Alright, so, you know a bit about the brain, now what I want to do in this lecture is, is show you the really interesting connection that the brain has with the rest of the body. Let's go right to it. Alright, so. In this image you see the brain and you see the spinal cord here. these parts of our bodies are what we refer to as the central nervous system. The central nervous system is the real decision making part of us. Of course most of the complex decisions are, are performed by the brain itself and we're going to spend a lot of time talking about that and the various parts of it, and the sorts of decisions those parts are responsible for, but even the spinal cord can control some things, specifically reflexes. You know when the doctor taps your knee and your leg kicks out. that reflexive action happens somewhere in the spinal cord and the brain really has nothing to do with it at all. So we kind of combine, it's kind of like we imagine the brain extending within your spinal cord. And all of this we call the central nervous system. what we're going to focus on in this lecture though is everything you see in blue on this slide. Don't worry about all the, all the words you see over here, all the specific terminology. I'm not going to be worried about that. But this is the system, it's called the peripheral nervous system. And it's the system that links the brain to the rest of the body. So specifically, especially to the muscles and to our internal organs. So really it is the connection the brain has to control the rest of the body. Now if we think about the peripheral nervous system in detail. and, and I'll demonstrate to you, this all to you by the end of this lecture. We can first of all kind of divide it into two parts. There's the somatic system. Now, the somatic system is the system that allows us to take intentional or voluntary control over our muscles and organs, and that, well, organs, well, some people, some people can do things like slow their heart rate and, and, and well, we all can to some extent but especially the muscles, really. Controlling the body through the muscles. the autonomic system, think of autonomic as kind of like automatic. This is a system that reacts predominantly to the stimuli in our environment and it kind of does one or two things. It puts our body into one of two different modes, and those modes are called the parasympathetic. And the sympathetic. So I'm using this light switch analogy here because to some extent that's kind of what the autonomic system is. It can flip our body from one mode to another. Okay, what am I talking about. Well, let's do it because I think this is kind of cool actually, when you get into it. Alright, so let's, let's do the following. Let's say you had a hard day at work. You come home you've had your dinner, you made your dinner, you did your dishes, and now it's relaxation time, so you sit on the couch, you relax, you watch some TV. let's call it couch potato mode well when you're in that sort of couch potato mode it's the sympathetic mode that kind of takes over in your body. And this sympathetic mode has the goal of keeping your body healthy and alive for the long-term. So, it will do things like this. First of all, it constricts the pupil. That's just a normal part of relaxation. But it stimulates salivation, so you get a little more saliva in your mouth. it in, it slows the heart, inhibit sounds a little strong here, but it slows your heart rate, it slows your breathing rate, and it stimulates a bunch of digestive processes. So, in a sense, what it's doing is, taking that food you just ate and it's. It's ratcheting up those processes that take the nutrients out of the food, and it delivers those nutrients to the, to the body. while separating out the waste, and disposing of the waste, you know. Filling the bladder and, and, basically, you know, getting rid of all of the waste in the food, so, kind of think of this like maintenance on your house. You know, every now and then the house gets a little dirty and you gotta pull out the vacuum cleaner and clean things up and, and, you know, get the house back to where it's supposed to be. That's kind of what the parasympathetic system is doing. When it's relaxation time. It's delivering nutrients to all of the muscles and getting rid of the waste. And that's perfectly fine unless there's something urgent. Okay, so specifically imagine you're sitting on that couch chilled out, relaxing but then suddenly you, you see out of the corner of your eye somebody run by your window. in your backyard, and they have a gun. Okay? And let's say you know that your doors are unlocked. and so suddenly you have an emergency on your hands. What happens to your, you know, nice little chilled-out state? Well, a bunch of things happen. First of all, your pupil will become larger, allowing more light in. That gives you a better view of what's around you. your mouth will become dry. That's a, that's part of the digestive system shutting down. In a sense your body's saying, you know what? Don't worry about all that nutrition stuff right now, we have a real problem. Your, lungs will relax, but what that really means is you'll start breathing harder. So you'll get more oxygen, your heart rate will beat faster. So you'll start taking that oxygen into your blood and delivering it to your muscles. Your digestive activity will shut down. you will have sugar released by the liver. Again sugar also provides strength and energy to the muscles and basically all of this stuff about getting rid of waste shuts down. So, it's, it's literally like, okay, forget about digestion, forget about all that long term survival thing, we have a short term survival issue. And so what the body is doing, is delivering this sugar and oxygen rich blood to all the muscles. And it's making you ready for action. You know, if you've every heard any of those stories about mothers that are able to pick up cars because their children are, are trapped underneath. That's the sympathetic nervous system. It gives you that strength. It gives you that energy. And it's automatic, okay? You don't have to sit on the couch and go, oh there's an intruder with a gun. Okay, lemme get myself kind of psyched up here. No. It doesn't happen that way. It goes bang. You suddenly feel it. All kicks in. You get up. You get ready. And, wh, what are you getting ready for, by the way? Well you are getting ready to either fight or to flee. Right? You have, and both of those require muscles. So if you're going to take on this intruder, you need the strength to take them on. if you're going to choose to get the heck out of there, then you need the strength to get the heck out of there, and that's what the body's all about in sympathetic moment. It's about short term survival. So really fascinating, we have like I say, this switch where we can go almost instantaneously from relaxed to energized. It's not quite as instantaneous going back. that takes a little while longer, perhaps as you slowly go into a more relaxed state. So, I don't really want to imply these are like two sides of a coin, they're more like two ends of a continuum, but you can get from one end to the other pretty quickly. The cool thing is, that it's sort of every things the opposite in these two modes. all of these things we're pointing out move in opposite directions. Digestion slowing down, activation, you know, speeding up, et cetera, et cetera. alright so you've got that. let me actually go backwards for a second here. So we did the autonomic nervous system and you got the sense that there's this switch. But that's not the whole story. There's the somatic system that can also play a role. It can only play a limited role in some cases, but it can play a role. So let me give you an example of that now. So here we, here we have a nice beautiful casserole. So let me give you a story to put this in context. Let's say I have been invited to a potluck dinner with my friends. I am a vegetarian, and so I see this as an opportunity. This is an opportunity to show my meat eating friends, that in fact vegetarian food can be pretty good. it can be really good. [LAUGH] Did I just say, pretty good. Alright so, let's say I spend all day working really hard cooking this beautiful vegetarian casserole that you see right here. You know, maybe a nice spicy black bean casserole. and it's in the oven, it's just about ready, it's time to take it out of the oven. That's the setup okay, so now let me, let me actually switch to the other camera and act something out for you. Alright so here we go I may kind of come in and out of the camera a little bit. Where did my casserole go, I had a casserole here oh yes, I forgot, I, I made it like those TV shows. This is my cassarole. Okay? So I'm going to put my casserole in the oven right now. And let's say, hm, how am I going to do this? Okay. Let's say I, I put my oven mitts on because it's hot. But I forget that this oven mitt has a hole in it. Okay? So I forget all about that. I reach into the, the oven, and I am now bringing the casserole. Now at this point my, that hole starts to allow the heat in, and I'm starting to feel intense pain. Okay, that kicks in my sympathetic nervous system. I'm like, so all those things we talked about are kicking into gear. but as that happens what, what my sympathetic nervous system will start doing is sending signals to my muscles to say let go. So let's say they send an excitatory signal to certain muscle groups that would, if that was all that was going on, open my hands and drop my casserole. But wait, I don't want to drop that casserole. I spent all day, this casserole means a lot to me. So at that point, that's when my somatic system kicks in. And it might do the following, it might from my brain send a signal to those same muscles but inhibitory ones, so it will fight the signal that's being sent by the autonomic nervous system. And it will say, oh no you don't. Don't drop that. Hold on to it. And it might at the same time send an excitatory signal to my leg. And it would say, no hold onto it, get your butt over to that table as quick as you can, and so you see this sort of look. But while the person's doing that, they bring it somewhere, drop it, and they go ahhh, [NOISE]. And they take care of their hand, okay? Alright. A little silly, perhaps. But that moment, where you have those two signals let's. let's go back to the other slide now. Alright. So that moment, where you have the sympathetic nervous system sending an excitatory signal to the muscles, but then the somatic system counters that. Okay? And literally now, we have a bit of a fight going on. The somatic system can only keep up that fight so long. Okay? The, the sympathetic nervous system will win. But if it keeps it up long enough, and especially if it sends activation to the leg muscles to get you to a place where you can put that down, then everything works out, okay? So that example and you've probably been in that situation yourself. That gives you a really good sense of this peripheral nervous system and how it all plays out in terms of the brain trying to control the body. Okay. So, I hope that was kind of fun for you. it's fun for me. I'm still breathing there. Okay. I've got some some more things for you to follow up. There's a video that kind of brings you through the nervous system in a little bit more detail. so you can check that out. I threw in a, a nice recipe for a spicy black bean casserole. Just in case I made you hungry and you wanted to try out some vegetarian cuisine. I also have a reading for you about the nervous system and a nice active learning experience. So this is a website where you can learn a little more about the nervous system and take quizzes. Really good active learning, so I encourage you to try that out as well. Alrighty, so, that's the, peripheral nervous system, so we have the brain, we have the peripheral nervous system. let's take it from there.
