notice that you have here the row space of a is orthogonal to the null space of a . and here , you have the row space of a transpose is orthogonal to the null space of a transpose . or you could say the left null space of a is orthogonal to the column space of a . or you could say the left null space of a transpose is orthogonal to the column space of a transpose . so these are just very interesting takeaways , in general . and just like i said here , that look , these happen to be orthogonal . these also happen to be orthogonal . and this is n't just some strange coincidence . in the next video or two , i 'll show you that this space , this pink space , is the orthogonal complement of the null space right here , which means it represents all of the vectors that are orthogonal to the null space . and these two guys are orthogonal complements to each other . they each represent all of the vectors that are orthogonal to the other guy in their respective spaces .

and what else is a subset of r2 ? well , our left null space . our left null space is also a subset of r2 .

but why does left null space belong to the codomain ?

in the last video i had this 2 by 3 matrix a right here , and we figured out all of the subspaces that are associated with this matrix . we figured out its null space , its column space , we figured out the null space and column space of its transpose , which you could also call the left null space , and the row space , or what 's essentially the space spanned by a 's rows . let 's write it all in one place , because i realize it got a little disjointed , and see if we can visualize what all of these look like , especially relative to each other . so let me copy and paste my original matrix . copy , and then let me scroll down here and paste it over here , and hit paste . let me see if i can find our key takeaways from the last video . so our column space right here , of a , was this thing right here . let me write this . this was our column space . it was the span of the r2 vector 2 , 4 . let me copy that . copy that and bring it down . hit paste . this was our column space . let me write that . this is the column space of a . it was equal to that right there . and now what other things do we know ? well , we know that the left null space was a span of 2 , 1 . let me write that . so our left null space , or the null space of our transpose , either way , it was equal to the span of the r2 vector 2 , 1 , just like that . and then what was our null space ? our null space we figured out in the last video . here it is . it 's the span of these two r3 vectors . let me copy and paste that . hit copy . let me go down here . let me paste it . so that was our null space right there . and then finally , what was our row space ? what was our row space or the column space of our transpose ? so the column space of our transpose was the span of this r3 vector right there , so it was this one right here . so let me copy and paste it . copy and scroll down , and we can paste it just like that . ok , let 's see if we can visualize this now , now that we have them all in one place . so first of all , if we imagine a transformation , x , that is equal to a times x , our transformation is going to be a mapping from what ? x would be a member of r3 , so r3 would be our domain . so it would be a mapping from r3 and then it would be a mapping to r2 because we have two rows here , right ? you multiply a 2-by-3 matrix times a 3-by-1 vector , and you 're going to get a 2-by-1 vector , so it 's going to be a mapping to r2 . so that 's our codomain . so let 's draw our domains and our codomains . i 'll just write them very generally right here . so you could imagine r3 is our domain . and then our codomain is going to be r2 just like that . and our t is a mapping , or you could even imagine a is a mapping between any vector there and any vector there when you multiply them . now , what is our column space of a ? our column space of a is the span of the vector 2 minus 4 . it 's an r2 vector . this is a subspace of r2 . we could write this . so let me write this . so our column space of a , these are just all of the vectors that are spanned by this . we figured out that these guys are just multiples of this first guy , or we could have done it the other way . we could have said this guy and that guy are multiples of that guy , either way . but the basis is just one of these vectors . we just have to have one of these vectors , and so it was equal to this right here . so the column space is a subset of r2 . and what else is a subset of r2 ? well , our left null space . our left null space is also a subset of r2 . so let 's graph them , actually . so i wo n't be too exact , but you can imagine . let 's see , if we draw the vector 2 , 4 -- let me draw some axes here . let me scroll down a little bit . so if you have some vector -- let me draw my -- do this as neatly as possible . that 's my vertical axis . that is my horizontal axis . and then , what does the span of our column space look like ? so you draw the vector 2 , minus 4 , so you 're going to go out one , two , and then you 're going to go down one , two , three , four . so that 's what that vector looks like . and the span of this vector is essentially all of the multiples of this vector , where you could say linear combinations of it , but you 're taking a combination of just one vector , so it 's just going to be all of the multiples of this vector . so if i were to graph it , it would just be a line that is specified by all of the linear combinations of that vector right there . this right here is a graphical representation of the column space of a . now , let 's look at the left null space of a , or you could imagine , the null space of the transpose . they are the same thing . you saw why in the last video . what does this look like ? so the left null space is a span of 2 , 1 . so if you graph 2 , and then you go up 1 , it 's the graph of 2 , 1 , and it looks like this . let me do it in a different color . so that 's what the vector looks like . the vector looks like that , but of course , we want the span of that vector , so it 's going to be all of the combinations . all you can do when you combine one vector is just multiply it by a bunch of scalars , so it 's going to be all of the scalar multiples of that vector . so let me draw it like that . it 's going to be like that . and the first thing you might notice , let me write this . this is our left null space of a or the null space of our transpose . this is equal to the left null space of a . and actually , since we 're writing , we wrote this in terms of a transpose . it 's the null space of a transpose , which is the left null space of a . let 's write the column space of a also in terms of a transpose . this is equal to the row space of a transpose , right ? if you 're looking at the columns of a , everything it spans , the columns of a are the same things as the rows of a transpose . but the first thing that you see , when i just at least visually drew it like this , is that these two spaces look to be orthogonal to each other . it looks like i drew it in r2 . it looks like there 's a 90-degree angle there . and if we wanted to verify it , all we have to do is take the dot product . well , any vector that is in our column space , you could take an arbitrary vector that 's in our column space , it 's going to be equal to c times 2 minus 4 . so let me write that down . i want this stuff up here . i 'll scroll down a little bit . let 's say v1 is a member of our column space . and that means that v1 is going to be equal to some scalar multiple times the spanning vector of our column space , so some scale or multiple of this . so we could say it 's equal to c1 times 2 minus 4 . that 's some member of our column space . now , if we want some member of our left null space -- let 's write it here . so let 's say that v2 is some member of our left null space , or the null space of the transpose , then what does that mean ? that means v2 is going to be equal to some scalar multiple of the spanning vector of our left null space of 2 , 1 . so any vector that 's in our column space could be represented this way . any vector in our left null space can be represented this way . now , what happens if you take the dot product of these two characters ? so let me do it down here . i want to save some space for what we 're going to do in r3 , but let me take the dot product of these two characters . so v1 dot v2 is equal to -- i 'll arbitrarily switch colors -- c1 times 2 minus 4 dot c2 times 2 , 1 . and then the scalars , we 've seen this before . you can just say that this is the same thing as c1 , c2 times the dot product of 2 minus 4 dot 2 , 1 . and then what is this equal to ? this is going to be equal to c1 , c2 times 2 times 2 is 4 plus minus 4 times 1 : minus 4 . well , this is going to be equal to 0 , so this whole expression is going to be equal to 0 . and this was for any two vectors that are members of our column space and our left null space . they 're orthogonal to each other . so every member of our column space is going to be orthogonal to every member of our left null space , or every member of the null space of our transpose , and that was the case in this example . it actually turns out this is always going to be the case , that your column space of a matrix , its orthogonal complement is the left null space , or the null space of its transpose . i 'll prove that probably in the next video , either in the next video or the video after that , but you can see it visually for this example . now let 's draw the other two characters that we 're dealing with here . so we have our null space , which is the span of these two vectors in r3 . it 's a little bit more difficult to draw it , these two vectors in r3 right there . but what is the span of two vectors in r3 ? all of the linear combinations of two vectors in r3 is going to be a plane in r3 . so i 'll draw it in just very general terms right here . if we draw it in just very general terms , let me see . so it 's a plane in r3 that looks like that . maybe i 'll fill in the plane a little bit , give you some sense of what it looks like . this is the null space of a . it 's spanned by these two vectors . now , you could imagine these two vectors look something like -- i 'm drawing it very general , but if you take any linear combinations of these two guys , you 're going to get any vector that 's along this plane that goes in infinite directions . and , of course , the origin will be in these . all of these are valid subspaces . now , what does the row space of a look like ? or you could say the column space of a transpose ? well , it 's the span of this vector in r3 , but let 's see something interesting about this vector in r3 . how does it relate to these two vectors ? well , you may not see it immediately , although if you look at it closely , it might pop out at you , that this guy is orthogonal to both of these guys . notice , if you take the dot product of 2 minus 1 minus 3 , and you dotted it with 1/2 , 1 , 0 , what are you going to get ? you 're going to get 2 times 1/2 , which is 1 , plus minus 1 times 1 , which is minus 1 , plus minus 3 times 0 , which is 0 . so that 's when i dotted that guy with that guy right there . and then , when i take the dot of this guy with that guy , what do you get ? you get 3/2 , 0 and 1 , dotted with -- let me scroll down a little bit . i do n't want to write too small -- dotted with 1 , dotted with 2 minus 1 minus 3 . in the row space of a , i wrote the spanning vector there this time . i probably should n't have switched the order . but here , i 'm dotting it with this guy , and then here , i 'm dotting it with this guy right there . so if you take it , 3/2 times 2 is equal to 3 plus 0 times minus 1 is 0 , plus 1 times minus 3 is minus 3 , so it 's equal to 0 . so the fact that this guy is orthogonal to both of these spanning vectors , it also means that it 's orthogonal to any linear combination of those guys . maybe it might be useful for you to see that . so let 's take some member of our null space . so let 's say the vector v3 is a member of our null space . that means it 's a linear combination of that guy and that guy . those are the two spanning vectors . i 'd written it up here . these are our two spanning vectors . i need the space down here , so let me scroll down a little bit . these are the two spanning vectors . so that means that v3 can be written as some linear combination of these two guys that i squared off in pink . so let me just write it as maybe a times 3/2 , 0 , 1 plus b times 1/2 , 1 , 0 . now , what happens if i take the dot product of v3 and i dot it with any member of my row space right here ? so any member of my row space is going to be a multiple of this guy right here . that is the spanning vector of my row space . just let me actually create that . so let me say that v4 is a member of my row space , which is the column space of the transpose of a . and that means that v4 is equal to , let 's say , some scaling vector . i always use c a lot . let me use d. let 's say it 's d times my spanning vector . d times 2 minus 1 , 3 . so what is v3 , which is just any member of my null space dotted with v4 , which is any member of my row space ? so what is this going to be equal to ? this is going to be equal to this guy . so let me write it like this . a times 3/2 , 0 , 1 plus v times 1/2 , 1 , 0 dotted with this guy , dot d times 2 minus 1 , 3 . now , what is this going to be equal to ? well , we know all of the properties of vector dot products . we can distribute it and then take the scalars out . so this is going to be equal to -- i 'll skip a few steps here , but it 's going to be equal to -- ad times the dot product of 3/2 , 0 , 1 , dot 2 minus 1 , 3 -- just distribute it out to here -- plus bd times the dot product of 1/2 , 1 , 0 , dotted with 2 minus 1 , 3 . this is the dot product . i just distributed this term along these two terms right here . and we already know what these dot products are equal to . we did it right here . this dot product right here is that dot product . i just switched the order , so this is equal to 0 . and this dot product is that dot product , so this is also equal to 0 . so you take any member of your row space and you dot it with any member of your null space , and you 're going to get 0 , or any member of your row space is orthogonal to any member of your null space . and i did all of that to help our visualization . so we just saw that any member of our row space , which is the span of this vector , is orthogonal to any member of or null space . so my row space , which is just going to be a line in r3 because it 's just a multiple of a vector . it 's going to look like this . it 's going to be a line , and then it 's going to maybe go behind it . you ca n't see it there . it 's going to look like that , but it 's going to be orthogonal . so let me draw it . so this pink line right here in r3 , that is our row space of a , which is equal to the column space of a transpose because the rows of a are the same thing as the columns of a transposed , and the row space is just the space spanned by your row vectors . and then this is the null space of a , which is a plane . it 's spanned by two vectors in r3 . or we could also call that the left null space of a transpose . and i never used this term in the last video , but it 's symmetric , right ? if the null space of a transpose is the left null space of a , then the null space of a is the left null space of a transpose , which is an interesting takeaway . notice that you have here the row space of a is orthogonal to the null space of a . and here , you have the row space of a transpose is orthogonal to the null space of a transpose . or you could say the left null space of a is orthogonal to the column space of a . or you could say the left null space of a transpose is orthogonal to the column space of a transpose . so these are just very interesting takeaways , in general . and just like i said here , that look , these happen to be orthogonal . these also happen to be orthogonal . and this is n't just some strange coincidence . in the next video or two , i 'll show you that this space , this pink space , is the orthogonal complement of the null space right here , which means it represents all of the vectors that are orthogonal to the null space . and these two guys are orthogonal complements to each other . they each represent all of the vectors that are orthogonal to the other guy in their respective spaces .

and that means that v4 is equal to , let 's say , some scaling vector . i always use c a lot . let me use d. let 's say it 's d times my spanning vector .

is that correct that the cross product of the span of n ( a ) is always part of c ( at ) ?

in the last video i had this 2 by 3 matrix a right here , and we figured out all of the subspaces that are associated with this matrix . we figured out its null space , its column space , we figured out the null space and column space of its transpose , which you could also call the left null space , and the row space , or what 's essentially the space spanned by a 's rows . let 's write it all in one place , because i realize it got a little disjointed , and see if we can visualize what all of these look like , especially relative to each other . so let me copy and paste my original matrix . copy , and then let me scroll down here and paste it over here , and hit paste . let me see if i can find our key takeaways from the last video . so our column space right here , of a , was this thing right here . let me write this . this was our column space . it was the span of the r2 vector 2 , 4 . let me copy that . copy that and bring it down . hit paste . this was our column space . let me write that . this is the column space of a . it was equal to that right there . and now what other things do we know ? well , we know that the left null space was a span of 2 , 1 . let me write that . so our left null space , or the null space of our transpose , either way , it was equal to the span of the r2 vector 2 , 1 , just like that . and then what was our null space ? our null space we figured out in the last video . here it is . it 's the span of these two r3 vectors . let me copy and paste that . hit copy . let me go down here . let me paste it . so that was our null space right there . and then finally , what was our row space ? what was our row space or the column space of our transpose ? so the column space of our transpose was the span of this r3 vector right there , so it was this one right here . so let me copy and paste it . copy and scroll down , and we can paste it just like that . ok , let 's see if we can visualize this now , now that we have them all in one place . so first of all , if we imagine a transformation , x , that is equal to a times x , our transformation is going to be a mapping from what ? x would be a member of r3 , so r3 would be our domain . so it would be a mapping from r3 and then it would be a mapping to r2 because we have two rows here , right ? you multiply a 2-by-3 matrix times a 3-by-1 vector , and you 're going to get a 2-by-1 vector , so it 's going to be a mapping to r2 . so that 's our codomain . so let 's draw our domains and our codomains . i 'll just write them very generally right here . so you could imagine r3 is our domain . and then our codomain is going to be r2 just like that . and our t is a mapping , or you could even imagine a is a mapping between any vector there and any vector there when you multiply them . now , what is our column space of a ? our column space of a is the span of the vector 2 minus 4 . it 's an r2 vector . this is a subspace of r2 . we could write this . so let me write this . so our column space of a , these are just all of the vectors that are spanned by this . we figured out that these guys are just multiples of this first guy , or we could have done it the other way . we could have said this guy and that guy are multiples of that guy , either way . but the basis is just one of these vectors . we just have to have one of these vectors , and so it was equal to this right here . so the column space is a subset of r2 . and what else is a subset of r2 ? well , our left null space . our left null space is also a subset of r2 . so let 's graph them , actually . so i wo n't be too exact , but you can imagine . let 's see , if we draw the vector 2 , 4 -- let me draw some axes here . let me scroll down a little bit . so if you have some vector -- let me draw my -- do this as neatly as possible . that 's my vertical axis . that is my horizontal axis . and then , what does the span of our column space look like ? so you draw the vector 2 , minus 4 , so you 're going to go out one , two , and then you 're going to go down one , two , three , four . so that 's what that vector looks like . and the span of this vector is essentially all of the multiples of this vector , where you could say linear combinations of it , but you 're taking a combination of just one vector , so it 's just going to be all of the multiples of this vector . so if i were to graph it , it would just be a line that is specified by all of the linear combinations of that vector right there . this right here is a graphical representation of the column space of a . now , let 's look at the left null space of a , or you could imagine , the null space of the transpose . they are the same thing . you saw why in the last video . what does this look like ? so the left null space is a span of 2 , 1 . so if you graph 2 , and then you go up 1 , it 's the graph of 2 , 1 , and it looks like this . let me do it in a different color . so that 's what the vector looks like . the vector looks like that , but of course , we want the span of that vector , so it 's going to be all of the combinations . all you can do when you combine one vector is just multiply it by a bunch of scalars , so it 's going to be all of the scalar multiples of that vector . so let me draw it like that . it 's going to be like that . and the first thing you might notice , let me write this . this is our left null space of a or the null space of our transpose . this is equal to the left null space of a . and actually , since we 're writing , we wrote this in terms of a transpose . it 's the null space of a transpose , which is the left null space of a . let 's write the column space of a also in terms of a transpose . this is equal to the row space of a transpose , right ? if you 're looking at the columns of a , everything it spans , the columns of a are the same things as the rows of a transpose . but the first thing that you see , when i just at least visually drew it like this , is that these two spaces look to be orthogonal to each other . it looks like i drew it in r2 . it looks like there 's a 90-degree angle there . and if we wanted to verify it , all we have to do is take the dot product . well , any vector that is in our column space , you could take an arbitrary vector that 's in our column space , it 's going to be equal to c times 2 minus 4 . so let me write that down . i want this stuff up here . i 'll scroll down a little bit . let 's say v1 is a member of our column space . and that means that v1 is going to be equal to some scalar multiple times the spanning vector of our column space , so some scale or multiple of this . so we could say it 's equal to c1 times 2 minus 4 . that 's some member of our column space . now , if we want some member of our left null space -- let 's write it here . so let 's say that v2 is some member of our left null space , or the null space of the transpose , then what does that mean ? that means v2 is going to be equal to some scalar multiple of the spanning vector of our left null space of 2 , 1 . so any vector that 's in our column space could be represented this way . any vector in our left null space can be represented this way . now , what happens if you take the dot product of these two characters ? so let me do it down here . i want to save some space for what we 're going to do in r3 , but let me take the dot product of these two characters . so v1 dot v2 is equal to -- i 'll arbitrarily switch colors -- c1 times 2 minus 4 dot c2 times 2 , 1 . and then the scalars , we 've seen this before . you can just say that this is the same thing as c1 , c2 times the dot product of 2 minus 4 dot 2 , 1 . and then what is this equal to ? this is going to be equal to c1 , c2 times 2 times 2 is 4 plus minus 4 times 1 : minus 4 . well , this is going to be equal to 0 , so this whole expression is going to be equal to 0 . and this was for any two vectors that are members of our column space and our left null space . they 're orthogonal to each other . so every member of our column space is going to be orthogonal to every member of our left null space , or every member of the null space of our transpose , and that was the case in this example . it actually turns out this is always going to be the case , that your column space of a matrix , its orthogonal complement is the left null space , or the null space of its transpose . i 'll prove that probably in the next video , either in the next video or the video after that , but you can see it visually for this example . now let 's draw the other two characters that we 're dealing with here . so we have our null space , which is the span of these two vectors in r3 . it 's a little bit more difficult to draw it , these two vectors in r3 right there . but what is the span of two vectors in r3 ? all of the linear combinations of two vectors in r3 is going to be a plane in r3 . so i 'll draw it in just very general terms right here . if we draw it in just very general terms , let me see . so it 's a plane in r3 that looks like that . maybe i 'll fill in the plane a little bit , give you some sense of what it looks like . this is the null space of a . it 's spanned by these two vectors . now , you could imagine these two vectors look something like -- i 'm drawing it very general , but if you take any linear combinations of these two guys , you 're going to get any vector that 's along this plane that goes in infinite directions . and , of course , the origin will be in these . all of these are valid subspaces . now , what does the row space of a look like ? or you could say the column space of a transpose ? well , it 's the span of this vector in r3 , but let 's see something interesting about this vector in r3 . how does it relate to these two vectors ? well , you may not see it immediately , although if you look at it closely , it might pop out at you , that this guy is orthogonal to both of these guys . notice , if you take the dot product of 2 minus 1 minus 3 , and you dotted it with 1/2 , 1 , 0 , what are you going to get ? you 're going to get 2 times 1/2 , which is 1 , plus minus 1 times 1 , which is minus 1 , plus minus 3 times 0 , which is 0 . so that 's when i dotted that guy with that guy right there . and then , when i take the dot of this guy with that guy , what do you get ? you get 3/2 , 0 and 1 , dotted with -- let me scroll down a little bit . i do n't want to write too small -- dotted with 1 , dotted with 2 minus 1 minus 3 . in the row space of a , i wrote the spanning vector there this time . i probably should n't have switched the order . but here , i 'm dotting it with this guy , and then here , i 'm dotting it with this guy right there . so if you take it , 3/2 times 2 is equal to 3 plus 0 times minus 1 is 0 , plus 1 times minus 3 is minus 3 , so it 's equal to 0 . so the fact that this guy is orthogonal to both of these spanning vectors , it also means that it 's orthogonal to any linear combination of those guys . maybe it might be useful for you to see that . so let 's take some member of our null space . so let 's say the vector v3 is a member of our null space . that means it 's a linear combination of that guy and that guy . those are the two spanning vectors . i 'd written it up here . these are our two spanning vectors . i need the space down here , so let me scroll down a little bit . these are the two spanning vectors . so that means that v3 can be written as some linear combination of these two guys that i squared off in pink . so let me just write it as maybe a times 3/2 , 0 , 1 plus b times 1/2 , 1 , 0 . now , what happens if i take the dot product of v3 and i dot it with any member of my row space right here ? so any member of my row space is going to be a multiple of this guy right here . that is the spanning vector of my row space . just let me actually create that . so let me say that v4 is a member of my row space , which is the column space of the transpose of a . and that means that v4 is equal to , let 's say , some scaling vector . i always use c a lot . let me use d. let 's say it 's d times my spanning vector . d times 2 minus 1 , 3 . so what is v3 , which is just any member of my null space dotted with v4 , which is any member of my row space ? so what is this going to be equal to ? this is going to be equal to this guy . so let me write it like this . a times 3/2 , 0 , 1 plus v times 1/2 , 1 , 0 dotted with this guy , dot d times 2 minus 1 , 3 . now , what is this going to be equal to ? well , we know all of the properties of vector dot products . we can distribute it and then take the scalars out . so this is going to be equal to -- i 'll skip a few steps here , but it 's going to be equal to -- ad times the dot product of 3/2 , 0 , 1 , dot 2 minus 1 , 3 -- just distribute it out to here -- plus bd times the dot product of 1/2 , 1 , 0 , dotted with 2 minus 1 , 3 . this is the dot product . i just distributed this term along these two terms right here . and we already know what these dot products are equal to . we did it right here . this dot product right here is that dot product . i just switched the order , so this is equal to 0 . and this dot product is that dot product , so this is also equal to 0 . so you take any member of your row space and you dot it with any member of your null space , and you 're going to get 0 , or any member of your row space is orthogonal to any member of your null space . and i did all of that to help our visualization . so we just saw that any member of our row space , which is the span of this vector , is orthogonal to any member of or null space . so my row space , which is just going to be a line in r3 because it 's just a multiple of a vector . it 's going to look like this . it 's going to be a line , and then it 's going to maybe go behind it . you ca n't see it there . it 's going to look like that , but it 's going to be orthogonal . so let me draw it . so this pink line right here in r3 , that is our row space of a , which is equal to the column space of a transpose because the rows of a are the same thing as the columns of a transposed , and the row space is just the space spanned by your row vectors . and then this is the null space of a , which is a plane . it 's spanned by two vectors in r3 . or we could also call that the left null space of a transpose . and i never used this term in the last video , but it 's symmetric , right ? if the null space of a transpose is the left null space of a , then the null space of a is the left null space of a transpose , which is an interesting takeaway . notice that you have here the row space of a is orthogonal to the null space of a . and here , you have the row space of a transpose is orthogonal to the null space of a transpose . or you could say the left null space of a is orthogonal to the column space of a . or you could say the left null space of a transpose is orthogonal to the column space of a transpose . so these are just very interesting takeaways , in general . and just like i said here , that look , these happen to be orthogonal . these also happen to be orthogonal . and this is n't just some strange coincidence . in the next video or two , i 'll show you that this space , this pink space , is the orthogonal complement of the null space right here , which means it represents all of the vectors that are orthogonal to the null space . and these two guys are orthogonal complements to each other . they each represent all of the vectors that are orthogonal to the other guy in their respective spaces .

our column space of a is the span of the vector 2 minus 4 . it 's an r2 vector . this is a subspace of r2 .

do i understand correctly that the ( 0 ) t vector = 0 vector ?

the starting block below is 2 units long . use the tools to the right to convert the starting block into both of the goal blocks , that are 5/8 units long , and 1 and 3/4 units long . you can see your progress as the current block . so what are they telling us to do ? so this is the starting block , right over here . they 're telling us this is 2 units long . so a unit must be about this long , right here . about half of this starting block . and we have these tools on the right . and my first goal block , right over here in blue , they say that that 's 5/8 . and that makes sense , because if this is about a whole , then that looks like about 5/8 . this right over here would be about 8/8 . so this looks about 5/8 . and then they tell us that this other one that 's below my screen right over here is 1 and 3/4 . so they tell us that this is 1 and 3/4 units long . 1 and 3/4 is also the same thing as 7/4 . so i somehow need to -- let 's see , what are my tools ? what are the tools available to me ? well i can cut my starting block into a certain number of pieces . and then i 'm going to copy that starting block over here for block 1 , and i 'm going to try to match it to this goal block . and then i 'm also going to copy it for block 2 , to match that second goal block . so i 'm going to try to get something that 's 5/8 , and i 'm also going to try to get something that 's 1 and 3/4 . now 3/4 is the same thing as 6/8 . and the reason why i care about eighths is eighths is a smaller unit . so if i can convert the starting block into eighths , then i can copy it enough times to get exactly to 5/8 , and exactly to 1 and 3/4 , which is the same thing as -- 3/4 is the exact same thing as 6/8 . so let 's get our starting block into eighths . so if we 're starting with 2 wholes , if we 're starting with 2 units long -- so if i cut it once , now this is a whole unit . now if i cut a whole , now if i cut it twice , so now if i cut 4 times , so i 've cut my original block into 4 times . so now this right over here is half a unit . and actually , if i want to convert it into eighths i need to cut it 16 times . so let me do that . 15 , 16 . so i cut 2 units into 16 equal pieces . or i guess this is 1/16 of 2 , so that is going to be an eighth . and now i just have to multiply this the appropriate number of times . this right over here is 5/8 . this is 1/8 . so let me copy this , 1 , 2 , 3 , 4 , 5 . so that is 5/8 . and then here , i need to do 1 and 3/4 . remember , 1 and 3/4 is the same thing as 7/4 . it 's 4/4 plus 3/4 , which is 7/4 . 7/4 is the same thing as 14/8 . so this right over here is 1/8 , i just need to make 14 of these . 2 , 3 , 4 , 5 , 6 , 7 , 8 . actually , let me show you what i 'm doing . 9 , 10 , 11 , 12 , 13 , 14 . and there we go . that 's exactly the same length as goal block 2 . this is 14/8 . 14/8 is the exact same length as this . 14/8 is the same thing as 7/4 , which is the same thing as 1 and 3/4 . this is 5/8 , which is the same thing as 5/8 . so let 's check our answer . and we got it right .

so this right over here is 1/8 , i just need to make 14 of these . 2 , 3 , 4 , 5 , 6 , 7 , 8 . actually , let me show you what i 'm doing .

if you have 5/8 and 1 6/8 , why do you have to cut the starting block into 16 ?

the starting block below is 2 units long . use the tools to the right to convert the starting block into both of the goal blocks , that are 5/8 units long , and 1 and 3/4 units long . you can see your progress as the current block . so what are they telling us to do ? so this is the starting block , right over here . they 're telling us this is 2 units long . so a unit must be about this long , right here . about half of this starting block . and we have these tools on the right . and my first goal block , right over here in blue , they say that that 's 5/8 . and that makes sense , because if this is about a whole , then that looks like about 5/8 . this right over here would be about 8/8 . so this looks about 5/8 . and then they tell us that this other one that 's below my screen right over here is 1 and 3/4 . so they tell us that this is 1 and 3/4 units long . 1 and 3/4 is also the same thing as 7/4 . so i somehow need to -- let 's see , what are my tools ? what are the tools available to me ? well i can cut my starting block into a certain number of pieces . and then i 'm going to copy that starting block over here for block 1 , and i 'm going to try to match it to this goal block . and then i 'm also going to copy it for block 2 , to match that second goal block . so i 'm going to try to get something that 's 5/8 , and i 'm also going to try to get something that 's 1 and 3/4 . now 3/4 is the same thing as 6/8 . and the reason why i care about eighths is eighths is a smaller unit . so if i can convert the starting block into eighths , then i can copy it enough times to get exactly to 5/8 , and exactly to 1 and 3/4 , which is the same thing as -- 3/4 is the exact same thing as 6/8 . so let 's get our starting block into eighths . so if we 're starting with 2 wholes , if we 're starting with 2 units long -- so if i cut it once , now this is a whole unit . now if i cut a whole , now if i cut it twice , so now if i cut 4 times , so i 've cut my original block into 4 times . so now this right over here is half a unit . and actually , if i want to convert it into eighths i need to cut it 16 times . so let me do that . 15 , 16 . so i cut 2 units into 16 equal pieces . or i guess this is 1/16 of 2 , so that is going to be an eighth . and now i just have to multiply this the appropriate number of times . this right over here is 5/8 . this is 1/8 . so let me copy this , 1 , 2 , 3 , 4 , 5 . so that is 5/8 . and then here , i need to do 1 and 3/4 . remember , 1 and 3/4 is the same thing as 7/4 . it 's 4/4 plus 3/4 , which is 7/4 . 7/4 is the same thing as 14/8 . so this right over here is 1/8 , i just need to make 14 of these . 2 , 3 , 4 , 5 , 6 , 7 , 8 . actually , let me show you what i 'm doing . 9 , 10 , 11 , 12 , 13 , 14 . and there we go . that 's exactly the same length as goal block 2 . this is 14/8 . 14/8 is the exact same length as this . 14/8 is the same thing as 7/4 , which is the same thing as 1 and 3/4 . this is 5/8 , which is the same thing as 5/8 . so let 's check our answer . and we got it right .

and that makes sense , because if this is about a whole , then that looks like about 5/8 . this right over here would be about 8/8 . so this looks about 5/8 .

if a/b is an improper fraction when divided by 6/25 or 8/15 when would the quotient be a whole number ?

the starting block below is 2 units long . use the tools to the right to convert the starting block into both of the goal blocks , that are 5/8 units long , and 1 and 3/4 units long . you can see your progress as the current block . so what are they telling us to do ? so this is the starting block , right over here . they 're telling us this is 2 units long . so a unit must be about this long , right here . about half of this starting block . and we have these tools on the right . and my first goal block , right over here in blue , they say that that 's 5/8 . and that makes sense , because if this is about a whole , then that looks like about 5/8 . this right over here would be about 8/8 . so this looks about 5/8 . and then they tell us that this other one that 's below my screen right over here is 1 and 3/4 . so they tell us that this is 1 and 3/4 units long . 1 and 3/4 is also the same thing as 7/4 . so i somehow need to -- let 's see , what are my tools ? what are the tools available to me ? well i can cut my starting block into a certain number of pieces . and then i 'm going to copy that starting block over here for block 1 , and i 'm going to try to match it to this goal block . and then i 'm also going to copy it for block 2 , to match that second goal block . so i 'm going to try to get something that 's 5/8 , and i 'm also going to try to get something that 's 1 and 3/4 . now 3/4 is the same thing as 6/8 . and the reason why i care about eighths is eighths is a smaller unit . so if i can convert the starting block into eighths , then i can copy it enough times to get exactly to 5/8 , and exactly to 1 and 3/4 , which is the same thing as -- 3/4 is the exact same thing as 6/8 . so let 's get our starting block into eighths . so if we 're starting with 2 wholes , if we 're starting with 2 units long -- so if i cut it once , now this is a whole unit . now if i cut a whole , now if i cut it twice , so now if i cut 4 times , so i 've cut my original block into 4 times . so now this right over here is half a unit . and actually , if i want to convert it into eighths i need to cut it 16 times . so let me do that . 15 , 16 . so i cut 2 units into 16 equal pieces . or i guess this is 1/16 of 2 , so that is going to be an eighth . and now i just have to multiply this the appropriate number of times . this right over here is 5/8 . this is 1/8 . so let me copy this , 1 , 2 , 3 , 4 , 5 . so that is 5/8 . and then here , i need to do 1 and 3/4 . remember , 1 and 3/4 is the same thing as 7/4 . it 's 4/4 plus 3/4 , which is 7/4 . 7/4 is the same thing as 14/8 . so this right over here is 1/8 , i just need to make 14 of these . 2 , 3 , 4 , 5 , 6 , 7 , 8 . actually , let me show you what i 'm doing . 9 , 10 , 11 , 12 , 13 , 14 . and there we go . that 's exactly the same length as goal block 2 . this is 14/8 . 14/8 is the exact same length as this . 14/8 is the same thing as 7/4 , which is the same thing as 1 and 3/4 . this is 5/8 , which is the same thing as 5/8 . so let 's check our answer . and we got it right .

and that makes sense , because if this is about a whole , then that looks like about 5/8 . this right over here would be about 8/8 . so this looks about 5/8 .

what would be the use of this knowledge in day to day life ?

the starting block below is 2 units long . use the tools to the right to convert the starting block into both of the goal blocks , that are 5/8 units long , and 1 and 3/4 units long . you can see your progress as the current block . so what are they telling us to do ? so this is the starting block , right over here . they 're telling us this is 2 units long . so a unit must be about this long , right here . about half of this starting block . and we have these tools on the right . and my first goal block , right over here in blue , they say that that 's 5/8 . and that makes sense , because if this is about a whole , then that looks like about 5/8 . this right over here would be about 8/8 . so this looks about 5/8 . and then they tell us that this other one that 's below my screen right over here is 1 and 3/4 . so they tell us that this is 1 and 3/4 units long . 1 and 3/4 is also the same thing as 7/4 . so i somehow need to -- let 's see , what are my tools ? what are the tools available to me ? well i can cut my starting block into a certain number of pieces . and then i 'm going to copy that starting block over here for block 1 , and i 'm going to try to match it to this goal block . and then i 'm also going to copy it for block 2 , to match that second goal block . so i 'm going to try to get something that 's 5/8 , and i 'm also going to try to get something that 's 1 and 3/4 . now 3/4 is the same thing as 6/8 . and the reason why i care about eighths is eighths is a smaller unit . so if i can convert the starting block into eighths , then i can copy it enough times to get exactly to 5/8 , and exactly to 1 and 3/4 , which is the same thing as -- 3/4 is the exact same thing as 6/8 . so let 's get our starting block into eighths . so if we 're starting with 2 wholes , if we 're starting with 2 units long -- so if i cut it once , now this is a whole unit . now if i cut a whole , now if i cut it twice , so now if i cut 4 times , so i 've cut my original block into 4 times . so now this right over here is half a unit . and actually , if i want to convert it into eighths i need to cut it 16 times . so let me do that . 15 , 16 . so i cut 2 units into 16 equal pieces . or i guess this is 1/16 of 2 , so that is going to be an eighth . and now i just have to multiply this the appropriate number of times . this right over here is 5/8 . this is 1/8 . so let me copy this , 1 , 2 , 3 , 4 , 5 . so that is 5/8 . and then here , i need to do 1 and 3/4 . remember , 1 and 3/4 is the same thing as 7/4 . it 's 4/4 plus 3/4 , which is 7/4 . 7/4 is the same thing as 14/8 . so this right over here is 1/8 , i just need to make 14 of these . 2 , 3 , 4 , 5 , 6 , 7 , 8 . actually , let me show you what i 'm doing . 9 , 10 , 11 , 12 , 13 , 14 . and there we go . that 's exactly the same length as goal block 2 . this is 14/8 . 14/8 is the exact same length as this . 14/8 is the same thing as 7/4 , which is the same thing as 1 and 3/4 . this is 5/8 , which is the same thing as 5/8 . so let 's check our answer . and we got it right .

this right over here is 5/8 . this is 1/8 . so let me copy this , 1 , 2 , 3 , 4 , 5 . so that is 5/8 .

to test some people : 1/2 + 1/3 + 1/4 + 1/5 ... 1/9 + 1/10 ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets .

so what the hedge funds bought really is n't insurance , is it ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating .

you have to have an `` insurable interest '' in order to buy insurance , right ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy .

why are these side bets allowed ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on .

when the ratings agencies are suggested to be sloppy , is n't it also a possibility that they knew that the writer had a less than perfect credit rating ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for .

but instead of paying out $ 4 or $ 5 billion to its cds counter parties would it not make sense for aig to just shell out that $ 1 billion to the company which is going to default essentially prevent the credit default ; so it does not have to pay out for all the cds obligations ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default .

7 instead of betting for whether a corp will fail or not , can these third parties bet for whether a corp will succeed in paying its debt or not & if corp succeed in paying debt they get money on that ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy .

who came up with that side bet idea , and when did it started to happen ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges .

does n't legislation needs to be created for such things to happen ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet .

what benefits does the side bets bring to the economy that would justify those laws being passed ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here .

did the aig 's and other cds writers take out re-insurance on their obligations ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default .

however is it permissible for a hedge fund who already purchased cds 's on a company to also take a short position or buy put options ( on the very same company ) which will also benefit the hedge fund from the company 's defaulting ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy .

is there really no rules or laws at all to regulate all these side bets ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated .

does a bank selling its mortgages to an investment bank required by its regulator to risk rate the mortgages for the purchaser ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default .

when a company that has sold debt defaults , why is only the principal considered for insurance under the cds setup ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail .

would n't it make sense for cds buyers to setup the cds so that in case of a default , the cds seller owes them not only the principal on the bond , but also the coupon payments accrued ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps .

how are cds specifically associated with mortgages ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail .

how is credit default swap accounted for in the balance sheet ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets .

how does one dump a debt onto the market ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest .

when these corporations default , do the investors still have legal rights to chase and recover the debt ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest .

so in a perfect scenario , investors would get back their full capital ( from writers ) and potentially a little more ( from their debt recovery efforts ) ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous .

did they know credit default swaps are unregulated ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy .

when more side bets were made , did the premium on the side bets increase , due to an increase demand ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets .

should n't normal market pressures make side bets less enticing over time , and prevent excessive risk taking ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest .

investors could ask insurance corporation to give insurance premiums against a company and insurance corporation would surely give them insurance without taking into account the ratings of those companies ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here .

in other words , can aig write the cds and sell it to an investor that wants to take on the risk of paying the notional amount , with the potential upside of just collecting the premium amounts every quarter ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble .

in addition , what is the impact of entering into a cds on the financial statement to either the party ( the pension fund or hedge fund or the cds issuer ) ?

let 's think a little bit about why credit default swaps , or famously referred to by warren buffett as financial weapons of mass destruction . at the center of it -- and there 's not just one credit default swap writer , but i 'll put one in the middle because each of them are writing many , many credit default swaps . aig is the most famous . but you have some writer here . they 're given some good credit rating . maybe in the past that credit rating was actually earned by a credit rating agency . and then frankly , the credit rating agency got a little sloppy and really was n't willing to downgrade them given all of the credit default swaps , all of the obligations they are taking on . and as you could tell , i kind of view these guys and these guys as the main culprits , and maybe a little bit of the regulatory agencies saying , hey , look , these guys are writing insurance . maybe we should actually regulate them . but with that said , you have companies over here . i 'll do the companies in this pink color . and they want to borrow money from other parties , let 's say , investors . i 'll do the investors in this orange color . so the investors are lending them money . the companies give them interest . so investors lending money , giving interest , lending money , giving interest , lending money , giving interest . and then these investors -- it seems pretty reasonable -- say , hey , look , there 's a guy over here with a double a rating . the people that we 're lending to do n't have a double a rating . maybe this guy has a b , maybe this guy has a double b , maybe this guy only has a single a . and so he says , look , i want to be completely safe here so i 'm going to pay a little bit of a premium to aig or to the writer , whoever the writer is , and in exchange i will get insurance on this debt . and it seems pretty reasonable except for the fact that this player right over here did not put out any money aside or did not put the appropriate amount of money aside to properly account for all of these liabilities , all of this risk that its taking on . and also , all of these risks are correlated . you can imagine a situation where the economy goes bad . now , all of a sudden this company defaults on its debt and this company defaults on its debt . in fact , when the economy 's good , it 's likely that very few of these companies are going to default and when the economy goes bad , it 's likely that many of them will default . but the real problem is is as soon as these defaults start happening , then the credit default swap writer is going to have to actually start paying for the defaults . they 'll get the bad debt and in exchange they 'll make the other side of the credit default swap , the holder of it , they will pay to make them whole . and so this could take them out of business . and all of a sudden , the people over here who thought that they had insurance no longer do . and they might actually say , wait , i can only hold double a debt and they might actually have to dump this debt on to the market . even worse , you have all of the people over here who did n't lend any money to anybody , but they really just wanted to make side bets . either the side bets might have been pure directional bets on the state of the economy saying , hey , i think a bunch of companies or i think this company in particular is going to default on its debt , and they too could get credit default swaps really as just side bets . so just for maybe this right here is $ 1 billion in debt , maybe all of these parties took side bets on this guy . so even though there 's only $ 1 billion of debt here , there might be $ 4 or $ 5 or $ 10 billion worth of insurance on that $ 1 billion bet . so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges . the only reason why they might have felt comfortable taking on some other liability is they said , look , if the economy goes really bad , i have this insurance over here . and they did that transaction with another third party . now all of a sudden , if the economy goes bad and these guys say , hey , look , i 'm in a lot of trouble . good thing i have this credit default swap , but then it turns out that they do n't because the counterparty here fails , the credit default swap writer , now all of a sudden this guy becomes insolvent . but this guy was dependent on this guy paying and he thought he was good because he even looked at this guy 's books and said this guy had offsetting hedges , and now this guy might fail . and so you could have this entire cascade through the entire financial system .

so if all of a sudden this one company ca n't pay its $ 1 billion , now aig is on the line not for $ 1 billion , but for $ 4 or $ 5 or $ 6 billion , however much it insured it for . so it allows people to insure for things that they do n't have the offsetting liability for . and so you can imagine , some of these people -- if this guy fails will just take a loss and that 's bad and all of the rest because they were expecting that they would n't -- but some of these players might have had offsetting hedges .

i know the so called premium will affect the profiit & loss statement , but the notional amount is not a liability , is it ?

in this video , we are going to give ourselves an overview of ancient egypt , which corresponds geographically pretty closely to the modern day state of egypt in northeast africa . now the central feature in both ancient egypt and in modern egypt is the nile river that you see in blue right over here . and the nile river is one of the great rivers of the world . it rivals the amazon river as the longest river and it sources the tributaries of the nile rover start even south of this picture and the water flows northward and eventually its delta reaches the mediterranean sea . the delta , which is where a river opens into the sea , is called a delta because , as you can see , these rivers , you can even see it from the satellite pictures right over here , they start branching up a bunch and you have this upside down triangular region , which looks a little bit like an upside down greek letter delta , so that 's why river delta is called that . and this one just happens to be upside down . if it was flowing the other way , it would be a right-side-up delta . so the nile river , it flows from , you could say , eastern mid-africa up into the mediterranean sea and because it has this northward flow , the southern parts of the river are upriver and they are actually called the upper nile . so , upper . the upper nile is actually south of the lower nile , of the lower nile . and once again , that 's because the upper nile is up river , it 's also flowing from higher elevations to lower elevations . so as you go south , you get to higher and higher elevations . now , the reason why the river is so important , we studied this multiple times , rivers are a source of fresh water , when they flood they make the surrounding soil fertile , they 're suitable for agriculture , and the nile valley is one of the first places that we see agriculture emerging during the neolithic period . in fact , human settlement we believe was along this nile river valley as far as 6,000 bce or 8,000 years ago , and it might have been there even further back in time . and because you have that agriculture , it allowed for higher population densities , which allowed for more specialization of labor and more complex societies . it 's not a coincidence that some of the first , that one of the first great civilizations emerged here . now , the story of the nile river , or of egypt , and actually they are tied very closely , even though egypt is considered a lot of this region , most of the human population , this is true even today , is right along the river , around that fertile soil , where the agriculture actually occurs . in fact , this was so important to the ancient egyptians that their whole calendar , their seasons , were based on what the nile river was doing . they had a season called the inundation , or the flooding of the river , which makes the soil fertile . they had a season of growth , which is now talking about the growth of the crops and they had a season of harvest . and so you had people in this valley for thousands of years , but when we talk about ancient egypt , we formally talk about it as a civilization around 3,100 , 3,150 bce . and this is where we get to our timeline right over here . so we 're talking about right around there on our timeline and the reason why this is considered the beginning of the ancient egyptian civilization is this is when we believe that upper and lower egypt were first united under the king and there 's different names used , narmer sometimes or menes . i 'm going to mispronounce things every now and then and i 'm probably doing it here as well . and so he was the king that unified upper and lower egypt into an empire and the empire , as we will see , which lasted thousands of years , every one of these spaces is a hundred years . we 're gon na go over huge time span , but the ancient egyptian civilization is roughly divided into three kingdoms . you have the old kingdom , which went from about , right from about the 27th century bce up to about the 17th century bce . you have the middle kingdom and you have the new kingdom . and once again , this is spanning right over here over a thousand years of history . and in between those , you have these intermediate periods where the kingdom or the empire was a little bit more fragmented . you have in some of these intermediate periods , you have some foreign rule . but just to get a sense of some of what happened over this thousands of years , and i 'm kind of laughing in my head because it 's hard to cover over two , 3,000 years , in the course of just a few minutes , but this will give you a sense of what ancient egyptian civilization was all about . now the kings are referred to as pharaohs but as we 'll see that term pharaoh is not really used until we get to the new kingdom . but i will refer to the kings as pharaohs throughout this video , just to say , hey these are the egyptian kings . and the old kingdom is probably most known today in our popular culture for what we most associate with ancient egypt and that is the pyramids . and here , right over here are the pyramids , there 's the great pyramid of giza , which is near modern-day cairo today . this is the sphinx and they were built in that old period under the pharaohs sneferu and khufu , right over here in the 26th century bce . and we are still trying to get a better understanding of how this was done . we actually now do n't believe that it was done by slave labor , but instead it was done during , you could say , the off season by the peasants as a form of taxation . okay , you 're done planting or harvesting your crops ? well now that you have some time , and this shows actually the importance of agriculture for freeing people up , so to speak , why do n't you help the pharaohs built these massive tombs , which i 've seen various estimates that it might have taken some place between 10 and 100,000 people several decades to build each . but these are even today , these were built over 4,500 years ago , are some of the most iconic symbols that humanity has ever created . and the reason why we know so much about ancient egypt is that we have been able to decipher their writing . it 's a symbolic , they have these pictographs , these hieroglyphics , i 'm sure you 've heard of the word before , and for a while we had no idea what they said . we would see these encryptions in these tombs and we had a sense that , okay these tombs , especially things like the pyramids would be for these great kings , we could tell that it was a stratified society , that nobility had better tombs than others , but we did n't really have a good sense of what was going on until we discovered this , which is the rosetta stone , which was discovered in 1799 . the reason why this is so valuable is it has the same text written in three different languages . it has it written in the hieroglyphs of the ancient egyptians , and it has it written in a later script used in egypt , called demotic egyptian , and most importantly , it has it also written in greek . and so historians were able to say , okay , we can now start to decipher what these symbols mean because we have a translation of them and that 's why it 's one of the first civilizations where we 're able to put the picture together . and hieroglyphics are one of the first forms of writing . but let 's now go on in our journey through thousands of years of ancient egyptian civilization . between the old kingdom and the middle kingdom , you have the first intermediate period and then you have the middle kingdom and then you have the hyksos , which are semitic people , semitic referring to their language being of the same family as semitic languages like arabic , or hebrew , or aramaic . but then you have the new kingdom , and the new kingdom is considered to be the peak of ancient egypt . it 's really the height of their technology , it 's the height of their military capability . and there are several pharaohs that are worthy of note in the new kingdom . the first is , he was born amenhotep or he was originally known as amenhotep the fourth and then he eventually names himself akhenaton and akhenaton means effective for aton , aton being a significant egyptian god . and the reason why he changed his name is he decides that , okay we have , the egyptians have this huge pantheon of gods . here is just the some of them right over here , this is the god osiris , often associated with the afterlife or transition , regeneration , resurrection . you have the god amun here and his first name amenhotep , it means amun is satisfied . what is considered kind of the equivalent of zeus , you have the god here horus , once again a very significant god at different times in egypt , but what was interesting about amenhotep the fourth or akhenaton , whichever name you want to use , is he decided , no , no , no , i do n't like this pantheon , this polytheistic religion that we have , i wan na worship one god , and the god that he decides to worship is really the , you could consider it the sun god , or the sun disc , and its representation looks something like this and it was referred to as aten and so he changes his name to akhenaton and he actually starts to try to get rid of evidence of these other gods or to make them a lot less important . and so the reason why that 's notable is this is viewed as perhaps one of the first attempts at monotheism , at least within this ancient egyptian civilization . he 's also noted for giving a lot of power to his wife , to the queen , nefertiti , who some people say was second in command , or even co-ruled alongside him . now he was also famous because after his death , eventually , his son , king tut , tutankhamen , comes to power . and the reason why king tut , as he 's often known , although it 's tutankhamen , is known is because we were able to find his tombs in relatively good order and so he 's become a popular part of the imagination . and he 's known as a child pharaoh . he comes to power when he 's very young , he dies at 18 and so it 's kind of an interesting story . now , most prominent amongst all of the pharaohs across egyptian history , and this is also in the new kingdom , comes a little bit after tutankhamen , is ramses the second . and ramses the second , who emerges here in the 13th century , and he rules for most of the 13th century bce , he represents really the peak of egypt , ancient egypt , as a military power . he 's famous for the battle at kaddish , which is the earliest battle where we actually know what the tactics and the formations were and it was with the also significant hittite empire in 1274 bce , this is an image drawn much , much later , of the battle of kaddish . the battle , we now believe , might have been a bit of a stalemate , ramses the second was n't able to capture kaddish , but has told us a lot about military tactics and strategy and formation of that time . historians today think it might have been the largest chariot battle maybe ever . so this was a significant thing that happened . now , eventually the new kingdom does collapse , as we get to the end of the second millennium , and then over the next several hundreds of years , we 're talking about a very long period of time , it gets fragmented , you have several rulers , you have the kushites rule from the upper nile , the kushites were in this area right over here . they rule for a brief period . the assyrians , that 's a mesopotamian civilization , they rule for a small period of time , and then eventually and we talk about this in some detail in other videos , you have the persians take over , you have cambyses , cyrus the great 's son , he 's able to rule over , he 's able to conquer egypt and egypt becomes part of the achaemenid empire for a while until the conquering of alexander the great . and after alexander the great dies , one of his generals and his dynasty takes over , ptolemaic egypt and now it 's being ruled by foreigners , well it 's been ruled by foreigners for a while now , but now it 's by the greeks and the famous cleopatra , who 's considered a pharaoh of egypt , she 's actually greek by blood , she 's actually the one that seduced you could say julius cesar and marc antony and after cleopatra 's death , more and more , actually eventually it becomes part of rome . so as you can see we covered this enormous large time period in history , one of the most significant civilizations in all of history , one of the most famous poems about civilizations and rulers , about ramses the second , the poem ozymandias was named after him . you have some of the great cities of the ancient world , thebes , which was the capital during parts of the new kingdom and the middle kingdom , you have memphis , which was one of the , some people say founded by menes and the capital of the old kingdom . these were all happening in ancient egypt .

but i will refer to the kings as pharaohs throughout this video , just to say , hey these are the egyptian kings . and the old kingdom is probably most known today in our popular culture for what we most associate with ancient egypt and that is the pyramids . and here , right over here are the pyramids , there 's the great pyramid of giza , which is near modern-day cairo today . this is the sphinx and they were built in that old period under the pharaohs sneferu and khufu , right over here in the 26th century bce .

what kind of traps were in pyramids ?

in this video , we are going to give ourselves an overview of ancient egypt , which corresponds geographically pretty closely to the modern day state of egypt in northeast africa . now the central feature in both ancient egypt and in modern egypt is the nile river that you see in blue right over here . and the nile river is one of the great rivers of the world . it rivals the amazon river as the longest river and it sources the tributaries of the nile rover start even south of this picture and the water flows northward and eventually its delta reaches the mediterranean sea . the delta , which is where a river opens into the sea , is called a delta because , as you can see , these rivers , you can even see it from the satellite pictures right over here , they start branching up a bunch and you have this upside down triangular region , which looks a little bit like an upside down greek letter delta , so that 's why river delta is called that . and this one just happens to be upside down . if it was flowing the other way , it would be a right-side-up delta . so the nile river , it flows from , you could say , eastern mid-africa up into the mediterranean sea and because it has this northward flow , the southern parts of the river are upriver and they are actually called the upper nile . so , upper . the upper nile is actually south of the lower nile , of the lower nile . and once again , that 's because the upper nile is up river , it 's also flowing from higher elevations to lower elevations . so as you go south , you get to higher and higher elevations . now , the reason why the river is so important , we studied this multiple times , rivers are a source of fresh water , when they flood they make the surrounding soil fertile , they 're suitable for agriculture , and the nile valley is one of the first places that we see agriculture emerging during the neolithic period . in fact , human settlement we believe was along this nile river valley as far as 6,000 bce or 8,000 years ago , and it might have been there even further back in time . and because you have that agriculture , it allowed for higher population densities , which allowed for more specialization of labor and more complex societies . it 's not a coincidence that some of the first , that one of the first great civilizations emerged here . now , the story of the nile river , or of egypt , and actually they are tied very closely , even though egypt is considered a lot of this region , most of the human population , this is true even today , is right along the river , around that fertile soil , where the agriculture actually occurs . in fact , this was so important to the ancient egyptians that their whole calendar , their seasons , were based on what the nile river was doing . they had a season called the inundation , or the flooding of the river , which makes the soil fertile . they had a season of growth , which is now talking about the growth of the crops and they had a season of harvest . and so you had people in this valley for thousands of years , but when we talk about ancient egypt , we formally talk about it as a civilization around 3,100 , 3,150 bce . and this is where we get to our timeline right over here . so we 're talking about right around there on our timeline and the reason why this is considered the beginning of the ancient egyptian civilization is this is when we believe that upper and lower egypt were first united under the king and there 's different names used , narmer sometimes or menes . i 'm going to mispronounce things every now and then and i 'm probably doing it here as well . and so he was the king that unified upper and lower egypt into an empire and the empire , as we will see , which lasted thousands of years , every one of these spaces is a hundred years . we 're gon na go over huge time span , but the ancient egyptian civilization is roughly divided into three kingdoms . you have the old kingdom , which went from about , right from about the 27th century bce up to about the 17th century bce . you have the middle kingdom and you have the new kingdom . and once again , this is spanning right over here over a thousand years of history . and in between those , you have these intermediate periods where the kingdom or the empire was a little bit more fragmented . you have in some of these intermediate periods , you have some foreign rule . but just to get a sense of some of what happened over this thousands of years , and i 'm kind of laughing in my head because it 's hard to cover over two , 3,000 years , in the course of just a few minutes , but this will give you a sense of what ancient egyptian civilization was all about . now the kings are referred to as pharaohs but as we 'll see that term pharaoh is not really used until we get to the new kingdom . but i will refer to the kings as pharaohs throughout this video , just to say , hey these are the egyptian kings . and the old kingdom is probably most known today in our popular culture for what we most associate with ancient egypt and that is the pyramids . and here , right over here are the pyramids , there 's the great pyramid of giza , which is near modern-day cairo today . this is the sphinx and they were built in that old period under the pharaohs sneferu and khufu , right over here in the 26th century bce . and we are still trying to get a better understanding of how this was done . we actually now do n't believe that it was done by slave labor , but instead it was done during , you could say , the off season by the peasants as a form of taxation . okay , you 're done planting or harvesting your crops ? well now that you have some time , and this shows actually the importance of agriculture for freeing people up , so to speak , why do n't you help the pharaohs built these massive tombs , which i 've seen various estimates that it might have taken some place between 10 and 100,000 people several decades to build each . but these are even today , these were built over 4,500 years ago , are some of the most iconic symbols that humanity has ever created . and the reason why we know so much about ancient egypt is that we have been able to decipher their writing . it 's a symbolic , they have these pictographs , these hieroglyphics , i 'm sure you 've heard of the word before , and for a while we had no idea what they said . we would see these encryptions in these tombs and we had a sense that , okay these tombs , especially things like the pyramids would be for these great kings , we could tell that it was a stratified society , that nobility had better tombs than others , but we did n't really have a good sense of what was going on until we discovered this , which is the rosetta stone , which was discovered in 1799 . the reason why this is so valuable is it has the same text written in three different languages . it has it written in the hieroglyphs of the ancient egyptians , and it has it written in a later script used in egypt , called demotic egyptian , and most importantly , it has it also written in greek . and so historians were able to say , okay , we can now start to decipher what these symbols mean because we have a translation of them and that 's why it 's one of the first civilizations where we 're able to put the picture together . and hieroglyphics are one of the first forms of writing . but let 's now go on in our journey through thousands of years of ancient egyptian civilization . between the old kingdom and the middle kingdom , you have the first intermediate period and then you have the middle kingdom and then you have the hyksos , which are semitic people , semitic referring to their language being of the same family as semitic languages like arabic , or hebrew , or aramaic . but then you have the new kingdom , and the new kingdom is considered to be the peak of ancient egypt . it 's really the height of their technology , it 's the height of their military capability . and there are several pharaohs that are worthy of note in the new kingdom . the first is , he was born amenhotep or he was originally known as amenhotep the fourth and then he eventually names himself akhenaton and akhenaton means effective for aton , aton being a significant egyptian god . and the reason why he changed his name is he decides that , okay we have , the egyptians have this huge pantheon of gods . here is just the some of them right over here , this is the god osiris , often associated with the afterlife or transition , regeneration , resurrection . you have the god amun here and his first name amenhotep , it means amun is satisfied . what is considered kind of the equivalent of zeus , you have the god here horus , once again a very significant god at different times in egypt , but what was interesting about amenhotep the fourth or akhenaton , whichever name you want to use , is he decided , no , no , no , i do n't like this pantheon , this polytheistic religion that we have , i wan na worship one god , and the god that he decides to worship is really the , you could consider it the sun god , or the sun disc , and its representation looks something like this and it was referred to as aten and so he changes his name to akhenaton and he actually starts to try to get rid of evidence of these other gods or to make them a lot less important . and so the reason why that 's notable is this is viewed as perhaps one of the first attempts at monotheism , at least within this ancient egyptian civilization . he 's also noted for giving a lot of power to his wife , to the queen , nefertiti , who some people say was second in command , or even co-ruled alongside him . now he was also famous because after his death , eventually , his son , king tut , tutankhamen , comes to power . and the reason why king tut , as he 's often known , although it 's tutankhamen , is known is because we were able to find his tombs in relatively good order and so he 's become a popular part of the imagination . and he 's known as a child pharaoh . he comes to power when he 's very young , he dies at 18 and so it 's kind of an interesting story . now , most prominent amongst all of the pharaohs across egyptian history , and this is also in the new kingdom , comes a little bit after tutankhamen , is ramses the second . and ramses the second , who emerges here in the 13th century , and he rules for most of the 13th century bce , he represents really the peak of egypt , ancient egypt , as a military power . he 's famous for the battle at kaddish , which is the earliest battle where we actually know what the tactics and the formations were and it was with the also significant hittite empire in 1274 bce , this is an image drawn much , much later , of the battle of kaddish . the battle , we now believe , might have been a bit of a stalemate , ramses the second was n't able to capture kaddish , but has told us a lot about military tactics and strategy and formation of that time . historians today think it might have been the largest chariot battle maybe ever . so this was a significant thing that happened . now , eventually the new kingdom does collapse , as we get to the end of the second millennium , and then over the next several hundreds of years , we 're talking about a very long period of time , it gets fragmented , you have several rulers , you have the kushites rule from the upper nile , the kushites were in this area right over here . they rule for a brief period . the assyrians , that 's a mesopotamian civilization , they rule for a small period of time , and then eventually and we talk about this in some detail in other videos , you have the persians take over , you have cambyses , cyrus the great 's son , he 's able to rule over , he 's able to conquer egypt and egypt becomes part of the achaemenid empire for a while until the conquering of alexander the great . and after alexander the great dies , one of his generals and his dynasty takes over , ptolemaic egypt and now it 's being ruled by foreigners , well it 's been ruled by foreigners for a while now , but now it 's by the greeks and the famous cleopatra , who 's considered a pharaoh of egypt , she 's actually greek by blood , she 's actually the one that seduced you could say julius cesar and marc antony and after cleopatra 's death , more and more , actually eventually it becomes part of rome . so as you can see we covered this enormous large time period in history , one of the most significant civilizations in all of history , one of the most famous poems about civilizations and rulers , about ramses the second , the poem ozymandias was named after him . you have some of the great cities of the ancient world , thebes , which was the capital during parts of the new kingdom and the middle kingdom , you have memphis , which was one of the , some people say founded by menes and the capital of the old kingdom . these were all happening in ancient egypt .

you have some of the great cities of the ancient world , thebes , which was the capital during parts of the new kingdom and the middle kingdom , you have memphis , which was one of the , some people say founded by menes and the capital of the old kingdom . these were all happening in ancient egypt .

how and why did ancient egyptians start believing in their religious system ?

in this video , we are going to give ourselves an overview of ancient egypt , which corresponds geographically pretty closely to the modern day state of egypt in northeast africa . now the central feature in both ancient egypt and in modern egypt is the nile river that you see in blue right over here . and the nile river is one of the great rivers of the world . it rivals the amazon river as the longest river and it sources the tributaries of the nile rover start even south of this picture and the water flows northward and eventually its delta reaches the mediterranean sea . the delta , which is where a river opens into the sea , is called a delta because , as you can see , these rivers , you can even see it from the satellite pictures right over here , they start branching up a bunch and you have this upside down triangular region , which looks a little bit like an upside down greek letter delta , so that 's why river delta is called that . and this one just happens to be upside down . if it was flowing the other way , it would be a right-side-up delta . so the nile river , it flows from , you could say , eastern mid-africa up into the mediterranean sea and because it has this northward flow , the southern parts of the river are upriver and they are actually called the upper nile . so , upper . the upper nile is actually south of the lower nile , of the lower nile . and once again , that 's because the upper nile is up river , it 's also flowing from higher elevations to lower elevations . so as you go south , you get to higher and higher elevations . now , the reason why the river is so important , we studied this multiple times , rivers are a source of fresh water , when they flood they make the surrounding soil fertile , they 're suitable for agriculture , and the nile valley is one of the first places that we see agriculture emerging during the neolithic period . in fact , human settlement we believe was along this nile river valley as far as 6,000 bce or 8,000 years ago , and it might have been there even further back in time . and because you have that agriculture , it allowed for higher population densities , which allowed for more specialization of labor and more complex societies . it 's not a coincidence that some of the first , that one of the first great civilizations emerged here . now , the story of the nile river , or of egypt , and actually they are tied very closely , even though egypt is considered a lot of this region , most of the human population , this is true even today , is right along the river , around that fertile soil , where the agriculture actually occurs . in fact , this was so important to the ancient egyptians that their whole calendar , their seasons , were based on what the nile river was doing . they had a season called the inundation , or the flooding of the river , which makes the soil fertile . they had a season of growth , which is now talking about the growth of the crops and they had a season of harvest . and so you had people in this valley for thousands of years , but when we talk about ancient egypt , we formally talk about it as a civilization around 3,100 , 3,150 bce . and this is where we get to our timeline right over here . so we 're talking about right around there on our timeline and the reason why this is considered the beginning of the ancient egyptian civilization is this is when we believe that upper and lower egypt were first united under the king and there 's different names used , narmer sometimes or menes . i 'm going to mispronounce things every now and then and i 'm probably doing it here as well . and so he was the king that unified upper and lower egypt into an empire and the empire , as we will see , which lasted thousands of years , every one of these spaces is a hundred years . we 're gon na go over huge time span , but the ancient egyptian civilization is roughly divided into three kingdoms . you have the old kingdom , which went from about , right from about the 27th century bce up to about the 17th century bce . you have the middle kingdom and you have the new kingdom . and once again , this is spanning right over here over a thousand years of history . and in between those , you have these intermediate periods where the kingdom or the empire was a little bit more fragmented . you have in some of these intermediate periods , you have some foreign rule . but just to get a sense of some of what happened over this thousands of years , and i 'm kind of laughing in my head because it 's hard to cover over two , 3,000 years , in the course of just a few minutes , but this will give you a sense of what ancient egyptian civilization was all about . now the kings are referred to as pharaohs but as we 'll see that term pharaoh is not really used until we get to the new kingdom . but i will refer to the kings as pharaohs throughout this video , just to say , hey these are the egyptian kings . and the old kingdom is probably most known today in our popular culture for what we most associate with ancient egypt and that is the pyramids . and here , right over here are the pyramids , there 's the great pyramid of giza , which is near modern-day cairo today . this is the sphinx and they were built in that old period under the pharaohs sneferu and khufu , right over here in the 26th century bce . and we are still trying to get a better understanding of how this was done . we actually now do n't believe that it was done by slave labor , but instead it was done during , you could say , the off season by the peasants as a form of taxation . okay , you 're done planting or harvesting your crops ? well now that you have some time , and this shows actually the importance of agriculture for freeing people up , so to speak , why do n't you help the pharaohs built these massive tombs , which i 've seen various estimates that it might have taken some place between 10 and 100,000 people several decades to build each . but these are even today , these were built over 4,500 years ago , are some of the most iconic symbols that humanity has ever created . and the reason why we know so much about ancient egypt is that we have been able to decipher their writing . it 's a symbolic , they have these pictographs , these hieroglyphics , i 'm sure you 've heard of the word before , and for a while we had no idea what they said . we would see these encryptions in these tombs and we had a sense that , okay these tombs , especially things like the pyramids would be for these great kings , we could tell that it was a stratified society , that nobility had better tombs than others , but we did n't really have a good sense of what was going on until we discovered this , which is the rosetta stone , which was discovered in 1799 . the reason why this is so valuable is it has the same text written in three different languages . it has it written in the hieroglyphs of the ancient egyptians , and it has it written in a later script used in egypt , called demotic egyptian , and most importantly , it has it also written in greek . and so historians were able to say , okay , we can now start to decipher what these symbols mean because we have a translation of them and that 's why it 's one of the first civilizations where we 're able to put the picture together . and hieroglyphics are one of the first forms of writing . but let 's now go on in our journey through thousands of years of ancient egyptian civilization . between the old kingdom and the middle kingdom , you have the first intermediate period and then you have the middle kingdom and then you have the hyksos , which are semitic people , semitic referring to their language being of the same family as semitic languages like arabic , or hebrew , or aramaic . but then you have the new kingdom , and the new kingdom is considered to be the peak of ancient egypt . it 's really the height of their technology , it 's the height of their military capability . and there are several pharaohs that are worthy of note in the new kingdom . the first is , he was born amenhotep or he was originally known as amenhotep the fourth and then he eventually names himself akhenaton and akhenaton means effective for aton , aton being a significant egyptian god . and the reason why he changed his name is he decides that , okay we have , the egyptians have this huge pantheon of gods . here is just the some of them right over here , this is the god osiris , often associated with the afterlife or transition , regeneration , resurrection . you have the god amun here and his first name amenhotep , it means amun is satisfied . what is considered kind of the equivalent of zeus , you have the god here horus , once again a very significant god at different times in egypt , but what was interesting about amenhotep the fourth or akhenaton , whichever name you want to use , is he decided , no , no , no , i do n't like this pantheon , this polytheistic religion that we have , i wan na worship one god , and the god that he decides to worship is really the , you could consider it the sun god , or the sun disc , and its representation looks something like this and it was referred to as aten and so he changes his name to akhenaton and he actually starts to try to get rid of evidence of these other gods or to make them a lot less important . and so the reason why that 's notable is this is viewed as perhaps one of the first attempts at monotheism , at least within this ancient egyptian civilization . he 's also noted for giving a lot of power to his wife , to the queen , nefertiti , who some people say was second in command , or even co-ruled alongside him . now he was also famous because after his death , eventually , his son , king tut , tutankhamen , comes to power . and the reason why king tut , as he 's often known , although it 's tutankhamen , is known is because we were able to find his tombs in relatively good order and so he 's become a popular part of the imagination . and he 's known as a child pharaoh . he comes to power when he 's very young , he dies at 18 and so it 's kind of an interesting story . now , most prominent amongst all of the pharaohs across egyptian history , and this is also in the new kingdom , comes a little bit after tutankhamen , is ramses the second . and ramses the second , who emerges here in the 13th century , and he rules for most of the 13th century bce , he represents really the peak of egypt , ancient egypt , as a military power . he 's famous for the battle at kaddish , which is the earliest battle where we actually know what the tactics and the formations were and it was with the also significant hittite empire in 1274 bce , this is an image drawn much , much later , of the battle of kaddish . the battle , we now believe , might have been a bit of a stalemate , ramses the second was n't able to capture kaddish , but has told us a lot about military tactics and strategy and formation of that time . historians today think it might have been the largest chariot battle maybe ever . so this was a significant thing that happened . now , eventually the new kingdom does collapse , as we get to the end of the second millennium , and then over the next several hundreds of years , we 're talking about a very long period of time , it gets fragmented , you have several rulers , you have the kushites rule from the upper nile , the kushites were in this area right over here . they rule for a brief period . the assyrians , that 's a mesopotamian civilization , they rule for a small period of time , and then eventually and we talk about this in some detail in other videos , you have the persians take over , you have cambyses , cyrus the great 's son , he 's able to rule over , he 's able to conquer egypt and egypt becomes part of the achaemenid empire for a while until the conquering of alexander the great . and after alexander the great dies , one of his generals and his dynasty takes over , ptolemaic egypt and now it 's being ruled by foreigners , well it 's been ruled by foreigners for a while now , but now it 's by the greeks and the famous cleopatra , who 's considered a pharaoh of egypt , she 's actually greek by blood , she 's actually the one that seduced you could say julius cesar and marc antony and after cleopatra 's death , more and more , actually eventually it becomes part of rome . so as you can see we covered this enormous large time period in history , one of the most significant civilizations in all of history , one of the most famous poems about civilizations and rulers , about ramses the second , the poem ozymandias was named after him . you have some of the great cities of the ancient world , thebes , which was the capital during parts of the new kingdom and the middle kingdom , you have memphis , which was one of the , some people say founded by menes and the capital of the old kingdom . these were all happening in ancient egypt .

he 's also noted for giving a lot of power to his wife , to the queen , nefertiti , who some people say was second in command , or even co-ruled alongside him . now he was also famous because after his death , eventually , his son , king tut , tutankhamen , comes to power . and the reason why king tut , as he 's often known , although it 's tutankhamen , is known is because we were able to find his tombs in relatively good order and so he 's become a popular part of the imagination .

why did king tut die at such a young age ?

in this video , we are going to give ourselves an overview of ancient egypt , which corresponds geographically pretty closely to the modern day state of egypt in northeast africa . now the central feature in both ancient egypt and in modern egypt is the nile river that you see in blue right over here . and the nile river is one of the great rivers of the world . it rivals the amazon river as the longest river and it sources the tributaries of the nile rover start even south of this picture and the water flows northward and eventually its delta reaches the mediterranean sea . the delta , which is where a river opens into the sea , is called a delta because , as you can see , these rivers , you can even see it from the satellite pictures right over here , they start branching up a bunch and you have this upside down triangular region , which looks a little bit like an upside down greek letter delta , so that 's why river delta is called that . and this one just happens to be upside down . if it was flowing the other way , it would be a right-side-up delta . so the nile river , it flows from , you could say , eastern mid-africa up into the mediterranean sea and because it has this northward flow , the southern parts of the river are upriver and they are actually called the upper nile . so , upper . the upper nile is actually south of the lower nile , of the lower nile . and once again , that 's because the upper nile is up river , it 's also flowing from higher elevations to lower elevations . so as you go south , you get to higher and higher elevations . now , the reason why the river is so important , we studied this multiple times , rivers are a source of fresh water , when they flood they make the surrounding soil fertile , they 're suitable for agriculture , and the nile valley is one of the first places that we see agriculture emerging during the neolithic period . in fact , human settlement we believe was along this nile river valley as far as 6,000 bce or 8,000 years ago , and it might have been there even further back in time . and because you have that agriculture , it allowed for higher population densities , which allowed for more specialization of labor and more complex societies . it 's not a coincidence that some of the first , that one of the first great civilizations emerged here . now , the story of the nile river , or of egypt , and actually they are tied very closely , even though egypt is considered a lot of this region , most of the human population , this is true even today , is right along the river , around that fertile soil , where the agriculture actually occurs . in fact , this was so important to the ancient egyptians that their whole calendar , their seasons , were based on what the nile river was doing . they had a season called the inundation , or the flooding of the river , which makes the soil fertile . they had a season of growth , which is now talking about the growth of the crops and they had a season of harvest . and so you had people in this valley for thousands of years , but when we talk about ancient egypt , we formally talk about it as a civilization around 3,100 , 3,150 bce . and this is where we get to our timeline right over here . so we 're talking about right around there on our timeline and the reason why this is considered the beginning of the ancient egyptian civilization is this is when we believe that upper and lower egypt were first united under the king and there 's different names used , narmer sometimes or menes . i 'm going to mispronounce things every now and then and i 'm probably doing it here as well . and so he was the king that unified upper and lower egypt into an empire and the empire , as we will see , which lasted thousands of years , every one of these spaces is a hundred years . we 're gon na go over huge time span , but the ancient egyptian civilization is roughly divided into three kingdoms . you have the old kingdom , which went from about , right from about the 27th century bce up to about the 17th century bce . you have the middle kingdom and you have the new kingdom . and once again , this is spanning right over here over a thousand years of history . and in between those , you have these intermediate periods where the kingdom or the empire was a little bit more fragmented . you have in some of these intermediate periods , you have some foreign rule . but just to get a sense of some of what happened over this thousands of years , and i 'm kind of laughing in my head because it 's hard to cover over two , 3,000 years , in the course of just a few minutes , but this will give you a sense of what ancient egyptian civilization was all about . now the kings are referred to as pharaohs but as we 'll see that term pharaoh is not really used until we get to the new kingdom . but i will refer to the kings as pharaohs throughout this video , just to say , hey these are the egyptian kings . and the old kingdom is probably most known today in our popular culture for what we most associate with ancient egypt and that is the pyramids . and here , right over here are the pyramids , there 's the great pyramid of giza , which is near modern-day cairo today . this is the sphinx and they were built in that old period under the pharaohs sneferu and khufu , right over here in the 26th century bce . and we are still trying to get a better understanding of how this was done . we actually now do n't believe that it was done by slave labor , but instead it was done during , you could say , the off season by the peasants as a form of taxation . okay , you 're done planting or harvesting your crops ? well now that you have some time , and this shows actually the importance of agriculture for freeing people up , so to speak , why do n't you help the pharaohs built these massive tombs , which i 've seen various estimates that it might have taken some place between 10 and 100,000 people several decades to build each . but these are even today , these were built over 4,500 years ago , are some of the most iconic symbols that humanity has ever created . and the reason why we know so much about ancient egypt is that we have been able to decipher their writing . it 's a symbolic , they have these pictographs , these hieroglyphics , i 'm sure you 've heard of the word before , and for a while we had no idea what they said . we would see these encryptions in these tombs and we had a sense that , okay these tombs , especially things like the pyramids would be for these great kings , we could tell that it was a stratified society , that nobility had better tombs than others , but we did n't really have a good sense of what was going on until we discovered this , which is the rosetta stone , which was discovered in 1799 . the reason why this is so valuable is it has the same text written in three different languages . it has it written in the hieroglyphs of the ancient egyptians , and it has it written in a later script used in egypt , called demotic egyptian , and most importantly , it has it also written in greek . and so historians were able to say , okay , we can now start to decipher what these symbols mean because we have a translation of them and that 's why it 's one of the first civilizations where we 're able to put the picture together . and hieroglyphics are one of the first forms of writing . but let 's now go on in our journey through thousands of years of ancient egyptian civilization . between the old kingdom and the middle kingdom , you have the first intermediate period and then you have the middle kingdom and then you have the hyksos , which are semitic people , semitic referring to their language being of the same family as semitic languages like arabic , or hebrew , or aramaic . but then you have the new kingdom , and the new kingdom is considered to be the peak of ancient egypt . it 's really the height of their technology , it 's the height of their military capability . and there are several pharaohs that are worthy of note in the new kingdom . the first is , he was born amenhotep or he was originally known as amenhotep the fourth and then he eventually names himself akhenaton and akhenaton means effective for aton , aton being a significant egyptian god . and the reason why he changed his name is he decides that , okay we have , the egyptians have this huge pantheon of gods . here is just the some of them right over here , this is the god osiris , often associated with the afterlife or transition , regeneration , resurrection . you have the god amun here and his first name amenhotep , it means amun is satisfied . what is considered kind of the equivalent of zeus , you have the god here horus , once again a very significant god at different times in egypt , but what was interesting about amenhotep the fourth or akhenaton , whichever name you want to use , is he decided , no , no , no , i do n't like this pantheon , this polytheistic religion that we have , i wan na worship one god , and the god that he decides to worship is really the , you could consider it the sun god , or the sun disc , and its representation looks something like this and it was referred to as aten and so he changes his name to akhenaton and he actually starts to try to get rid of evidence of these other gods or to make them a lot less important . and so the reason why that 's notable is this is viewed as perhaps one of the first attempts at monotheism , at least within this ancient egyptian civilization . he 's also noted for giving a lot of power to his wife , to the queen , nefertiti , who some people say was second in command , or even co-ruled alongside him . now he was also famous because after his death , eventually , his son , king tut , tutankhamen , comes to power . and the reason why king tut , as he 's often known , although it 's tutankhamen , is known is because we were able to find his tombs in relatively good order and so he 's become a popular part of the imagination . and he 's known as a child pharaoh . he comes to power when he 's very young , he dies at 18 and so it 's kind of an interesting story . now , most prominent amongst all of the pharaohs across egyptian history , and this is also in the new kingdom , comes a little bit after tutankhamen , is ramses the second . and ramses the second , who emerges here in the 13th century , and he rules for most of the 13th century bce , he represents really the peak of egypt , ancient egypt , as a military power . he 's famous for the battle at kaddish , which is the earliest battle where we actually know what the tactics and the formations were and it was with the also significant hittite empire in 1274 bce , this is an image drawn much , much later , of the battle of kaddish . the battle , we now believe , might have been a bit of a stalemate , ramses the second was n't able to capture kaddish , but has told us a lot about military tactics and strategy and formation of that time . historians today think it might have been the largest chariot battle maybe ever . so this was a significant thing that happened . now , eventually the new kingdom does collapse , as we get to the end of the second millennium , and then over the next several hundreds of years , we 're talking about a very long period of time , it gets fragmented , you have several rulers , you have the kushites rule from the upper nile , the kushites were in this area right over here . they rule for a brief period . the assyrians , that 's a mesopotamian civilization , they rule for a small period of time , and then eventually and we talk about this in some detail in other videos , you have the persians take over , you have cambyses , cyrus the great 's son , he 's able to rule over , he 's able to conquer egypt and egypt becomes part of the achaemenid empire for a while until the conquering of alexander the great . and after alexander the great dies , one of his generals and his dynasty takes over , ptolemaic egypt and now it 's being ruled by foreigners , well it 's been ruled by foreigners for a while now , but now it 's by the greeks and the famous cleopatra , who 's considered a pharaoh of egypt , she 's actually greek by blood , she 's actually the one that seduced you could say julius cesar and marc antony and after cleopatra 's death , more and more , actually eventually it becomes part of rome . so as you can see we covered this enormous large time period in history , one of the most significant civilizations in all of history , one of the most famous poems about civilizations and rulers , about ramses the second , the poem ozymandias was named after him . you have some of the great cities of the ancient world , thebes , which was the capital during parts of the new kingdom and the middle kingdom , you have memphis , which was one of the , some people say founded by menes and the capital of the old kingdom . these were all happening in ancient egypt .

you have the god amun here and his first name amenhotep , it means amun is satisfied . what is considered kind of the equivalent of zeus , you have the god here horus , once again a very significant god at different times in egypt , but what was interesting about amenhotep the fourth or akhenaton , whichever name you want to use , is he decided , no , no , no , i do n't like this pantheon , this polytheistic religion that we have , i wan na worship one god , and the god that he decides to worship is really the , you could consider it the sun god , or the sun disc , and its representation looks something like this and it was referred to as aten and so he changes his name to akhenaton and he actually starts to try to get rid of evidence of these other gods or to make them a lot less important . and so the reason why that 's notable is this is viewed as perhaps one of the first attempts at monotheism , at least within this ancient egyptian civilization .

is n't aten also known as ra , or the god of the sun ?