In this video I describe the organization of the nervous system, which includes the central nervous system and the peripheral nervous system, which is then divided into the somatic and autonomic divisions. Next I discuss the sympathetic and parasympathetic systems which can activate responses in the autonomic division. I briefly explain how the fight or flight response can influence heart rate, breathing, sweating, digestion, and immune function, and how parasympathetic activation can help us to recover after a threat has passed.

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Video Transcript:

Hi, I’m Michael Corayer and this is Psych Exam Review and in this video I’m going to explain the structure of the nervous system.

So we can divide the nervous system into two main parts. First we have the central nervous system or the CNS. This is going to include the brain and the spinal cord. And we can see the importance of these structures because they are “armored” by that I mean they’re encased in bone to protect them. So we have the skull around the brain and then we have the vertebrae of the spine, I’ll try not to have too much scoliosis here, wrapping around the spinal cord to protect it. we have these bones of the vertebrae protecting the spinal cord and we have the skull protecting the brain.

Then we also have the peripheral nervous system or PNS. And the peripheral nervous system is everything else; all the other nerves and systems in your body are going to be part of the peripheral nervous system. So we’ve got all this other stuff here. A person here.

Ok, so all the other nerves in the body, so we have all these nerves coming off the spinal cord going to muscles, all sorts of digestive system stuff, organs in the body, these all have nerves connecting to them and so we’re going to have all sorts of other stuff happening here and this is gonna be the peripheral nervous system.

Now because the peripheral nervous system has so much other stuff we divide up into sections. We say Ok of all this other stuff, there’s some stuff that we have control over. That’s going to be the semantic division of the peripheral nervous system. So the somatic division is anything that is voluntary. So your skeletal muscles and the nerves that connect to them are going to be somatic division. You can voluntarily choose to move those muscles in a number of ways.

But there’s also stuff in here, in the peripheral nervous system, that you don’t have that control over and this is all going to fall under the autonomic division of the peripheral nervous system. So the autonomic is all of this involuntary stuff.

It turns out there’s quite a lot of this. You can think of any of the processes in your body that you don’t have control over are going to be part of this autonomic division of the peripheral nervous system. So what would that be? Well that would be things like your heart rate. You don’t have to consciously think about contracting muscles in order to make your heart beat. You don’t have to think about breathing, that’s an involuntary process. It just happens on its own. Now it’s true that you can influence you can use some voluntary systems, move some muscles, that will cause you to take a deep breath. But for the most part you don’t need to think about your breathing. You don’t have to control it as you’re walking down the street.

In here would also be something like sweating. So there’s going to be some systems involved in making you sweat when your body starts getting hot to try to cool it off and again you don’t have conscious control over this. You don’ think “I’m gonna need to start sweating soon because I’m reaching a certain temperature”. It just happens on its own. Another one would be digestion.

So you don’t have to think about “Ok, I just ate a hamburger, now I need to release these enzymes and do all these things in order to break this down”. Somehow your body just knows how to do this and it happens automatically, it’s part of this autonomic system. This amazing process of transmogrification, which is this piece of cow, somehow my body knows how to take that and turned into a piece of me.

Luckily I don’t have to consciously think about. Also included in this would be things related to your immune system. Again, if I have some bacteria invader or I have some pathogen I don’t need to consciously think about “Ok I need to release some white blood cells here in order to fight off this particular threat”. Instead my immune system just does this automatically.

Now all these systems of the autonomic division, your heart rate, your breathing, digestion, these are connected to one another by that I mean there’s certain patterns to how they work. They don’t occur in isolation. It’s not the case that your heart rate suddenly goes up and your breathing drops and you start sweating and then you start digesting a hamburger. There’s a pattern to how these things happen.

There’s two main ways that we can think about activation of these systems. So we’re going to have a further division here. So you can have two types of activation. We have sympathetic activation of the autonomic division, and what this refers to is facing threats. So this would be where the fight or flight response would be a great example of sympathetic activation.

So what happens when you face a threat? So you’re walking in the woods and suddenly you’re being chased by a predator. Well, what’s going to happen is your heart rate is going to increase, your breathing is going to increase, you’re going to start sweating and those ones you’re going to be pretty aware of. You might not be aware that your digestion is going to decrease, your immune function is going to decrease because right now you need to escape this predator and the energy that you’re going to get from that hamburger in your stomach, well, if you don’t escape the predator you’re not going to need that energy. Put that on hold for a while. Same thing with your immune system. “Ok I’m trying to recover from some injury and I’m also fighting off some bacteria” but for now that doesn’t matter. The most immediate thing now is escaping from this threat.

So sympathetic activation activates heart rate, breathing, sweating, these sorts of things and it decreases the activity of digestion, your immune system. You can see this when you face other threats. Hopefully you’re not running from predators on a daily basis but you probably have other things that have sympathetic activation.

So you’re nervous before an interview or you have to make a speech in front of a large crowd. Well what are the things that you’re going to experience? Your heart rate is going to increase, you can feel your heart pounding, you can feel your breathing is different. You’re going to start sweating, you’re going to wish that you could consciously stop sweating but it’s an involuntary process so you can’t really help it.

You’re going to feel butterflies in your stomach, that’s changes in your digestive system. Your mouth is going to get dry because salivation is going to be decreased. Again, your body is not expecting you to suddenly start eating in the middle of a threat. When you’re running from a tiger you don’t stop and have a snack. So just before you make a big speech, your mouth is going to go dry. Your immune system is going to be compromised. If you’ve been under lots of stress lately you might find that you get sick.

Because your immune system is compromised, it’s not fighting off threats as well because of this sympathetic activation. So that’s one way, one pattern of activation we can see of the autonomic system and it’s probably no surprise that the other pattern is the opposite. This is what we call parasympathetic activation.

So the parasympathetic activation is essentially the opposite process. It’s focused on recovery. After we’ve escaped from that tiger, now we need to heal the wounds that we’ve, you know, we’ve scraped our arm on some branches and we need to recover from those. We need to get some food and we need to digest it and get some energy. So we have recovery and relaxation. Heart rate’s going to decrease, breathing is going to decrease, sweating is going to decrease. Digestion is going to increase. Immune function is going to increase. On the other hand, essentially, allow us to recover so that next time we face a threat we’re better prepared.

Now I said we don’t have conscious control over these processes. That’s mostly true, but of course, we can choose certain behaviors, we can put ourselves in situations that are going to activate one of these two systems. So I can choose to put myself in more threatening situations and I’m going to have more sympathetic activation. On the other hand I can also choose to recover and relax. I can try to put myself in situations that are going to encourage parasympathetic activation. So if I decide to sit quietly that’s going to encourage parasympathetic activation. If I take up a practice like meditation, that’s going to improve this process of activating the parasympathetic system, parasympathetic activation of the peripheral nervous system.

So that’s the general structure of the nervous system. We have the central nervous system, brain and spinal cord, then the peripheral nervous system which is everything else, and that can be divided up into voluntary processes which are somatic, then we have involuntary processes which are part of the autonomic division and then the autonomic division can be activated either sympathetically, this fight or flight response or parasympathetically, with this relaxation and recovery response.

I hope this was helpful, if so please like the video and subscribe to the channel for more.

Thanks for watching!