Sense Organs Sense Organs There are five senses: sight, hearing, taste, smell and touch. There are organs connected with these sense that take in information that is sent to the brain so that the body can act on it. Sight The eye is the organ of the sense of sight. Eyes detect light, and convert it to electro-chemical impulses in neurons. Parts of the eye: Cornea The transparent window at the front of the eye which is covered in a thin layer of tears. Aqueous humor On the other side of the cornea is more moisture. This clear, watery fluid is the aqueous humor. It circulates throughout the front part of the eye and keeps a constant pressure within the eye. Pupil and iris: The pupil is the circular opening in the colored part of the eye which is the iris. The iris dilates or opens and contracts to let in more or less light. Lens: Resembles the lens of a camera and focuses the light, changing shape as it takes in light reflected from objects near and far. Vitreous: A clear jelly that the focused light passes through to the retina. Retina: The inner lining at the back of the eye.

It contains blood vessels which bring nutrients to the nerve cells. The macula is at the very center of the retina and contains the fovea. The photoreceptors of the retina are the rods and cones. The cones perceive color and finer elements. The retinal pigment epithelium, choroid and sclera are three more layers. The photoreceptors send light and images to a large nerve called the optic nerve. This carries the information to the occipital lobe of the brain where they are interpreted. Eyelids and eyelashes: These protect the eye and along with tears keep the eye clear and moist. Hearing The ear is the organ concerned with hearing. The ear has three parts: the outer ear, the middle ear and the inner ear. Outer ear: Pinna: The outermost part of the ear made of cartilage that is connected to the outer tube called the auditory canal. This leads to the eardrum. Middle Ear Eardrum, stirrup, anvil and hammer: This membrane vibrates and along with the three tiny bones in the middle ear, the hammer, anvil and stirrup, and sends the stiumuli to the cochlea.

Is spiral shaped and it transforms sound into nerve impulses that travel to the brain. Semicircular canals: These fluid filled tubes attach to the cochlea and nerves in the inner ear. They send information on balance and head position to the brain. Eustachian tube: Drains fluid from the middle ear into the throat behind the nose. Taste: Tongue: Is a muscular organ in the mouth. The tongue is covered with moist, pink tissue called mucosa and tiny bumps called papillae. Thousands of taste buds cover the surfaces of the papillae. Taste buds are collections of nerve-like cells that connect to nerves going into the brain. There are four types of taste buds: sour, sweet, bitter and salty. The tongue is vital in tasting and chewing food and in speech. Smell: Nose: The nose, along with the mouth, lets air in and out of the body. It also helops us distinguish different smells in that air. The nasal root is the top of the nose, forming an indentation at the suture where the nasal bones meet the frontal bone.

The anterior nasal spine is the thin projection of bone at the midline on the lower nasal margin, holding the cartilaginous center of the nose.[1] Adult humans have nasal hairs in the anterior nasal passage. Touch Skin: The skin is the largest organ of the body, with a total area of about 20 square feet. The skin protects us from microbes and the elements, helps regulate body temperature, and permits the sensations of touch, heat, and cold. The epidermis, the outermost layer of skin, provides a waterproof barrier and creates our skin tone. Layers: The dermis, beneath the epidermis, contains tough connective tissue, hair follicles, and sweat glands. The deeper subcutaneous tissue (hypodermis) is made of fat and connective tissue. The skin's color is created by special cells called melanocytes, which produce the pigment melanin. Melanocytes are located in the epidermis. Neuroscience for Kids - Animal Senses Has chemoreceptors (taste receptors) on its feet. The butterfly has hairs on its wings to detect changes in air pressure. Using vision, the butterfly Colias can distinguish two points separated by as little as 30 microns.

(Humans can distinuguish two points separated by 100 microns.) Buzzard Retina has 1 million photoreceptors per sq. mm. Can see small rodents from a height of 15,000 ft. Cat Has hearing range between 100 and 60,000 Hz. Olfactory membrane about 14 sq. cm. For comparison, humans have an olfactory membrane of about 4 sq. cm. Chameleon The eyes of the chameleon can move independently. Therefore, it can see in two different directions at the same time. Cockroach Can detect movement as small as 2,000 times the diameter of a hydrogen atom. Crab Has hairs on claws and other parts of the body to detect water current and vibration. Many crabs have their eyes on the end of stalks. Crayfish Has sensory hairs that can detect movement of 0.1 microns (at 100 Hz frequency). Cricket Can hear using their legs; sound waves vibrate a thin membrane on the cricket's front legs. Dog Has olfactory membrane up to 150 sq. cm.

Can hear sound as high as 40,000 Hz. Dolphin Like bats, dolphins use echolocation for movement and locating objects. Can hear frequencies up to at least 100,000 Hz. Dragonfly Entire body covered with chemoreceptors (taste receptors). Eagle Eyeball length = 35 mm (human eyeball length = 24 mm) Visual acuity is 2.0 to 3.6 times better (depending on the type of eagel) than that of humans. (Shlaer, R., An eagle's eye: quality of the retinal image, Science, 176:920-922, 1972.) Elephant Has hearing range between 1 and 20,000 Hz. The very low frequency sounds are in the "infrasound" range. Humans cannot hear sounds in the infrasound range. Falcon Can see a 10 cm. object from a distance of 1.5 km. Visual acuity is 2.6 times better than human.

(Garcia et al., Falcon visual acuity, Science, 192:263-265, 1976.) Can see sharp images even when diving at 100 miles/hr. Fish Some can detect the L-serine (a chemical found in the skin of mammals) diluted to 1 part per billion. Have a "lateral line" system consisting of sense organs ("neuromasts") in canals along the head and trunk. These receptors are used to detect changes in water pressure and may be used to locate prey and aid movement. Some fish can see into the infrared wavelength of the electromagnetic spectrum. Fish (Catfish) Has 3 or 4 pairs of whiskers, called barbels, to find food. The catfish also has approximately 100,000 taste buds. (Humans have only 10,000 taste buds.) Fish (Deep sea) Only have rods in the retina: 25 million rods/sq. mm. Perhaps they need this high density of photoreceptors to detect the dim biolumninescence that exists in the ocean depths. Fish (Drum Fish) Collects underwater sound vibrations with an air bladder.

The signals are then sent from the air bladder to the "weberian apparatus" in the middle ear and then to the inner ear. Hair cells in the inner ear respond to the vibration and transmit sound information to the fish brain. Fish ("Four-eyed Fish" Anableps microlepis) Can see in air and water simultaneously. Each eye is divided by flaps, so there is one opening in the air and one in the water. Fly Each eye has 3,000 lenses. (Simmons and Young, 1999) Eye has a flicker fusion rate of 300/sec. Humans have a flicker fusion rate of only 60/sec in bright light and 24/sec in dim light. The flicker fusion rate is the frequency with which the "flicker" of an image cannot be distinguished as an individual event. Like the frame of a movie...if you slowed it down, you would see individual frames. Speed it up and you see a constantly moving image. The small parasitic fly (Ormia ochracea) can locate sounds within a range of only 2o of the midline.

(Mason et al., Nature, 410:686-690, 2001) Blowflies taste with 3,000 sensory hairs on their feet. Frog Has an eardrum (tympanic membrane) on the outside of the body behind the eye. Giant Squid Eye is 25 cm in diameter. Retina can contain up to 1 billion photoreceptors. Grasshopper Has hairs ("sensilla") all over the body to detect air movement. Can hear up to 50,000 Hz. Hawk Normal vision for people is 20/20. A hawk's vision is equivalent to 20/5. This means that the hawk can see from 20 feet what most people can see from 5 feet. (Scientific American, April 2001, page 24) Hawk Buteo Has 1 million photoreceptor per square millimeter in its retina. Iguana Able to detect the temperature of sand within 2 degrees F. This temperature is needed for the iguana to lay its eggs. Jellyfish The box jellyfish has 24 eyes.

(Nature, 435:201-205, 2005.) Mice Can hear frequencies between 1,000 and 100,000 Hz. By comparison, humans can hear frequencies between 20 and 20,000 Hz. Star-nosed Mole Uses its fleshy star nose for hunting. The Star-nosed mole has 100,000 nerve fibers that run from star to the brain. This is almost six times more than the touch receptors in the human hand. Mosquito Attracted to host by human body odor (especially foot odor), carbon dioxide, body heat and body humidity. Moth Noctuid Moth has a hearing range between 1,000 and 240,000 Hz. Emperor Moth can detect pheromones up to 5 km. distant. Silkworm Moth can detect pheromones up to 11 km. distant. This moth can detect pheromones in concentrations as low as 1 molecule of pheromone per 1017 molecules of air.

A receptor cell can respond to a single molecule of the pheromone called bombykol and 200 molecules can cause a behavioral response. Octopus Retina contains 20 million photoreceptors. The eye has a flicker fusion frequency of 70/sec in bright light. The pupil of the eye is rectangular. Has chemoreceptors (taste receptors) on the suckers of their tentacles. By tasting this way, an octopus does not have to leave the safety of its home. Penguin Has a flat cornea that allows for clear vision underwater. Penguins can also see into the ultraviolet range of the electromagnetic spectrum. Pig Tongue contains 15,000 taste buds. For comparison, the human tongue has 9,000 taste buds. Pigeon With eyes mounted laterally on their heads, pigeons can view 340 degrees...everywhere except in back of their heads. Can detect sounds as low as 0.1 Hz. Platypus Has electric sensors in its bill that can detect 0.05 microvolts. Other receptors in the bill are for touch and temperature detection.

The cochlea of the inner ear is coiled only a quarter of a turn. In man, the cochlea is coiled about 2.7 times. Rabbit Tongue contains 17,000 taste buds. Rat Has hearing range between 1,000 and 90,000 Hz. Seahorse Each eye can move independently. Scallop Has 100 eyes around the edge of the shell. These eyes are probably used to detect shadows of predators such as the starfish. Scorpion Can detect air moving at only 0.072 km/hr with special hairs on its pincers. Can have as many as 12 eyes. Shark Has specialized electrosensing receptors with thresholds as low as 0.005 uV/cm. These receptors may be used to locate prey. The dogfish can detect a flounder that is buried under the sand and emitting 4 uAmp of current. Some sharks can detect fish extracts as concentrations lower than one part in 10 billion. Some sharks sense light directly through the skull by the pineal body. The thresher shark has an eye up to 5 inches (12.5 cm) in diameter.

The last three facts are from D.Perrine, Sharks and Rays of the World, Stillwater: Voyaguer Press, 1999. Snakes Pit-vipers have a heat-sensitive organ between the eyes and the nostrils about 0.5 cm deep. This organ has a membrane containing 7,000 nerve endings that respond to temperature changes as small as 0.002-0.003 degrees centigrade. A rattlesnake can detect a mouse 40 cm away if the mouse is 10 degrees centigrade above the outside temperature. The tongue of snakes has no taste buds. Instead, the tongue is used to bring smells and tastes into the mouth. Smells and tastes are then detected in two pits, called "Jacobson's organs", on the roof of their mouths. Receptors in the pits then transmit smell and taste information to the brain. Snakes have no external ears. Therefore, they do not hear the music of a "snake charmer". Instead, they are probably responding to the movements of the snake charmer and the flute. However, sound waves may travel through bones in their heads to the middle ear. Snakes have no moveable eyelids.

Instead, they have a clear, scale-like membrane covering the eye. Sparrow Retina has 400,000 photoreceptors per sq. mm. Spider Human Physiology - 10 Sense Organs Human Physiology Export (PDF) Sense Organs Overview:"Our perceptions of the world-its textures, colors, and sounds, its warmth, smells, and tastes-are created by the brain from electrochemical nerve impulses delivered to it from sensory receptors" (textbook). Our body is an amazing thing. It can perceive each of these senses and influence our likes and dislikes, the way we move around this world, and our thoughts on it. Major Concepts: Categories of Sensory Receptors:Sensory receptors are grouped by the type of stimulus they respond to. Chemoreceptors respond to chemical stimuli in the environment or within the blood. These would include taste buds, olfactory epithelium, and aortic and carotid bodies. Photoreceptors detect light. These would include the rods and cones within the retina of the eye. Thermoreceptors detect mechanical deformation of the receptor cell membrane, or touch and pressure. Nocireceptors are also known as pain receptors.

This type has a higher threshold to stimuli than do the other types. Sensory receptors can also be categorized by the type of information they send to the brain, such as proprioceptors, which tell body position and fine muscle movement. Muscle spindles, golgi tendon organs, and joint receptors would all be included in this type. Mechanoreceptors, thermoreceptors, and nociceptors are all grouped into the category Cutaneous, or skin, Receptors. Sight, hearing, and equilibrium are all grouped into another category titled the Special Sensors Category. Cutaneous Sensations:The dendritic nerve endings monitor the senses of touch, pressure, temperature, and pain. However, the nerve endings and structure are different for each sense. This table (also found in the Human Physiology textbook) breaks down the receptors by nerve endings, structure, sensation, and location. Cutaneous Receptors Dendrites encapsulated by concentric lamellae of connective tissue structures Deep pressure, fast vibrations Deep in the dermis It is amazing to see how many structures are involved so that we are able to detect different sensations.

A special receptor, capsaicin receptors, produce a pain sensation when hot temperatures are applied, therefore this serves as both and ion channel and a receptor for capsaicin. This is the same molecule that is found in chili peppers that would cause a hot and painful sensation. In response, these ion channels open causing Calcium and Sodium to diffuse into the neuron which sends an action potential to the brain. Other receptors detect pain sensations from cellular damage and during infection and inflammation. What Makes Us Taste, Smell, Hear, and See:Just like the receptors are all different for the cutaneous receptors, so are the ones that make up our ability to taste, smell, hear, and see. Have you ever had a head cold that made it impossible to smell which in turn, also made your food taste bland and tasteless? This is because taste and smell go hand-in-hand. Smell influences the way we taste since air molecules must be dissolved in fluid before smelling therefore being detected in gustatory receptors. Taste and smell are grouped under chemoreceptors. Receptors that respond to the internal environment are called interoreceptors and external ones are called exteroreceptors.

There are also taste, gustatory, receptors that detect chemicals in food and drinks and smell, olfactory, receptors that detect gasseous molecules in the air. Taste:Gustation, or sense of taste, is influenced by taste buds-barrel shaped receptors. Each of these taste buds contains 50-100 specialized epithelial cells that act as neurons and release neurotransmitters that activate sensory neurons for taste when stimulated. The facial nerve is associated with the taste buds located on the anterior two-thirds of the tongue. This sends touch and temperature sensations to the part of the cerebral cortex that is specialized in tongue sensations. The remaining posterior one-third is associated with the glossopharyngeal nerve. The epithelial cells, known as taste cells, found on the taste buds, produce different categories of taste depending on the chemicals that come into contact with them. The five categories of tastes include 1) Salty: The saltiness is contributed to the presence of sodium ions. 2) Sour: This taste in produced by hydrogen ions. Both salty and sour tastes pass through membrane channels which causes them to depolarize and release their neurotransmitters.

3) Sweet, 4) Bitter, and 5) Umami (meaning "savory") all bind to G-proteins to transmit their taste. Bitter is the most acute sensation and is associated with toxic materials. Umami, the newest discovery, sends a "meaty" sensation because of the proteins, specifically the amino acid L-glutamate and L-aspartate. This is the most favored taste along sweet. Smell:The olfactory epithelium is where the olfactory (smell) receptors are located. The olfactory apparatus contains receptor cells, supporting cells, and basal cells. Receptors cells are replaced every one to two months by basal cells due to environmental damage. The supporting cells make air molecules less lipid soluble to prevent them from entering the brain. Even after many neurons have mutated to prevent certain sensations from being expressed, every person still has roughly "300 genes that code for 300 different olfactory receptor proteins" (textbook). The odorant molecule binds to a receptor associated with three G-protein subunits, which then dissociate, move into the membrane, and activate adenylate which catalyzes ATP to cAMP.

This opens ion channels causing the diffusion of sodium and calcium in which stimulates action potentials. These then go to the olfactory bulb within the cerebral cortex for the smell to be identified. Hearing:Sound is measured in both frequency and intensity. Frequency, the number of cycles per second, is directly related to pitch, the depth of a sound or tone. In other words, the higher the frequency, the higher the pitch. Intensity, or loudness, is related to amplitude. So how are we able to hear what we hear? Sound waves are channeled into the ear by the auricle that leads into the external auditory canal (also known as the external auditory meatus). The sounds waves travel to the tympanic membrane, better known as the eardrum, causing it to vibrate. The malleus, which is attached to the eardrum, receives the eardrum causing it to also vibrate. This continues to the incus and to the stapes before it sends it off to the oval window, a membrane in the cochlea. The ossicles (malleua, incus, and stapes) helps protect the ear from loud noises which may damage the nerves located in the cochlea, or the hearing part of the ear.

The cochlea is a snail-like instrument in the inner ear that contains fluid which forms waves from the vibrations. The basilar membrane, a part of the cochlea, contains sensory hair cells. These hair cells bend as a result of movement of the basilar membrane. This causes an action potential to fire and to travel to the brain, via the vestibulocochlear nerve, for the sound to be interpreted. Here is a flow-chart to break down what was stated. Sounds waves enter the ear via the auricle that goes to the external auditory canal.The sound waves cause the eardrum to vibrate.The vibrations flow to the ossicles causing them to vibrate.The vibrations continue to the oval window in the cochlea.Vibrations form waves in the cochlea.These waves flow to the basilar membrane that contains hair cells.These hair cells bend stimulating an action potential. The action potential travels to the auditory cortex in the brain via the vestibulocochlear nerve. Sound is interpreted. Sight:Sight is limited to a small area on the back of the eye called the retina. The retina contains sepcialized structures called rods and cones.

Light rays travel through the sclera, the tough outer layer called "the whites of the eyes", through the cornea to the anterior chamber of the eye. This chamber contains a small opening called the pupil which light travels through before it hits the lens. The iris, or the colored part of the eye, surrounding the pupil, increases or decreases to let more light in or keep more out. The light then travels to the back of the eye, the retina, which contain photoreceptors. The image on the back of the eye is backward and upside down. The neurons stimulated, travel through the optic nerve to the brain where the image is flipped the right side up and forward and in interpreted. In order for the image to be presented, the light must hit the retina in the right spot. In order for this to be achieved, the light must be refracted, or bent. This is caused by the media which is dependent on the densities of the two media and the curvature of the interface between the media. The image perceived also relies on accommodation, "the ability of the eyes to keep the image focused on the retina as the distance between the eyes and object varies" (textbook). This relies on contraction and relaxation of the ciliary muscles.

Essential Questions:1) Use a flow chart to describe how sound waves in the air within the external auditory meatus are transduced into the movements of the basilar membrane (hair cells). - Described/shown above. 2) Describe how light is transmitted the the structures of the eye, refracted, and photoreceptors are stimulated to send the CNS to be interpreted. In other words, trace the path of light and the neural impulses sent to the brain. - Light travels through the sclera, cornea, anterior chamber, pupil, lens, and posterior chamber to the retina. The retina contains rods and cones which stimulate neurons. The right half of the visual field goes to the left half of the retinas and vice versa. Therefore, the left lateral geniculte nucleus receives input from the right halves of the visual field of both the eyes and vice versa. The input travels to the occipital lobe of the cerebrum or the visual cortex. Career Application:The senses can be an important aspect of nursing. Loss of any of the senses could be a sign of some disease. An example would be if someone came in complaining of loss of taste.

Although most often it isn't something serious, it could be a sign on Bell's Palsy, a disorder causing impairment of facial muscles. More test would be ran in order to confirm this. Although there are no treatments for this, we could prescribe eye drops if the eye muscles are having trouble closing to prevent eye dryness and damage. Another important aspect of knowing the senses would be if you worked in the OB department. When a new baby is born, their senses must be tested to make sure nothing is wrong. One of these being the hearing test. We would need to preform the hearing test to show that the baby does not have problems hearing. If the baby fails the hearing test three times, more tests must be ran. Sensory systems - Biology Online Sensory systems Sensory systems - The Human Physiology A sensory system is a part of nervous system consisting of sensory receptors that receive stimuli from internal and external environment, neural pathways that conduct this information to brain and parts of brain that processes this information. The information is called sensory information and it may or may not lead to conscious awareness. If it does, it can be called sensation. Receptors Specialized endings of afferent neurons or separate cells that affect ends of afferent neurons.

They collect information about external and internal environment in various energy forms-and energy that activates a receptor is called a stimulus. Stimulus energy is first transformed into graded or receptor potentials and the process by which a stimulus is transformed into an electrical response is called stimulus transduction. Each receptor is specific to a certain type of stimulus, which is called its adequate stimulus. Specificity also exists in the range of stimulus energies that the receptor responds to. However, a receptor can be activated by a nonspecific stimulus if its intensity is sufficiently high. Receptor Potential Gating of ion channels in specialized receptor membranes allows a change in ion fluxes across the membrane, generating a graded receptor potential. The graded potential initiates an action potential, frequency and NOT magnitude of which is determined by magnitude of the graded potential. Magnitude of the receptor potential is determined by stimulus strength, summation of receptor potentials, and receptor sensitivity. The decrease in sensitivity with a constant stimulus is called adaptation. Neural Pathways in Sensory Systems A single afferent neuron with all its receptor endings makes a sensory unit. When stimulated, this is the portion of body that leads to activity in a particular afferent neuron is called the receptive field of that neuron.

Afferent neurons enter the CNS, diverge and synapse upon many interneurons. These afferent neurons are called sensory or ascending pathways and specific ascending pathways if they carry information about a single type of stimulus. The ascending pathways reach the cerebral cortex on the side opposite to where their sensory receptors are located. Specific ascending pathways that transmit information from somatic receptors and taste buds go to somatosensory cortex (parietal lobe), the ones from eyes go to visual cortex (occipital lobe), and the ones from ears go to auditory cortex (temporal lobe). Olfaction is NOT represented in cerebral cortex. Nonspecific ascending pathways consist of polymodal neurons and are activated by sensory units of several types. These pathways are important in alertness and arousal. Cortical association areas, lying outside primary cortical sensory areas, participate in more complex analysis of incoming information such as comparison, memory, language, motivation, emotion etc. Primary Sensory Coding Sensory systems code 4 aspects of a stimulus: (1) Stimulus Type (modality). All receptors of a single afferent neuron are sensitive to the same type of stimulus. (2) Stimulus Intensity.

An increased stimulus results in a larger receptor potential,, leading to a higher frequency of action potential. Stronger stimuli also affect a larger area and recruit a larger number of receptors. (3) Stimulus Location. Coded by site of the stimulated receptor. The precision of location, called acuity, is negatively correlated with the amount of convergence in ascending pathways, size of the receptive field and overlap with adjacent receptive fields. Response is highest at the center of receptive field since receptor density is the highest there. Using lateral inhibition, a process by which information from neurons at the edge of a stimulus is inhibited, acuity can be increased. (4) Stimulus Duration. Rapid adapting receptors respond rapidly at the onset of stimulus but slow down or stop firing during the remainder of stimulus (they adapt quickly). They are important in signaling rapid change. Slow adapting receptors maintain their response at or near the initial level of firing through the duration of stimulus and are important in signaling slow changes. Somatic Sensation Sensations from skin, muscles, bone are initiated by somatic receptors. Receptors for visceral sensations are similar. Touch-Pressure Mechanoreceptors in the skin are of 2 types, rapid and slow adapting ones.

Posture and Movement Muscle-spindle stretch receptors, occurring in skeletal muscles respond to the absolute magnitude and the rate of muscle stretch. Mechanoreceptors in joints, tendons, ligaments and skin also participate. Temperature Thermoreceptors are of two types, one that responds to an increase and the other that responds to a decrease in temperature. Pain Nociceptors respond to intense mechanical deformation, excessive heat etc. which cause tissue damage and many chemicals that are released by damaged cells or cells of immune system. If the initial stimulus of pain leads to an increased sensitivity to subsequent painful stimuli it is called hyperalgesia. If descending pathways inhibit the transmission of pain stimuli, it leads to a suppression of pain and this is called stimulation-produced analgesia. If both visceral and somatic afferent converge on the same interneuron, excitation of one can lead to excitation of the other, leading to the pain being felt at a site different from the actual injured part. This is called referred pain. Stimulating non-pain afferent fibers can inhibit neurons in the pain pathway and this therapy is called transcutaneous electric nerve stimulation (TENS). Rubbing on a painful area and acupuncture work for the same reason.

Vision Optics Receptors in eye are sensitive to only the visible light of electromagnetic spectrum. Lens and cornea focus impinging light rays into an image at fovea centralis area of retina. Light passing from air into cornea is bent and the curved surface of cornea plays the major role in focusing. Changes in lens shape make adjustments (accommodation) for distance. Lens shape is controlled by zonular fibers that are in turn controlled by the smooth ciliary muscle. To focus on distant objects, the lens is pulled into a flattened oval shape. For near vision, the pull is removed to make the lens more spherical and provide additional bending for light rays. Cells of the lens lose their organelles and are therefore transparent. The lens become progressively opaque as newer cells replace older ones, which accumulate in the lens. This is called cataract. If the lens loses its elasticity (due to age) and cannot assume a spherical shape, it leads to loss of near vision and this is called presbyopia. If images of far objects focus at a point in front of retina, the eye is nearsighted or myopic and far vision is poor.

If images of near objects focus at a point behind retina, the eye is farsighted or hyperopic and near vision is poor. If the lens or cornea is not smooth, it is called astigmatism. The lens separates an anterior chamber filled with aqueous humor and a posterior chamber filled with vitreous humor. If aqueous humor is formed faster than it is removed, it results in an increased pressure within the eye. This can cause irreversible blindness with the death of optic nerves and it is called glaucoma. The pigmented, opaque iris that has a central hole, the pupil, controls amount of light entering the eye. The iris has smooth muscles, innervated by autonomic nerves. Stimulation of the sympathetic nerves dilates the pupil to let in mare light when light is poor and stimulation of the parasympathetic nerves constricts the pupil to allow in less light when light is bright. Photoreceptor Cells Rods - sensitive and responding to low light and cones - less sensitive and responding to bright light. There are three kinds of cones containing red-, green-, or blue sensitive pigment. Photoreceptors contain photopigments, which absorb light.

There are 4 photopigments, rhodopsin in the rods and one in each of the 3 cone types. Each photopigment contains an integral membrane protein, opsin, which binds a light sensitive chromatophore molecule. The chromatophore - retinal (a derivative of vitamin A) is the same in all the 4 photopigments. The opsin is different in each type of photopigment, absorbing light at different wavelengths of the spectrum. Light activates retinal, causing it to change shape and triggering a hyperpolarization in the bipolar cells, which synapse with the photoreceptor cells. After its activation, retinal changes back to its resting shape by light-independent mechanisms and the photoreceptor cell is depolarized Neural Pathways Photoreceptor cells synapse with neurons called bipolar cells which, in turn, synapse with ganglion cells that produce the first action potentials in the chain. Axons from ganglion cells form the optic nerve, which crosses over to the opposite side of the optic chiasm. Sound Transmission in the Ear Outer Ear (Pinna/Auricle) - Directs and amplifies sound waves.

External Auditory Canal –the ear canal leading from the outside to the middle ear cavity Tympanic membrane (Eardrum) - Vibrates at the frequency of sound waves. Middle Ear Cavity - Filled with air. Has a movable chain of 3 bones, the malleus, incus and stapes that couple and amplifies the vibrations in the tympanic membrane to the Oval window- a membrane covered opening separating the middle ear and the Inner Ear (cochlea) Scala vestibuli - Filled with fluid Cochlear duct - Lined by the basilar membrane upon which sits the organ of Corti containing the receptor cells. Organ of Corti Receptor cells of the organ of Corti, the hair cells, are mechanoreceptors that have hairlike stereocilia. Vibration of the basilar membrane, with which the hair cells are attached, stimulates the hair cells and the pressure waves are transformed into receptor potentials. Neural Pathways Afferent neurons from the hair cells form the cochlear nerve. Hearing Entire audible range extends from 20 to 20,000 Hz.

Vestibular System A series of fluid filled tubes in the inner ear that connect with each other and the cochlear duct containing hair cells that detect changes in motion 2 Parts: Detect angular acceleration during rotation of the head along the three axes. Utricle and Saccule Provide information about linear acceleration and changes in head position relative to gravity. Vestibular Information Information from hair cells in the vestibular apparatus is transmitted to the parietal lobe and is integrated with information from other parts of body, leading to sense of posture and movement. Unexpected inputs from the vestibular system leads to vertigo or motion sickness. Chemical Tastes Taste Taste buds found on the tongue respond to 4 basic modalities, sweet, sour, salty and bitter. Each groups has a distinct transductional system. Organized into independent pathways but a single receptor cell may respond to more than one taste category in various degrees. Smell Odor is related to chemical structure of a substance. Olfactory receptor cells lie in the olfactory epithelium in upper part of nasal cavity. These cells have several long, non-motile cilia, which contain binding sites for olfactory stimuli. Each cell contains one type of receptor.

Axons of olfactory receptor cells of same specificity synapse together. Information is passed into the olfactory cortex in the limbic system. Biology | Multiple Choice Quiz Multiple Choice Quiz Of the following processes, which occurs in dendrites? A) The taste that most people sense on the back of the tongue is A) sour 4 Whether a hair cell depolarizes or hyperpolarizes depends on whether it bends toward or away from A) In the cochlea, the hair cells are contained by the A) The amount of light entering the eye is determined by the size of the A) The cells responsible for color vision in vertebrates are called A) Which of the following substances is involved in the electromagnetic and chemical events of vision? A) Which of the following is not a mechanical stimulus? A) Nerve impulses are carried from the eye to the brain by the A) vestibular apparatus 11 The membrane that separates the outer ear from the middle ear of mammals is called the A) tympanic membrane 12 Which of the following is not one of the four taste classes that taste buds respond to? A) Rod cells and cone cells are located in the A) Which of the following sensory systems is not found in fish?

A) all of the above are found in fish 15 The simplest sensory receptors in a nervous system are A) free nerve endings that depolarize in response to direct physical stimulation C) mechanical receptors that employ a lever device D) auditory receptors 16 Which of the following sensory systems of vertebrates did not evolve first in an aquatic environment? A) The most sensitive vertebrate chemoreceptors known are the A) rod and cone cells of mammals B) organs of Corti of humans D) organs of Corti of bats 18 Compared with chemical stimuli, auditory stimuli A) The Eustachian tube connects the A) outer ear and middle ear B) middle ear and inner ear C) Which of the following sensory receptors function via hyperpolarization rather than depolarization? A) The fovea is part of the A) organ of Corti 22 Which of the following is not one of the ossicles in the middle ear of humans? A) Which of the following stimuli can be detected by a proprioceptor?

A) Information transmitted from the pit organs of a snake is processed by A) the auditory center of the snake's brain C) the visual center of the snake's brain E) Receptors that report your arm position and tension are: A) Which is a functional mismatch? A) Meissner's corpuscles -- detects light touch of the skin C) semicircular canals -- detects rotational movements in the three dimensions of space D) vestibular apparatus -- detects changes in speed or direction of movement 27 In which of the following animals would you expect to find the protein opsin? A) Which of the following statements is correct? A) In order to produce a clear image, the aqueous humor is involved in the process of accommodation. B) The space anterior to the lens is filled with the vitreous humor. C) The function of the crystalline lens is to bend light rays and focus them on the optic nerve. D) The amount of light entering your eye is regulated by smooth muscle in the ciliary body. E) Nearsightedness is a condition resulting from loss of lens elasticity. 29 Which of the following statements is incorrect?

A) The human eye contains both rhabdomeric receptors, the rods, and ciliary receptors, the cones. B) Rhabdomeres are found in the compound eyes of insects, but not in the eyes of octopi. C) In mammals, color vision depends upon three types of cones that are maximally sensitive to three different wavelengths of light. D) Suffering from a Vitamin A deficiency leads to night blindness. E) Accommodation involves the ability to change the width of the lens by contracting or relaxing certain muscles. 30 Muscle spindles are stretch receptors. A) Human Retinal Pigment Epithelium and Bruch’S - Choroid Membrane in vitro Organ Culture Working Model | IOVS | ARVO Journals ARVO Annual Meeting Abstract | May 2008 Human Retinal Pigment Epithelium and Bruch’S - Choroid Membrane in vitro Organ Culture Working Model Dept of Ophthalmology, King's College London, St Thomas' Hospit, London, United Kingdom Dept of Ophthalmology, Ruijin Hospital,, Shanghai Jiao Tong University, China J.

Zhang Dept of Ophthalmology, King's College London, St Thomas' Hospit, London, United Kingdom A. El-Osta Dept of Ophthalmology, King's College London, St Thomas' Hospit, London, United Kingdom A. Hussain Dept of Ophthalmology, King's College London, St Thomas' Hospit, London, United Kingdom P. Munro EM unit, Institute of Ophthalmology, London, United Kingdom J. Marshall Dept of Ophthalmology, King's College London, St Thomas' Hospit, London, United Kingdom Footnotes Commercial Relationships Y. Sun, None; J. Zhang, None; A. El-Osta, None; A. Hussain, None; P. Munro, None; J. Marshall, None. Footnotes You are adding an alert for: Human Retinal Pigment Epithelium and Bruch’S - Choroid Membrane in vitro Organ Culture Working Model You will receive an email whenever this article is corrected, updated, or cited in the literature. You can manage this and all other alerts in My Account The alert will be sent to: Get Citation Citation Y. Sun, J. Zhang, A.

El-Osta, A. Hussain, P. Munro, J. Marshall; Human Retinal Pigment Epithelium and Bruch’S - Choroid Membrane in vitro Organ Culture Working Model. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1757. Download citation file: © 2017 Association for Research in Vision and Ophthalmology. × Supplements Abstract Purpose: : The aim of the study is to establish a human retinal pigment epithelial (RPE) and Bruch’s -Choroids membrane (BCM) organ culture working model that more closely represents the in vivo environment. This will enable us to investigate the cellular and biochemical responses of the RPE-BCM system associated with laser or the other treatments. Methods: : Explants of human RPE still attached to BCM and sclera were prepared from donor eyes (12 to 72 hours post-mortem) and clamped in a tailor-made Ussing chamber to isolate the apical sides of the RPE from the choroids.

Freshly prepared explants were firstly covered by pure fetal calf serum (FCS) for overnight at 37 degrees C and then transfer to a organ culture system in Dulbecco’s modified Eagle’s medium (DMEM)/F12 nutrient supplemented with 15%FBS and bFGF for various periods up to 8 weeks.The morphology and functional behavior of the system were assessed by using phase-contrast microscopy, transmission electron microscopy and confocal immune-fluorescence. Cell viability and proliferation assays were also used to quantify RPE survival and division at different time points. Results: : The study shows a viable human RPE-BCM organ culture working model, which enables us to maintain RPE cells attached to the Bruch's membrane for up to 4 weeks without significant cell death and detachment. Majority of RPE cells showed Caicein AM positive staining in the examined explants and confirmed by MTT viability assay.For up to four weeks in the organ culture system the RPE cells remained as a monolayer and retained several prominent ultrastructural features, including apical microvillus, intracellular melanosomes and mitochondria.

The ability of this system to maintain it native barrier function was also confirmed by labelling the expression of the tight junction protein ZO-1. Conclusions: : These results suggest that the system is suitable for the short-term maintenance of RPE for experimental purposes. The ECM can exert crucial impacts on cell behavior and the ability to maintain RPE cells attached to the Bruch's membrane provides a new in vitro tool for studying the cellular and biochemical activity and its response to external stimuli, including laser treatment. Keywords: retinal pigment epithelium • extracellular matrix • cell survival © 2008, The Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Permission to republish any abstract or part of an abstract in any form must be obtained in writing from the ARVO Office prior to publication. 6 Views Analysis of retinal pigment epithelium integrin expression and adhesion to aged submacular human Bruch's membrane. - PubMed - NCBI Analysis of retinal pigment epithelium integrin expression and adhesion to aged submacular human Bruch's membrane.

Abstract PURPOSE: Uncultured aged retinal pigment epithelium (RPE) does not resurface aged Bruch's membrane after 24 hours in organ culture. These experiments assess whether culturing alters RPE integrin expression and resurfacing of Bruch's membrane. METHODS: RNA was isolated from uncultured and cultured RPE of aged adult donor and fetal eyes. Integrin subunit messenger RNA (mRNA) expression was studied by reverse transcriptase-polymerase chain reaction (RT-PCR) and semiquantitative analysis of the amplified products. Cell surface integrin expression was assessed using flow cytometry. Passaged cultured fetal RPE and primary cultured aged RPE were seeded onto Bruch's membrane, and resurfacing was assessed with scanning electron microscopy. RESULTS: Uncultured fetal RPE had low levels of alpha3 and beta5 mRNA compared to passaged cultured fetal RPE. Uncultured aged RPE had decreased alpha1-5 mRNA compared to primary cultured aged RPE. Cultured aged RPE had decreased beta4 and beta5 mRNA compared to passaged cultured fetal RPE.

Flow cytometry confirmed the expression of alpha1-5, alphav, and beta1 protein on cultured fetal RPE and alpha1-3 and beta1 protein on cultured aged RPE. Twenty-four hours after seeding, cultured fetal and aged RPE resurfaced 99% +/- 1.3% and 76% +/- 22%, respectively, of aged submacular Bruch's membrane specimens from which native RPE had been debrided, exposing the native RPE basement membrane. Cultured fetal and aged RPE resurfaced 97% +/- 3.1% and 39% +/- 35%, respectively, of specimens in which the inner collagenous layer was exposed. CONCLUSIONS: Uncultured aged RPE has low amounts of integrin subunits that form receptors for laminin, fibronectin, and collagens. Culturing up-regulates integrins and promotes more efficient aged RPE attachment to and survival on aged Bruch's membrane. PMID:

Question: In which human sensory organ is Bruch's membrane?
Answer: Eye