Hey folks, Dr. Ner here and in this video we'll be talking about soatic autonomic motor pathways or just autonomic pathways. Uh in this part we're really going be focusing on the motor pathways of autonomic nervous system less so on the sensory ones because well they're a little more straightforward. So purge is going to focus on these ones since we can draw some really big differences between the somatic and autonomic nervous system based off their motor pathways aside rather than their sensory pathways. So uh just to recap for the somatic nervous system uh right when we talk about their somatic motor pathways you know we're talking about a pathway that starts somewhere in the central nervous system typically in the cerebral cortex travels through the cerebral uh through the central nervous system so brain and spinal cord and then eventually leaves out to an aector organ. And so for the factor organs for the somatic nervous system were exclusively skeletal muscles. So that's what we're showing here skeletal muscles. So we had somatic motor neurons go from the central nervous system all the way to these skeletal muscles. That was it right? Sure. Now that the path was very complicated, right? It had to go to spinal nerves and plexuses and the peripheral nerves and yada yada yada. But that's you know if we take away all that detail that's basically it is it's just basically a sematic motor neuron going from the central nervous system to some skeletal muscles. That's what sematic motor pathways are about essentially for the autonomic nervous system there. Well first of all remember we have two two divisions parasympathetic and sympathetic. And so they both look slightly different which we'll get into in a moment between the two but there's a lot of commonalities and a lot of things to contrast these autonomic motor pathways to the sematic motor pathway. So first of all the aector organs are very different. So instead of going to skeletal muscles autonomic motor pathways go to other aector organs. They go to the heart, the heart. They go to glands like sweat glands and other kind types of glands like adrenal glands. They go to smooth muscle, blood vessels and atipose connective tissue. So they go to a bunch of different types of organs. And the general gist of is it is if the nervous system controls certain organs uh as a facector organs and we don't consciously have any control over it then it is automatically part of the autonomic nervous system and so this is just kind of a broad categorization of it right but this is the gist of it right it's going to heart glands smooth muscle blood vessels atapost connective tissue but you might say Dr. In the previous video, we said it went to the digestive tract. It went to um the lungs and that is true technically, but specifically within the lungs and within the digestive tract, it's going to what? Smooth muscles and smooth muscle tissue and blood vessels. So that's why and and glands. So this is a little bit of a um more generalized way of kind of thinking about the different types of aector organs we can have in the autonomic nervous system. Couple other differences here. So the autonomic nervous system instead of having one neuron that leaves the central nervous system and go goes to the affectctor organ. So basically all of this is encompassed in the peripheral nervous system. So in the somatic nervous system we had basically just one neuron that travels through the peripheral nervous system to get to its affectctor organ. In the autonomic nervous system whether it's parasympathetic or sympathetic we have two neurons that are linked by a synapse here that travel through the peripheral nervous system to get to these aector organs. Now this is where you can start seeing the differences. The parasympathetic nervous system that first neuron is longer but the sympathetic nervous system that second neuron is longer. All right, we have names for these neurons. And here we have the first neuron we call the pre gangleionic neuron. The second one we call the post gang neuron. And it's because these two neurons synapse at a ganglen. So hopefully you remember what gangalene is from a couple topics ago, but that's what's these names are. We're not going to really use these names a whole bunch in these videos, but I'm putting it out there just so you know. So again uh the affectctor organs for autonomic nervous system is the heart gland, smooth muscle, blood vessels and atapose tissue here and we have at different nervous system and then we have these two neurons and theories that make up the motor pathway at least went into the peripheral nervous system. Okay, so here you have a picture of the nervous system and we just have basically a bunch of these motor pathways leaving the central nervous system and going to all these different affect organs, right? And so on the left hand side here we have all the parasympathetic responses and all the right hand side we have the sympathetic responses and we can see the pathways that uh for the sympathy pathway in green and for the parasympathetic is blue and already we can see we're going to kind of ignore like the stimulatory inhibitory effects. Ignore that for now. But we'll see that at least where these pathways start is generally grouped right. So for the parasympic pathways they usually start somewhere in the brain in the cranial region or somewhere in the sacral region. And then for the sympathetic nervous system um they start somewhere in the thoracic or lumbar region here. Right? So we have this very clear kind of separation about where these motor pathways start at least when we talk about the peripheral nervous system portions right sometimes because that we call the parasympathetic nervous system the cranio sacral division of the autonomic nervous system and sometimes we call the sympathetic nervous system the thoracic the thoraso lumbar division of the autonomic nervous system. You don't need to know these names, but you do need to know that kind of where these kind of pathways will start within the central nervous system. That's kind of important because as we'll talk about very soon, right? All these pathways start in the in the brain here. What do they be? What nerves are they traveling through? They're traveling through cranial nerves because again, these are pathways coming straight out of the brain. So they're going to be using cranial nerves while the rest of it here are going to be using yes spinal nerves. True. But these pathways will look quite different than these pathways for example. So let's get into it. I said that already. All right. Let's talk about parasympic pathways here. So like I said a lot of them all the parasympic pathways come either from straight out of the brain here or part of the sacral region here. We're going to ignore the sacral region because there's to be honest there's not a bunch of pathways that are really happening from here, right? They'll start from the sacral part of the spinal cord and they go to different parts typically found in the low lower abdomen. So the genitals um sex organs like uh the uterus or testes or something like that bladder parts of the rectum those kind of parts parts of the pelvis here. So all the other pathways for the all the parasympathic pathways for the rest of the body really start here somewhere by the brain stem here, right? And you can see that we can have pathways that go from the brain stem to go parts of the face, right? The eyes and the tear glands and whatnot. But we can have pathways that start from the brain stem and travel all the way down into the torso. They go to liver, stomach, lungs, pancreas, heart, you name it, right? And these pathways are still being used. They're traveling through cranial nerves because again there they're starting by the brain stem. They're going to be using cranial nerves. So a lot of these parasympathetic pathways are um being conducted by cranial nerves specifically cranial nerve number three, 7, 9, and 10. These are Roman numerals. I'll say it again. 3 7 9 and 10 here. And the big one we really want to think about is this one number 10. So if we zoom into this picture, we can see like here's three, seven, nine, and 10. So like three kind of goes to the eye. That's nice. Seven can go to like the nose and like the tear glands here. Nine is going to some uh salvary glands here. Right. Great. Um but nine nine goes to some very very important organ. Sorry 10 10 which is known as the vagus nerve here goes to some very important organs. that goes to the heart, the lungs, the liver. And so this nerve here, the vagus nerve, cranial nerve number 10 here, really conducts a lot of motor pathways or the parasympic responses for very important organs here. In fact, 75% of all parasympathetic commands and information, yes, a lot of these nerves are mixed. So they're taking sensory information from these organs as well and sending it to the brain is conducted by this nerve the vagus nerve pan nerve number 10. That's why we say the vagus nerve is really really important for the parasympic nervous system. It's because conducting so much of that information and the commands that are needed to kind of kind of create these parasympic responses. The sympathetic pathways work quite differently as this as as we saw most of the parasympic responses did rely on cranial nerves. Most of the sympathetic actually all the sympathetic nervous system sympathetic pathways here rely on the spinal cord. So information will travel from the brain down the spinal cord and then leave the spinal cord via spinal nerves very similar to uh somatic motor pathway. However, there's one big difference here and it relates to this big structure here that's found on either side of the spinal cord. So here we have the spinal cord. Coming out of spinal cord we have our spinal nerves here, right? And then kind of found kind of sitting parallel and to the sides of the spinal cord and the spinal nerves here is this kind of big trunk here. We find this on both sides. You just can't see the other side here. And this whole trunk here is called the sympathetic trunk. And each kind of bulge within the trunk here is called the sympathetic trunk ganglia. So that's gray matter in these kind of bulges here. And the sympathetic trunk here is really important because a lot of the sympathetic motor pathways will use it to kind of travel around the body. So here's an example, right? Let's pretend we have our spinal cord right here. This is our spinal cord. We have the motor pathway traveling down our spinal cord. It synapses here to our new neuron here. And this motor neuron will leave the spinal cord, go through some spinal nerves here. And instead of going through plexuses or peripheral nerves, whatever we learned in the somatic nervous system, it instead will use a sympathetic trunk. You can see like it goes here to a spinal nerve, then turns, enters the spinal cord and it may go up, it may go down. It depends where it needs to go. In this example, it can go up to a ganglion synapse with that second neuron which we call remember the um post gangic neuron. And that neuron will travel out here and then travel to whatever affectctor organ it goes to. So sympathetic trunk here is very useful for the synapses we find between our two neurons in our motor pathway here. And so this part is is exclusively used by the sympathetic nervous system. Hence we call that the sympathetic trunk here. And so those are kind of the structures and the pathways we see when it comes to sympathetic nervous system and the parasympic nervous system. In the next couple videos, we'll kind of put this all together to see how the autonomic nervous system works to kind of control the body, how it uses these affected organs given various stimuli and whatnot. Uh it's going to feel very much like reflexes. So get ready for that. I'll see you in the next video. Bye.