Hello again internet friends!
Today I’m going to be talking about the nervous system. I know it seems like such a big subject but I’m gonna try to go through everything I learned in two posts so I can get on with posting about all the systems before my exam in May. My brain is already in agony… But I know I can do it! So shall we begin?
When you think of the nervous system, what do you think of? Before I learnt anything about the nervous system I would’ve said the brain and nerves. I wouldn’t have been wrong but there is so much more to the nervous system than that! The nervous system is so incredibly complex but also incredibly fascinating and I’m going to try to teach you how it works from what I have learnt.
The nervous system’s main job is to receive information via our sensory receptors. It then has to quickly translate that information in the brain to immediately tell our bodies how to respond to the information that has been received. For example, if you touched a hot pan by accident, the touch receptors in your hands would send a message to your brain saying that the object you are holding is too hot to touch. Your brain would then translate that message and tell the muscles in your hands to immediately take your hand away from the hot object that is causing you pain. This is what I would say if I were to tell a 5-year old about the nervous system. But, since I am not 5-years old and because I’m guessing you aren’t either, let’s go more in-depth about the nervous system.
If you were to look at the nervous system in a big picture, it would be divided into two parts. The central nervous system (CNS) and the peripheral nervous system (PNS). The CNS comprises your brain and spinal cord, and the PNS are all the nerves that spread out from the CNS that aren’t part of the brain or the spinal cord. It’s kind of like the CNS being a tree trunk and the PNS being the roots or the branches that spread out from the trunk. Both have very important roles in the human body and we could not live without one or the other.
As you can see in this giant diagram above, the PNS has lots of subdivisions. The PNS controls the motor neurons and the sensory neurons, and it is the motor neurons that get divided into the somatic and autonomic division of the nervous system. The somatic division is where you have control over your movements and the autonomic division is where you don’t have control over your movements such as your stomach. You don’t think about digesting the foods you ate because the autonomic division does it for you. And in the autonomic division are the last two subdivisions, the sympathetic and the parasympathetic division. The sympathetic division comes to work when you are in the fight or flight mode. For example, if you were to be walking along a sidewalk on a sunny day and suddenly see a huge spider, you would immediately let out a few bad words and jump or run away from it. The parasympathetic division starts doing its job when you are in a relaxed state away from the danger of stepping on a spider, the rest and digest mode. It lets your body do the digestion it forgot to do while you were running away from that spider and also reminds you that you were on your way to go for a wee.
So now that I have gone through the different systems and the subdivisions of the nervous system, let’s dive in a bit more deep into the CNS.
As I mentioned earlier, the CNS consists of the brain and the spinal cord. It interprets sensory information being put in and also commands responses to the rest of the nervous system. It will command responses based on past experiences, reflexes, and current conditions.
Like for instance, if you get bitten by a dog, at that moment your reflexes tell you to take your hands away from the dog. When you see that dog again, your brain tells you not to go near it from your past experience. But now the dog is very calm, wagging its tail at you, wanting to be loved. Then your brain thinks “hmm, maybe it’s okay to pet the dog now”, so you’ll go over to the dog and start petting it. This is an example of how the CNS commands responses.
Moving on to the anatomy of the brain which is where most of the CNS does its job. As you can see above, the brain can be divided into 5 parts with 1 extra non-official part. The different parts consist of 4 different lobes and the cerebellum which actually looks a bit different from the rest of the brain. The 4 lobes are the frontal, parietal, temporal, and occipital lobe. Each lobe controls different functions such as the occipital lobe controlling the functions of vision and temporal lobe controlling functions for hearing and facial recognition. I won’t go through all the functions of the lobes since you can see them all in the diagram.
Now shall we talk a bit more about the PNS? But before we do, I’m going treat myself with some brain looking walnuts, to get me going.
Okie dokie, let’s move on the PNS. As mentioned earlier, the PNS consists of everything in the nervous system but the brain and the spinal cord. But what are they then? They are all the peripheral nerves, their ganglia(collection of nerve cell bodies), and sensory recpetors. Your sense of touch, taste, smell, hearing, and vision in your body? It’s all from the nerves that are a part of your PNS. I also mentioned earlier that the PNS gets divided into two subdivisions, the autonomic and somatic division in which the autonomic division gets divided again into the sympathetic and parasympathetic subdivisions. In the autonomic and somatic subdivisions, there are somatic fibers that supply nerves to the skeletal muscles, and autonomic fibers that supply nerves to the smooth & cardiac muscles and glands. I am wildly guessing that there are autonomic fibers in the muscles and glands for when we are in a fight or flight more or a rest and digest mode to control what our muscles do but I don’t recall going through the details of this in my lectures so I am going accept the fact as it is for now.
I think I am going to stop here before moving on to the cells in the nervous system. The nervous system was a big subject that I was scared to dive into at first so I understand if you feel the same way after reading this. But, I do hope that at least some of the information I explained was easy to understand. It’s challenging for me to try to teach a subject that I am not yet an expert in, but writing these blog posts are really helping me a lot so I aim to continue doing it! Till then!