Introducing: The Nervous System.
By: Sam Bevan
Tags: Brain, Teaching And Learning, Nervous System, Medicine, Neuroscience

By Sam Bevan

We all want power. We all want money. We all want fame. And, we all want love. Let me tell you about someone who has it all. Well, it’s not a someone exactly, more of a something. And it kind of lives inside us. I know, a bit complicated. So, how about an introduction? Ladies and gentlemen (and puppies and aliens and rocks and whomever else is reading this article), let me introduce you to the Nervous System.

You want power? It’s got power. It controls everyone in the world. If you have it, it owns you. No further discussion. It’s got money, takes up 20% of your energy currency, you better pay up. It’s got fame, everyone knows that the brain is the sexiest organ in the body! And, it’s got love. Listen up, people, the heart is a phony. If you want the love, the brain’s got the oxytocin, also known as Love PotionTM. And the only reason you’re even reading this is because, ladies and gentlemen, you’ve got a nervous system. Right now, your eyes are seeing this, it’s converted into electrical signals, your optic nerve is picking it up, the impulses are buzzing down the electric wire to the brain where the centre’s for language and writing are lighting up and then telling your thinking centre to think that your mind is being blown, which I’m sure is what is happening right now. And all this, in a fraction of a second.

Can you believe it? Right now, my brain is admiring itself and all it’s other counterparts, how narcissistic and how absolutely, fudging, brilliant!

Hello. I’m Sam and I’m a medical student. Every day, as a medical student I learn spectacular things about the human body but my dog is not very interested in hearing about it. So, I thought, that perhaps, strangers on the internet might be. I’m not a real teacher but I’ve got quite a lot of things stuck in my head and I’d like to get it out once in a while. If you learn from my incessant rambling, great! If not, at least you’ll be entertained? (I hope).

Okay, so let’s jump right into it without further ado. Nervous System 101. Let’s get our brains to learn about how they learn.

Remember how I told you that the nervous system was the most powerful? Let’s consider the nervous system to be royalty and the Brain is the Supreme Queen. Obviously, as Game of Thrones has taught us, every Queen deserves a Missandei and a Hand. The Hand of the Queen is the Spinal Cord. It carries out the Queen’s orders and occasionally advices it. The neurons, however, are Missandei-s. They announce all of the Queen’s whims and fancies and translate to her, what the people, i.e., the cells, want. The Queen’s consort is the Endocrine System. It’s also responsible for control and coordinate but it’s waaaay slower and doesn’t know anything, just like Jon Snow.

The brain is divided into two parts: Central Nervous System and Peripheral Nervous System. The Central Nervous System (Also known as CNS, by its friends), consists of the brain and spinal cord while The Peripheral Nervous System consists of the nerves.

Central Nervous System

Let’s begin our discussion with the Queen B herself: No, not Beyoncé, Beyoncé’s brain. Well, everyone’s brain, human, that is (if any puppies, aliens or rocks are reading this, I’m sorry but I’m mainly going to be discussing human stuff since I’m a human, myself, and I’m learning about human bodies, sorry, please don’t hate me. Also, rocks don’t have nervous systems). The Central Nervous System includes the Queen and her loyal Hand, the Spinal Cord. It is guarded by a very, very strong army called the Unsullied, sorry, I meant Cranium. The Cranium or the Brain Box or as it is known by all, the Thick Skull, keeps the soft, mushy brain safe. The brain is made up of neurons, the fundamental units of the nervous system and their cheer leaders, I.e., the neuroglia. The spinal cord is a continuation of the brain tissue, it is literally attached to the brain like a hand (get it? Get it? *wink* okay, I’ll show myself out). The spinal cord has an army on its own, of course, it’s called the vertebral column. There is an opening in the skull called the Foramen Magnum (which literally means big hole in Latin) and the spinal cord exits through it to continue in the vertebral column.

Structurally, the central nervous system is made of two layers: the grey matter and the white matter. I know what you’re all wondering: is the grey matter actually grey and is the white matter actually white? My dear fellows, I’m pleased to tell you that grey matter is, in fact, grey, it’s actually pinkish grey, but we can ignore that, and white matter is also, in fact, white.

Grey matter is made of the bodies of the nerve cells while white matter is made of their tails. Fun fact, the nerve tails, also known as fibres, are insulated with fat called myelin to ensure we don’t get an electric shock from the inside, just like electric wires which are insulated with rubber (I think) to protect us from getting an electric shock from the outside. Myelin is white and hence, so is white matter.

In the brain, grey matter is on the outside and white matter is on the inside. And in the spinal cord, white matter is on the outside and grey matter is on the inside. You can remember it like this: the brain is round like a coconut, brown on the outside and white on the inside. Wait, never mind, the brain isn’t round neither is grey matter brown. Wait, let me try again, the brain is like Christian Grey, it’s called Grey but it’s actually white. Wait, never mind, that doesn’t make sense either. In case you haven’t noticed, I’m not very good at mnemonics. You can remember it however you like, just remember one and reverse the other.

The brain is covered by three layers, because it didn’t have enough protection already, obviously, haha. The three meninges, are the personal body guards who love the brain so much, they are literally like it’s mothers: Dura mater, Arachnoid mater and Pia mater from outside to inside (PAD from inside to outside). They’re called Mater because they really matter, alright? Also, they are made up of matter like everything else on this side of the Universe. Most importantly, Mater means ‘Mother’ in Latin. So basically, the brain has three over-protective mothers, I cant even handlr one. Dura mater means ‘thick mother’ because it’s very thicc. Okay, I’ll stop. Arachnoid mater means ‘spider mother’, it’s because the Arachnoid Mater is gangly and delicate like a spider web and Pia Mater means ‘tender mother’ because it’s the thinnest layer.

Between the Pia Mater and the Arachnoid Mater, is the subarachnoid space which is filled with cerebrospinal fluid. The Cerebrospinal Fluid (CSF) is a clear liquid that protects the brain and spinal cord by shock absorption and lubrication. The brain and spinal cord are suspended in this liquid.

Parts of the Brain

The Brain is broadly divided into three parts: Prosencephalon, Mesencephalon and Rhombencephalon. Also known as the forebrain, midbrain and hindbrain. The Forebrain is further divided into the Telencephalon and the Diencephalon. The telencephalon contains the cerebral hemispheres, basal ganglia, the hippocampus and the amygdala, so basically everything that helps you emote and then there’s the diencephalon which is made of the hypothalamus, thalamus, metathalamus and subthalamus. So, basically everything that’s called thalamus in the brain. Also, top to bottom, hypo means above, meta is middle and sub is below, so you can kind of remember this in order. The Rhombencephalon is again divided into the metencephalon and the myelencephalon. The metencephalon contains the Pons and the Cerebellum while the Myelencephalon is the Medulla Oblongata. It’s okay if you don’t know what all these words mean, I don’t either, yet, that is. I’ll explain it to you when I learn it in class. Also, fun fact, the midbrain, Pons and Medulla together are called the Brainstem.

Peripheral Nervous System

Now that we’re done overviewing Queen B, let’s take a look at Missandei, her loyal messenger: The Peripheral Nervous System. The Peripheral Nervous System or PNS is formed by the neurons. It is made up of two types of nerves: the cranial nerves, the ones that send and receive direct messages from Queen B and the Spinal Nerves which report the Spinal Cord. The PNS is divided into two types of systems: the somatic nervous system and the autonomic nervous system.

You have control over certain things. Like walking. Or reading this (thanks for choosing to do that, by the way) and you definitely don’t have control over certain things, like breathing, because, honestly imagine if you had to remember to voluntarily breathe. I don’t know about you but I’d definitely dead by now. The somatic nervous system controls things that you have control over, which are voluntary actions and the autonomic nervous system controls stuff you definitely don’t have control over, which are involuntary actions. So, basically, free will doesn’t exist.

The Somatic nervous system supplies the skeletal muscles which are voluntary. They help you walk and run and pick up things, etc. whereas the autonomic nervous system supplies the smooth muscles which are involuntary. They regulate the visceral functions. Our internal organs are called viscera and we don’t voluntarily control them because if we did, we’d be dead. They do stuff like digestion and respiration and detoxification which is basically what keeps us alive. If you want to take a moment to thank the viscera, go ahead. I’ll wait.

The autonomic nervous system also has one more very important function, as if it wasn’t doing enough already: keeping you safe. It is divided into two systems: the sympathetic and the parasympathetic. The sympathetic nervous system scares you and the parasympathetic nervous system calms you down.

It’s a bright, sunny day, and you’re traipsing down the road, singing songs and skipping along, like a normal person, and suddenly a snake appears out of nowhere, like a poisonous, King Cobra- Anaconda hybrid. Suddenly, the sympathetic nervous system takes over your body. A flash flood of hormones boosts your alertness and heart rate, sending extra blood to the muscles. You start breathing quickly which ensures more oxygen to the brain, so you can be alert; and to the muscles so you can start running, or fighting, though it’s not very advisable to fight a snake, unless you’re a mongoose. A dose of glucose is shot into the bloodstream for a quick energy boost. This response occurs so quickly that you won’t even realise that it’s taking place. And then, you run away from the snake and get to class. The professor starts droning on about something. You’re now out of danger and listening to the professor’s lullaby. Now, the parasympathetic nervous system takes over. It calms you down. It encourages to body to rest and digest. Blood pressure, breathing rate and hormone flow return to normal levels as the body settles into homeostasis, or equilibrium, once more. And you go to sleep. See, this is why you’re alive.

To conclude, while we are slaves of our respective nervous system, they are the reason we are alive. So, let’s all be grateful that we have them and use them wisely. I hope you enjoyed the introduction the nervous system. Thank you for coming to my TED talk.

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