Overview of Sympathetic Nervous System

Hi Ninja Nerds! In this video we're going to talk about the sympathetic nervous system. If you guys haven't already, please go watch the video on the introduction to the autonomic nervous system. We discuss a little bit of a little brief introduction into talking about the different types of ganglia and a little bit on the sympathetic nervous system and the parasympathetic. In this video we're going to go into a little bit more detail on the actual specific splanchnic nerves, right? And their target organs and then the functions of those target organs, okay? Before we do that though, I want to talk about this thoracolumbar outflow. Alright, so let's go ahead and talk about that first. So, if you remember, we talked about this in the autonomic intro video, that from T1 to L2, and again, take a little bit of grain of salt, there's some variance in there, sometimes it can be to L3. This is called the thoracolumbar outflow. It's a sympathetic outflow. Now, where are these, what are these blue things? These blue things, if you remember, are the cell bodies of the preganglionic motor neurons which are located in the intermedial lateral column or the lateral gray horn. I think that one's easier to say, but either way remember that you can find these blue guys here. These are the cell bodies of the preganglionic motor neurons of the sympathetic nervous system found in the lateral gray horn or the intermedial lateral column. All right, now what we're going to do is I want to talk about the outflow to these target organs. So we have these things on the side here, right? These are called your ganglia. What is a ganglia? A ganglia is just a group of cell bodies in the peripheral nervous system, which is outside the CNS, which is made up of the brain and the spinal cord, right? So outside of the brain and the spinal cord, you have these groups of cell bodies. They're called ganglia. If they're located on the side, they're called chain ganglia. If they're located in front, remember they were called pre-vertebral or pre-aortic or sub-diaphragmatic or collateral. A whole bunch of darn names for the same thing, right? What we're going to talk about in a lot of this video is the collateral ganglions. Okay, which we're going to stick with collateral or prevertebral, right? But I want to talk about these chain ganglia first, these top ones. This one right here, if you come up, an extension up here, these chain ganglia up to the cervical region, right around like C2 about, this is actually you're going to have what's called your superior cervical ganglia, which we're going to put SCG. You'll have another one at this level, which is the middle cervical ganglion. MCG or the inferior cervical ganglion which is the ICG but again there are some variants in different people sometimes the inferior cervical ganglion is fused with T1 they call it the stellate ganglion not necessarily super important but again wanted you guys to understand the variants here what I want to do is I want to talk about the preganglionic flow to the superior cervical ganglion and then out okay via to the head and neck structures that's we're going to start with first so first things first Generally, from anywhere from about T1 to T3, okay, about T1 to T3, these guys can come out, right? So here's what I'm going to do. I'm going to bring this guy in here. It's not going to synapse in that chain ganglia. It's going to move upwards, and it can synapse on the cell bodies in the superior cervical ganglion. And again, this can come from T1. It can come from T2. Or it could even come from T3. Alright? When these fibers move up, they can move up through the inferior cervical, middle cervical, up to the superior cervical ganglion. And synapse in the cell bodies here. From this point, they can then come out. When they come out, guess what these guys do? You know there's a big artery, right? There's a big artery here. You know, your heart, you have the common carotid artery. The common carotid artery actually bifurcates into the external carotid artery and the internal carotid artery. What happens is you can have this nerve fiber kind of swirl around the internal carotid artery and when it does that it forms a special plexus. We call this the carotid plexus. And it can actually come off and go to different portions around the head and the neck. The main ones we're going to talk about is going to be first the eye. Okay, so it's going to supply a lot of different structures here. Okay, the first one that we're going to talk about here is going to be the eye, right? Now, if you remember, those are the preganglionic, the blue. The black are the postganglionics. They release norepinephrine. There's only one exception to it, and we'll talk about that. And it's going to be the sweat glands. But here, what's going to happen is this guy's going to release norepinephrine. Now, what area is it going to act on in the eye? You know what there is? Around the iris. You have a specific muscle there. We talked about in the actual special senses videos. There's the Iris right has what's called the dilator pupillae right and think about these things logically in a sympathetic situation your fight your flight your fright situations what are you gonna want to do let's pretend that I don't know Chuck Liddell he's getting ready to come at you he's chasing you what's gonna happen well you want to be able to see all different types of options right so what would your pupils want to do in that situation would you want to only see things like very small amount of areas or would you want to be able to see a lot of stuff you want to see a lot of stuff So what's going to happen is it's going to release norepinephrine on this muscle here called the dilator pupillae. So what can it do? It can act on what's called the dilator pupillae. And when it acts on the dilator pupillae, it causes pupillary dilation. If it acts on the dilator pupillae and causes pupillary dilation, what does that allow for? That allows primarily for far vision. allows more light to come in. You're going to have a little bit more exception for the far vision. What else? It's also going to act on a muscle right here around the ciliary body. They call it the ciliary muscle. So it's also going to act on the ciliary muscle called the ciliaris. When that contracts, what it does is, is it actually helps the lens to become more flattened. When the lens becomes more flattened, it helps us to be able to see very, very far too. It's called accommodation. So the ciliaris allows for what's called accommodation and this accommodation can lead to the assistance in far vision right that's important then it's also gonna act in that remember I said the head and neck region we had a lot of glands in this area you know we have the salivary glands like the submandibular the sublingual the parotid salivary glands right and even other glands too associated with this but These are your main salivary glands, right? So the main thing is going to be your salivary glands. Let's put here salivary glands. And again, remember submandibular, sublingual, parotid. What's going to happen is they're going to release chemicals like norepinephrine, which can act in two places. One is that norepinephrine, remember this was norepinephrine, which is acting here. It can also release norepinephrine, which can act on two places. One is it could act directly on the blood vessel. It can act on the tunica media. You know there's the tunica media, the smooth muscle within the vessel wall, which constricts. When it constricts, it decreases the blood flow to the salivary glands, which decreases the actual substances that you can take for these salivary glands to take from the blood and put into the saliva. That's one important thing. The next thing is it also is going to act on the salivary glands directly. There's different types of adrenergic receptors. We'll have another video on that. When it acts on the salivary glands, it actually causes them to switch their mucus production. into producing more mucin, which is a glycoprotein which helps to thicken the mucus. So it's going to cause two different effects. One, it's going to cause a thick, viscous, thick, and viscous mucus production. Okay, so it's going to cause a thick, viscous mucus production. Alright, now, what about other glands? There's other glands besides salivary glands in this area. You know there's another one? Lacrimation. Right? So you also have what's called these lacrimal glands. So the other ones here called lacrimal glands. Now your lacrimal glands, what happens is norepinephrine can also act on the blood vessels in this area, constrict them, decrease the blood flow through the area, which decrease the lacrimation. Or it could act directly on the lacrimal glands and decrease lacrimation, right? So it's going to try to decrease lacrimation. Okay, so that pretty much covers this. Now what was this thing here called which comes off the superior cervical ganglion? They pretty much call this the carotid plexus. Okay, all right that covers that part. Now the next thing here is really important. Now there's other things that can come from the superior cervical ganglion and actually can join on to some of the actual spinal nerves and if it joins with some of the spinal nerves it can go to supply your Erectropeli. It can go to supply the actual blood vessels, the vasomotor supply, or it can also do what? If you remember, it can also code to the pseudoriferous sweat glands, okay, which are going to be important for pseudomotor control, which is sweat production. All right, but let's talk about these other ones here. So now we're going to have the middle cervical ganglion and the inferior cervical ganglion. These can give off branches too, but the most important branches for these guys are going to be Specifically, structures that are going to the heart, the lungs, and the esophagus. Okay? So they're going to give off fibers here, and these fibers here are going to be the We're going to go specifically to the heart, the lungs, and the esophagus. Okay, now another thing is the superior cervical ganglion can also give off some fibers too. It can also give off. So sometimes we call this the superior middle inferior cardiac nerve or plexus, right? And these are your sympathetic fibers. And what they're doing is they're going to three different targets. And what are these targets? One is it can go to the heart. If it goes to the heart, it acts mainly on two different areas. One is your nodal cells. Your nodal cells are important for heart rate. So what it's going to do is it's going to try to increase the heart rate. It's going to try to cause positive chronotropic action. So what's the overall effect here? It's going to try to, let's do a different color, let's say it increases heart rate. So one thing is it's going to increase heart rate. They call that positive chronotropic action, right? Another thing is it can act on the myocardium, the contractile muscle cells. If that happens, it can increase the contraction power. If that does that, if we increase contractility, we increase what's called cardiac output. And if you increase cardiac output, eventually that could increase your blood pressure. Okay, so that's a pretty cool thing there, right? All right, what else? It can act in the esophagus. Now... Generally, you don't, whenever you're in a flight or flight situation, or you don't want to be able to worry about digesting food, no. You don't really care about that. So it's going to try to decrease peristalsis of the esophagus. So for the esophagus, it's going to decrease peristalsis of the esophagus and certain secretions of the esophagus within the serum mucus. You have certain types of glands within this area, the esophageal glands. Okay, the lungs, the respiratory system, the specific... area that is affecting though is the bronchi. You know the bronchial smooth muscle? There's bronchial smooth muscle here that actually control the diameter of the airway. They control the airway resistance. So if the sympathetic nervous system is gonna act here, think about that. What are you gonna do if Chuck Liddell is coming at me, one of the toughest UFC fighters in history, right? What's gonna happen? I'm gonna, I'm gonna hyperventilate. I'm gonna get really scared. So you're gonna want to be able to allow for the dilation of the respiratory bronchioles. Because you're gonna want to be able to run away, right? Have as much air getting into your your blood as possible, as much oxygen, because you want to run away from that guy. Right, so what's going to happen here? It's going to dilate the bronchioles. So it's going to cause dilation of the bronchioles. Now another thing it can do, remember that it actually does have the ability to go to the vascular smooth muscle, I'm sorry, the vascular smooth muscle within the blood vessels in this area. Now why that's important is, is you don't want your blood vessels within the respiratory system to dilate right because it allow for a lot of fluid to come into the area and leak out and make a lot of secretions you don't want a lot of secretions within the lungs because you want to have open area open airways that you can get as much oxygen in and out so what do you want to do to the secretions you want to decrease it so two things can also happen happen here is it's also going to decrease secretions by acting on the glands directly and it's going to cause vaso Constriction of bronchial arteries. Make sure that you understand I'm saying bronchial arteries. I am not talking about the pulmonary arteries. These are completely different. Okay, those are more auto-regulated, auto-regulation, that type of control. Okay, cool. Now the next thing that we have to talk about is what do we call this? Well, specifically if it's going to the heart, what do you think we call that? We called it the cardiac. plexus. If it's going to the esophagus, we're going to call this the esophageal plexus. If it's going to the lungs, we're going to call this the pulmonary plexus. But here's one more thing that we have to understand, right? So I said that it was mainly coming from the superior, middle, and inferior. That's not always the case. There's also other contributions. Remember I said here that there was T1, T2, T3, right? Well, guess what else? There's also going to be, so you can have these fibers that can actually go straight up here, or they can come and synapse in this area. So let's say that it actually synapses here, or this guy comes over here. So let's say now that it comes here and synapses, or it comes here and synapses, comes here and synapses, mainly T1 to T4, but you can have some contributions here from T5. Okay? So you can have T1 to about T4. But if you want, we'll throw in another one there, which is going to be T5. Now what can happen? Some of the fibers from T1 to T3 can go up. Right, so here let's show that kind of like this. Or some of them can go to the actual cell bodies within the chain ganglia. Remember what I told you? They don't have to go out through the greater rhamic communicans. They can go out as their own nerve. What was that called? It's called a splanchnic nerve. And so some of these fibers here, so T1, T2, T3, T4, and again take it with a grain of salt. There's a lot of variability here, but even T5. And remember, I'm saying a lot of variability because sometimes you're going to read in different books that certain nerves might go to different ganglions, certain nerves might not go to this one, certain nerves might go to the other one. So just remember, there's a lot of variability in these textbooks, okay? Alright, so that's that. Alright, so we talked about the cardiac plexus, esophageal, pulmonary, and the carotid. Now let's go to the next one. The next thing we're going to talk about is we're going to go to this structure called the celiac ganglion. So we're going to go from a specific portion now. We're going to go, because now we're getting ready to go into the abdomen. And we're going to go from T5 to about T9 now. That's the one we're going to focus on. Okay? So we're going to focus primarily here on T5 to T9. Let me get this kidney and ureter out of the way. Okay. So first things first. Remember I told you, some of these fibers, they can go to a chain ganglion. Some of them they don't have to. They can pass right through it, right? They can go into a collateral ganglion. So now that's what we're going to talk about. So let's say that this T5 passes right through. T6 passes right through, T7 passes right through, T8 and T9 pass right through their chain ganglia. They don't synapse there. And they come out, right, as some type of splanchnic nerve. This splanchnic nerve right here, what do we call this bad boy? We call this nerve the greater splanchnic nerve. Now the greater splenic duct nerve pretty much extends from T5 to T9. Now what's the main ganglia that it's going to go to? The main ganglia here that it's going to go to is going to be right around here. You know that there's the aorta, right? You have the aorta, and right around the aorta you have this paired ganglia. This paired ganglia is actually going to be called the celiac ganglia. So let's actually show that guy right here. Here's the cell body. I'm just drawing one, but remember there's multiple cell bodies here. Synapse is right there. There's the ganglion. What is this ganglion called? This ganglion is called the Celiac Ganglion and remember this is a prevertebral or collateral. Now from the Celiac Ganglion, you remember what the artery was that actually moves right where the Celiac Ganglion, the nerves are gonna move in that same area. It's called the Celiac Trunk, right? Celiac trunk gives off multiple branches but we're gonna pick the main, the most common ones, right? So if we come up here, look what's gonna happen here. We're going to have a heck of a supply here. Okay, so what is this going to be? So ciliary ganglion is going to give branches off, celiac trunk again, and the celiac trunk, if you remember, gives off multiple branches. We're going to focus on the more common ones, right? Big one right here, stomach. So it's going to go to the stomach. And when it goes to the stomach, what do you think you're going to want to do? You're going to want to inhibit the actual peristalsis, inhibit the secretions. So two effects here for this guy. Inhibit peristalsis. Because again, you don't want to be contracting your stomach and trying to focus a lot of that energy and muscles on basically focusing on digesting food. That's not your sole focus, right? So you want to try to inhibit the peristalsis. Another thing here is you're going to want to try to inhibit some of the secretions there too. But the main thing that we're going to try to do here is remember the blood flow. right, the splanchnic circulation. You don't really want a lot of blood flow going to the stomach during a sympathetic situation. So what are you going to want to try to do to the actual blood flow to that area? You're going to try to decrease it. So what are you going to do to the vessels? You're going to constrict the blood vessels. So you're going to constrict the blood vessels going to the stomach. And if you do that, by default, it's going to do two things. One is it's going to decrease the absorption process, right? Because there is certain things that do get absorbed across the gut, specifically in the stomach, like lipid soluble substances, like aspirin and alcohol. But another thing is it's going to decrease some of the actual secretions. Okay. There is another exception here where it actually can. There's a sphincter muscle right here. It's actually called the pyloric sphincter. I'm not going to talk too much about it, but if you really do want to remember, what it can actually do here is it can act on the pyloric sphincter. And when it acts on the pyloric sphincter, it can constrict the pyloric sphincter to prevent chyme from moving from the stomach into the duodenum, basically slowing down the digestive process. basically. So if you do want to remember that, it is a different one where it actually can cause Contraction of pyloric sphincter. They call this, whenever that happens, they call it the enterogastric reflex. Okay, which is basically inhibitory reflex. It's very common and happens normally within the actual GI tract processes. But anyway, the reason why that's a little bit different is you might be like, wait, how is it causing contraction? How is it inhibiting it? Here, it's dependent upon receptors. For example, this is alpha 1, this is usually beta 2. Okay? But again, we'll make a video on that specifically. All right, now we're going to go to the liver. The liver, what is it going to try to do to the liver? The liver, it's mainly going to focus on trying to do a special thing here. One of the special things about the liver is that the liver can actually break down glycogen into glucose, which is important whenever our blood sugar levels need to be high so we can get our muscles contracting to be able to fight Chuck Liddell or run from Chuck Liddell, right? So what are we going to do here? The big thing here is we're going to do what's called... Glycogenolysis. That's going to be the big thing here. We're going to want to try to cause glycogenolysis to occur for the liver. Alright, now the biliary tree here, you're not going to really want the actual gallbladder contractions to occur. You're not going to want to be able to release bile. You're not really focusing on emulsifying fats and digesting and absorbing lipids, right? So you're going to want to try to inhibit the biliary contractions, right? So you're going to want to be able to Decrease biliary tree contractions and flow. Here, I like that better. Let's say decrease biliary tree flow. Okay, biliary tree flow. Because again, you're not really focusing right now on trying to be able to get rid of the bile and help to cause the emulsification of fat. That's not really your focus at that point. Alright, again the pancreas. The pancreas, you know that there's structures here within the pancreas. They call these guys the islets of Langerhans. And the islets of Langerhans have alpha cells and beta cells. Now, the beta cells are responsible for secreting insulin. The alpha cells are responsible for secreting glucagon. Now, in this situation, insulin wants to be able to decrease your blood glucose levels. You don't want that. You want to increase them. So, what do you think it's going to do to the insulin production here? It's going to focus on trying to decrease insulin production. And vice versa, I want the other hormone to even act synergistically with me to enhance the blood glucose levels. So I'm going to inhibit the beta cells but stimulate the alpha cells. So I'm going to want to try to increase glucagon production here. Okay. All right. And there is fibers that can go to the splenic capsule here, to the spleen. Not necessarily super important to be honest with you, but it can cause the splenic capsule to have a slight contraction. So it can go to the spleen and cause like a splenic contraction. Again, not super important in this situation. Not really significant to the fight or flight response. Okay, so the big thing here that we were able to grasp here is that from the celiac ganglion, it's going to supply the stomach. cause the contraction of the pyloric sphincter, inhibit peristalsis, decrease absorption secretions, it's caused glycogenolysis, decreased biliary tree flow, and it's going to try to inhibit the insulin production, the glucagon production, and increase glucagon production, and again it can cause the splenic contraction of the outer capsule. Also there is, remember the celiac trunk does supply the proximal half of the duodenum, and again if you remember that it's going to decrease the absorption and the secretions of that area also. Okay, so it's not just the stomach but also remember the proximal half of the duodenum. Alright, sweet deal. Now, the greater splanchnic nerve has another point that it goes to. And remember, I'm telling you guys this because you have to understand that there is so much variability here. Now, there is another part here, right, that the greater splanchnic nerve can have a branch that comes off here and goes to the adrenal medulla, okay? Now, these are odd because you're going to notice here, wait, where the frick is the ganglion? In this case, there isn't really any collateral ganglion. This is a weird exception where we say that sympathetic preganglionics are short and sympathetic postganglionics are long. This is kind of like the opposite in this case. So now the postganglionics are really short. They're actually called, in this area, they call it the chromophin cells. The chromophin cells are really important because they're acting like the postganglionic fibers. And what happens is this is an example of what's called a Intramural ganglion. Okay, you're like, oh, I thought that was just for the parasympathetic. This is just one of the exceptions of the sympathetic. And again, as a result, it can... Act on these chromophane cells, which are very cool because they can release two different chemicals directly into the circulation. One is called norepinephrine, and the other one is called epinephrine. Okay, and these guys can go all the way, widespread. They can have that very, very widespread diffuse effect, which is a very powerful effect, as compared to parasympathetic, which is more localized. Okay? Alright, so that's that part. So we can go to the intramural ganglion. Okay, what else? There's another one. The greater splenctic nerve can also give off another fiber here. And again, remember, take this with a grain of salt. It's not always the same thing. It's not always clear cut here. But it can give off another one that goes to another ganglion. Okay? There's another ganglion here. And this guy is called the superior mesenteric ganglion. So what are we going to have right here? We should have, let's write it here, below it, superior mesenteric ganglion. Okay, now this one's very interesting also. Superior mesenteric ganglion, remember the blood supply, superior mesenteric artery. So the actual superior mesenteric artery specifically supplied a couple different structures. One is it can actually supply the cecum. It can supply the ascending colon. It can supply the actual transverse colon up to about around the actual left colic flexor like the proximal two-thirds. And it can also supply the duodenum, the distal half, and it can supply the jejunum and the ilium, right? This is the easiest one to think about, honestly. If it's acting in this area, right, it's going to the duodenum. the jejunum, the ileum, the ascending colon. What do you think it's going to do? And even the proximal two-thirds of the transverse colon. It's just going to inhibit the digestive processes. So basically, the whole result out of all of this here is it's going to basically try to, okay, we'll write this one coming down, this right here, the result of this is it's going to actually cause what? Decrease peristalsis. What else? Decrease and the absorption because it's going to constrict the blood vessels and if it constricts the blood vessels it's not really relevant within the large intestine but it is important within the jejunum the ileum and the distal half of the duodenum but it's going to decrease the secretion processes also okay so again you can just remember decrease peristalsis decreases absorption and decreases accretion if you really want to be specific though the absorption and secretion is a little bit more important within the small intestine not as important within the the actual large intestine because they don't really play big role in absorption. They really only absorb water and electrolytes. Okay, got that guy. And if you want there is a little information that goes to the appendix, but we're not going to talk about that. Alright, so we got the greater splanctic nerve. Now we're going to go to the next guy. Alright, next one is going to be from T10 to T11. So this was for the greater splanctic nerve, right? This is going to be for what's called the LSN, the lesser splanctic nerve. Okay, so T10, T11, again these preganglionic fibers come out. What can they do? They can just, they can either synapse there, become a part of the gray rima community cans, and then go into the spinal nerve and supply pylomotor, pseudomotor, vasomotor, or they can pass right through the frickers. Boom and boom. If these guys come out, what happens is, and if it does, it can go to a ganglion. Now again, I'm gonna keep saying this because there's so much variance in these textbooks. But for the most part, this is what I was able to find is that the actual T10, T11, they come to a specific ganglion. And this ganglion is actually called the aorticorenal ganglion, right? So we got T10, T11, which is going to pass right through. And then again, what is this nerve called? Lesser splanchnic nerve. Okay, getting a little lazy, sorry guys. Lesser splanchnic nerve. Now that'll go to the aorticorenal ganglion. The aorticorenal ganglion will take these postganglionic fibers out. And where are they gonna go? They're gonna go specifically to the good old kidney, right? So here let's have our kidney here, let's have the ureter, right so we're going to have this guy here. So what What I'll do is, they'll synapse here in the aortic renal ganglion and the aortic renal ganglion is going to go to the kidney and it's actually going to go to the ureter. Now, when it goes to the kidney and the ureter, what are you going to try to do? Are you going to try to pee on Chuck Liddell? No, you don't want to pee on Chuck Liddell. That might happen, but that's not normal. But what you want to do is, is you don't want a lot of blood flow going to the kidneys and you don't really want to make urine. So, as a result, what are the two things that you would expect to happen here? One is I'm going to decrease... Urine production, okay, that's one big thing. What's another big thing? Well, here's a little weird thing. There's actually these things in here, in the actual kidney, we're not going to zoom in on it, but the JG cells, the juxtaglomerular cells. The juxtaglomerular cells are really important. Why? Because what they do is they respond by beta-1 adrenergic receptors. They can release a chemical called renin and renin can set off the angiotensin 2 cascade. which can cause Adosterone, ADH, all these different hormones to get produced, which are trying to increase your blood pressure. So in that response, what else could I have? I could have what's called renin release. Okay, but again, remember the urine production? It's usually due to what? Remember I said it's decreasing the blood flow. So it's going to decrease the blood flow, mainly by causing vasoconstriction to the blood vessels going to the kidney, diverting that blood away from the kidney. so that we can send it to more important vital organs. That's the same thing with the stomach. Again, you're decreasing absorption and secretion, or the entire GI tract. If you're doing that, you're constricting the blood flow to it, so you can divert the blood away from those organs, so you can send it to the muscles, or the brain, or other different organs needed for you to do the flight or fright situations. Okay? Alright, so we got that one. T12 is pretty easy also. This one's actually a little, a lot easier. It can pass right through T12. I mean, it can go right through the chain ganglion. And again, I'm going to keep saying it. Take this with a grain of salt. There is these weird type of cells, diffuse ganglion cells. And they're kind of like found, like they're kind of diffuse and kind of widespread around this area here. I'm going to kind of represent it like this. These diffuse ganglion cells are important because when T12, the preganglionic fibers, they can come and synapse on some of these diffuse ganglion cells. When they do. These guys can enter into the kidney as a part of what's called the renal plexus, right? So what do we technically call this? It can synapse. Technically, we call this the renal plexus, okay? Which again can help to support the fibers from the aortic or renal ganglion by causing random release, decreasing urine production. But again, more of it is trying to be able to decrease urine production. Another thing that can happen with the urine production is if you don't want The actual ureter to contract, what are you going to want to do? What do you want to do to the ureter? You want to be able to decrease the peristalsis of the ureter. Okay, so that's another effect that you can get out of the renal plexus and the fibers from the aortic or renal ganglion. You're not going to want the actual ureter to be contracting. You don't want to focus on making urine, right? All right, my darn knees. All right, so we got here T12. I guess I should tell you what this guy's called. This is called the least splanchnic nerve. Okay? So this fiber right here, I'm going to denote it with L. Actually, I'm going to have to write it here because that's the same thing here. This is called the least splanchnic nerve. Okay? Okay. We are so close, guys. Alright, let's do L1 and L2 and sometimes L3. Okay, these are going to be your lumbar splanchnic nerves. Okay, lumbar splanchnic nerves. So again, L1, you can have this guy pass through. L2, pass through. L3, pass through, right? Now, if they pass right through, they don't go to the Chang ganglion, this is kind of important here. They can continue to keep passing through here. And here's where it gets interesting. We're going to kind of come up over here, right? And there's going to be a ganglion over here, okay? There's going to be a ganglion right over here. We're going to kind of finish what we didn't get to over here. So now, there's going to be a ganglion over here. where these lumbar splenic nerves can actually come to and innervate. This ganglion is called the inferior. Mesenteric ganglion. Okay, now from the inferior mesenteric ganglion, remember the inferior mesenteric arteries. Okay, the inferior mesenteric artery. What happens with the inferior mesenteric artery? It supplies the descending colon, sigmoid colon, upper rectum, and The distal one-third of the transverse colon. Now, what do you think you're going to try to do here? The overall result. You're going to want to try to decrease. Peristalsis. You're going to want to try to be able to, that's the main function to be honest with you, is decrease the peristalsis here. Okay? So as a result here, the main function for this one is you're going to want to try to decrease the peristalsis. Alright, you're not going to want to try to poop or defecate in that type of situation. That's for parasympathetic, when you're calm and you're resting, you're digesting, defecating, urinating, alright? So that's going to be for that part. Alright, so now we're going to talk about the innervation to the bladder and the interneuritis sphincter. So we talked about how L1, L2, and L3 can go out here. Now sometimes what can happen is some even from T12, they can actually kind of come down here and so can L1 and L2. And even L3 here can actually, what happens is sometimes they can even pass down to L4. But either way, nonetheless, some of these fibers all the way down from about T12, sometimes even T11, down to about L2, L3. They can pass through, right, and they can come to an area right over here. There's two plexi over here. One, let's actually draw it like this, there's actually two plexi over here. One is called the superior hypogastric plexus and the other one is actually going to be what's called the intermesenteric plexus. So again, L1, L2, L3 and even T12, sometimes even T11. They can come down, right, through these actual chain ganglia, come out, and they can go to two ganglion over here. One can be called the superior hypogastric plexus, and the other one is called the intermesenteric plexus. So again, what is this one right here called? We'll put this as the superior hypogastric ganglion. Or we can have over here this weird sucker called the intermesenteric plexus. This is actually in between, as you can hear, between the superior and inferior mesenteric arteries. So it's kind of extending between these and allows for things to go up and go down around that area. But again, what can happen is... We're not going to talk about the things from the intermesenteric because as I said, things can go up into the superior mesenteric ganglion. They can go down into the inferior mesenteric area. So they can go and follow superior mesenteric artery or inferior mesenteric artery. Some of them can even follow some of the actual hypogastric nerves. There's so many different areas that can come from this point. So what I'm just going to do here is I'll show that it can either go this way. It can go that way. Some of the fibers can actually even go over here. Okay. So superior hypogastric ganglion. gives these fibers here that can go to the internal urethral sphincter and can go to what's called the detrusor muscle. Okay, so this big, big muscle here, which is basically the muscularis externa of this bladder, is called the detrusor muscle. Alright, if you watched our video on micturition reflexes, we'll also give you a little bit more detail if you want. But there's beta 2 and beta 3 adrenergic receptors in the detrusor muscle. Whenever it acts on that muscle, it relaxes the muscle. It inhibits it from undergoing contraction. So what is that going to do to this guy? It's going to decrease contractions. Basically trying to prevent the process of voiding or micturition. All right, down here you have the internal urethral sphincter. Now this one's different. Now this one actually what happened? It did not contract. Guess what's going to happen here? The sucker is going to constrict. Prevent you from peeing your pants, right? So, or actually almost peeing your pants. So there's actually alpha-1 adrenergic receptors in this guy, but it's going to act on this guy, the internal urethral sphincter, and actually cause constriction or contraction of the sphincter. But remember, this is the internal urethral sphincter, not the external. External is under voluntary somatic control. All right. Now remember the superior hypogastric ganglion or plexus they call it. This one's interesting and the reason why is is it actually gives off things called hypogastric nerves. The right hypogastric nerve and the left hypogastric nerve. And those are pretty much the main contribution into this last thing that we're going to talk about called the inferior hypogastric plexus. So I do want you to remember that the main input going down into the actual gonads, the ovaries and the testes, is going to be the contributions from the superior hypogastric plexus. The right hypogastric nerve, left hypogastric nerve, will eventually become the inferior hypogastric plexus. But before we finish that off, there's a part down here, right? So what happens is, remember I said here, remember I said to go into the bladder, it could be from like L1, L2, L3, and it can even go out to the ganglion around L4. It can even be up to T12, T11. Well, same thing for the gonads. The gonads can actually extend from T10 too. So T10 can actually give extensions. and so can T11. So you can have extensions from T10, T11, L1, L2, mainly from T10 to L2. Okay, so it's pretty much going to go to about L2 here. What they do is they can come into these chain ganglia, right, and they can come out around the sacral region of these actual chain ganglia, around the sacral region. And what happens with these guys is they're going to go and supply the gonads. Okay, so it's going to go and supply the gonads. So for that you remember that there's the uterus for the female, there's the vagina, right? There's also some of other tissues around that area like the actual oviducts, the ovary. For the male it's going to be like the penis, the scrotum, right? So around that area there. So this is important. So what is it going to do? Okay, for the male, what kind of effect would it have in the male? Specifically, It's designed to initiate ejaculation. Okay? So you can remember this by parasympathetic point for the erection and sympathetic shoot for the ejaculation. And then for the female, this one, it actually is kind of interesting. It can act on the uterus, right? And generally, it wants to cause the contractions of the uterus. So it actually can cause uterine contractions. But whenever a woman's pregnant, What happens is it switches receptors, okay, from alpha-1 to beta-2 so that the uterus doesn't contract because you don't want to pop a baby out whenever you're pregnant, right? So it can change. So remember, uterine contractions is for non-pregnant women, but it does actually change when they're pregnant, right? It switches the receptors from alpha-1 to beta-2. But it can cause uterine contractions or ejaculation within the male. There's also other structures called the prostate gland within the male. right, the prostate gland, the seminal vesicles, so it can actually cause those guys to produce what's called seminal fluid. All right, not as super important for these guys, but again, what is these nerves here called? These ones here, son of a gun, these are called your sacral splanchnic. So this area here is called your sacral splanchnic nerves. And remember, this one here going to the inframesenteric ganglia and the intermesenteric plexus and the superior hypogastric. is called the lumbar splanchnix. And remember, like I told you, superior hypogastric ganglion can give off things called right and left hypogastric nerves. So these can be what's called your hypogastric nerves. And again, the hypogastric nerves are the main contributor to... this structure down here because what happens is the sacral splanchnics they come out to some diffuse ganglion cells out here also and what happens is the main main contributor that innervates the gonads the main one let's actually put this one in pink so that we can brighten it up here is called the inferior hypogastric plexus Okay, so the inferior hypogastric plexus is the main nerve that's going to supply the gonads, right? And it can get two contributions. Very little of it, very minute amounts, come from the sacrosplastic nerves, from like T10 to L2, but a good, good, good portion of them, the more significant contributor, is going to be from the superior hypogastric ganglion, which splits it into right hypogastric nerves and left hypogastric nerves, will eventually become... and merge with the sacral splenctics and form what's called the inferior hypogastric plexus, which again will supply the gonads. All right, so before... Before we finish this off on the sympathetic outflow, I need to talk about one last thing I promise. And this is going to be some of the control. So you know there's a tissue of gray matter, which is a part of the diencephalon right here. It's called the hypothalamus. There's also other structures in here. Like, for example, you can have what's called limbic nuclei. Right? And even parts of your cortex. But here's the important thing. The sympathetic nervous system actually has contributions from the hypothalamus and it has contributions from the limbic nuclei. In certain situations, it can even have cortical control also. So sometimes it might even have cortical control. Not very much though, but it can sometimes have some cortical control. But for the most part, the main ones is the limbic nuclei have a big effect on the sympathetic nervous system and the hypothalamus. Okay, the only reason I say cortical controls is that there's things called biofeedback techniques, where you actually can, like on your own, control your heart rate. So there is some weird situations in which there can be cortical controls, but mainly the limbic nuclei and the hypothalamus are some of the big, big structures, tissues of gray matter within the cerebrum. that actually can contribute to innervating or stimulating the sympathetic nervous system. Because you can have these things like these presynaptic fibers that can come down and stimulate these cell bodies right here. So again, these presynaptic fibers, they can come out and stimulate these cell bodies here and activate these preganglionic motor nerves to come out and stimulate the postganglionic and go and innervate the target organ. So remember, this sympathetic control can have a higher brain functioning control. right hypothalamus has sympathetic tissue that can actually have presynaptic fibers and come down and stimulate the cell bodies in the lateral gray horn or the intermediate lateral column and so can the limbic nuclei and in certain situations where people can have biofeedback techniques they might even have a little bit of cortical control all right all right ninja nerds i want to thank you guys so much for watching this video if you guys did watch this video if you got through the whole thing man you guys are awesome i hope you guys like this video i hope that You guys really learned something. If you did, please hit the like button, comment down in the comment section, and please subscribe. Also, check out our Instagram, our Facebook, and our Patreon account. Please, guys, every dollar counts. It helps us to make the highest quality videos for your guys'enjoyment. All right, engineers, as always, until next time.

Hi Ninja Nerds! In this video we're going to talk about the sympathetic nervous system. If you guys haven't already, please go watch the video on the introduction to the autonomic nervous system.

We discuss a little bit of a little brief introduction into talking about the different types of ganglia and a little bit on the sympathetic nervous system and the parasympathetic. In this video we're going to go into a little bit more detail on the actual specific splanchnic nerves, right? And their target organs and then the functions of those target organs, okay? Before we do that though, I want to talk about this thoracolumbar outflow.

Alright, so let's go ahead and talk about that first. So, if you remember, we talked about this in the autonomic intro video, that from T1 to L2, and again, take a little bit of grain of salt, there's some variance in there, sometimes it can be to L3. This is called the thoracolumbar outflow.

It's a sympathetic outflow. Now, where are these, what are these blue things? These blue things, if you remember, are the cell bodies of the preganglionic motor neurons which are located in the intermedial lateral column or the lateral gray horn.

I think that one's easier to say, but either way remember that you can find these blue guys here. These are the cell bodies of the preganglionic motor neurons of the sympathetic nervous system found in the lateral gray horn or the intermedial lateral column. All right, now what we're going to do is I want to talk about the outflow to these target organs.

So we have these things on the side here, right? These are called your ganglia. What is a ganglia?

A ganglia is just a group of cell bodies in the peripheral nervous system, which is outside the CNS, which is made up of the brain and the spinal cord, right? So outside of the brain and the spinal cord, you have these groups of cell bodies. They're called ganglia.

If they're located on the side, they're called chain ganglia. If they're located in front, remember they were called pre-vertebral or pre-aortic or sub-diaphragmatic or collateral. A whole bunch of darn names for the same thing, right?

What we're going to talk about in a lot of this video is the collateral ganglions. Okay, which we're going to stick with collateral or prevertebral, right? But I want to talk about these chain ganglia first, these top ones. This one right here, if you come up, an extension up here, these chain ganglia up to the cervical region, right around like C2 about, this is actually you're going to have what's called your superior cervical ganglia, which we're going to put SCG. You'll have another one at this level, which is the middle cervical ganglion.

MCG or the inferior cervical ganglion which is the ICG but again there are some variants in different people sometimes the inferior cervical ganglion is fused with T1 they call it the stellate ganglion not necessarily super important but again wanted you guys to understand the variants here what I want to do is I want to talk about the preganglionic flow to the superior cervical ganglion and then out okay via to the head and neck structures that's we're going to start with first so first things first Generally, from anywhere from about T1 to T3, okay, about T1 to T3, these guys can come out, right? So here's what I'm going to do. I'm going to bring this guy in here.

It's not going to synapse in that chain ganglia. It's going to move upwards, and it can synapse on the cell bodies in the superior cervical ganglion. And again, this can come from T1.

It can come from T2. Or it could even come from T3. Alright?

When these fibers move up, they can move up through the inferior cervical, middle cervical, up to the superior cervical ganglion. And synapse in the cell bodies here. From this point, they can then come out. When they come out, guess what these guys do?

You know there's a big artery, right? There's a big artery here. You know, your heart, you have the common carotid artery.

The common carotid artery actually bifurcates into the external carotid artery and the internal carotid artery. What happens is you can have this nerve fiber kind of swirl around the internal carotid artery and when it does that it forms a special plexus. We call this the carotid plexus.

And it can actually come off and go to different portions around the head and the neck. The main ones we're going to talk about is going to be first the eye. Okay, so it's going to supply a lot of different structures here.

Okay, the first one that we're going to talk about here is going to be the eye, right? Now, if you remember, those are the preganglionic, the blue. The black are the postganglionics. They release norepinephrine. There's only one exception to it, and we'll talk about that.

And it's going to be the sweat glands. But here, what's going to happen is this guy's going to release norepinephrine. Now, what area is it going to act on in the eye?

You know what there is? Around the iris. You have a specific muscle there. We talked about in the actual special senses videos. There's the Iris right has what's called the dilator pupillae right and think about these things logically in a sympathetic situation your fight your flight your fright situations what are you gonna want to do let's pretend that I don't know Chuck Liddell he's getting ready to come at you he's chasing you what's gonna happen well you want to be able to see all different types of options right so what would your pupils want to do in that situation would you want to only see things like very small amount of areas or would you want to be able to see a lot of stuff you want to see a lot of stuff So what's going to happen is it's going to release norepinephrine on this muscle here called the dilator pupillae.

So what can it do? It can act on what's called the dilator pupillae. And when it acts on the dilator pupillae, it causes pupillary dilation.

If it acts on the dilator pupillae and causes pupillary dilation, what does that allow for? That allows primarily for far vision. allows more light to come in.

You're going to have a little bit more exception for the far vision. What else? It's also going to act on a muscle right here around the ciliary body. They call it the ciliary muscle. So it's also going to act on the ciliary muscle called the ciliaris.

When that contracts, what it does is, is it actually helps the lens to become more flattened. When the lens becomes more flattened, it helps us to be able to see very, very far too. It's called accommodation.

So the ciliaris allows for what's called accommodation and this accommodation can lead to the assistance in far vision right that's important then it's also gonna act in that remember I said the head and neck region we had a lot of glands in this area you know we have the salivary glands like the submandibular the sublingual the parotid salivary glands right and even other glands too associated with this but These are your main salivary glands, right? So the main thing is going to be your salivary glands. Let's put here salivary glands.

And again, remember submandibular, sublingual, parotid. What's going to happen is they're going to release chemicals like norepinephrine, which can act in two places. One is that norepinephrine, remember this was norepinephrine, which is acting here.

It can also release norepinephrine, which can act on two places. One is it could act directly on the blood vessel. It can act on the tunica media. You know there's the tunica media, the smooth muscle within the vessel wall, which constricts. When it constricts, it decreases the blood flow to the salivary glands, which decreases the actual substances that you can take for these salivary glands to take from the blood and put into the saliva.

That's one important thing. The next thing is it also is going to act on the salivary glands directly. There's different types of adrenergic receptors.

We'll have another video on that. When it acts on the salivary glands, it actually causes them to switch their mucus production. into producing more mucin, which is a glycoprotein which helps to thicken the mucus.

So it's going to cause two different effects. One, it's going to cause a thick, viscous, thick, and viscous mucus production. Okay, so it's going to cause a thick, viscous mucus production.

Alright, now, what about other glands? There's other glands besides salivary glands in this area. You know there's another one?

Lacrimation. Right? So you also have what's called these lacrimal glands.

So the other ones here called lacrimal glands. Now your lacrimal glands, what happens is norepinephrine can also act on the blood vessels in this area, constrict them, decrease the blood flow through the area, which decrease the lacrimation. Or it could act directly on the lacrimal glands and decrease lacrimation, right? So it's going to try to decrease lacrimation. Okay, so that pretty much covers this.

Now what was this thing here called which comes off the superior cervical ganglion? They pretty much call this the carotid plexus. Okay, all right that covers that part.

Now the next thing here is really important. Now there's other things that can come from the superior cervical ganglion and actually can join on to some of the actual spinal nerves and if it joins with some of the spinal nerves it can go to supply your Erectropeli. It can go to supply the actual blood vessels, the vasomotor supply, or it can also do what? If you remember, it can also code to the pseudoriferous sweat glands, okay, which are going to be important for pseudomotor control, which is sweat production.

All right, but let's talk about these other ones here. So now we're going to have the middle cervical ganglion and the inferior cervical ganglion. These can give off branches too, but the most important branches for these guys are going to be Specifically, structures that are going to the heart, the lungs, and the esophagus. Okay? So they're going to give off fibers here, and these fibers here are going to be the We're going to go specifically to the heart, the lungs, and the esophagus.

Okay, now another thing is the superior cervical ganglion can also give off some fibers too. It can also give off. So sometimes we call this the superior middle inferior cardiac nerve or plexus, right?

And these are your sympathetic fibers. And what they're doing is they're going to three different targets. And what are these targets? One is it can go to the heart. If it goes to the heart, it acts mainly on two different areas.

One is your nodal cells. Your nodal cells are important for heart rate. So what it's going to do is it's going to try to increase the heart rate. It's going to try to cause positive chronotropic action.

So what's the overall effect here? It's going to try to, let's do a different color, let's say it increases heart rate. So one thing is it's going to increase heart rate. They call that positive chronotropic action, right? Another thing is it can act on the myocardium, the contractile muscle cells.

If that happens, it can increase the contraction power. If that does that, if we increase contractility, we increase what's called cardiac output. And if you increase cardiac output, eventually that could increase your blood pressure.

Okay, so that's a pretty cool thing there, right? All right, what else? It can act in the esophagus.

Now... Generally, you don't, whenever you're in a flight or flight situation, or you don't want to be able to worry about digesting food, no. You don't really care about that. So it's going to try to decrease peristalsis of the esophagus.

So for the esophagus, it's going to decrease peristalsis of the esophagus and certain secretions of the esophagus within the serum mucus. You have certain types of glands within this area, the esophageal glands. Okay, the lungs, the respiratory system, the specific...

area that is affecting though is the bronchi. You know the bronchial smooth muscle? There's bronchial smooth muscle here that actually control the diameter of the airway.

They control the airway resistance. So if the sympathetic nervous system is gonna act here, think about that. What are you gonna do if Chuck Liddell is coming at me, one of the toughest UFC fighters in history, right?

What's gonna happen? I'm gonna, I'm gonna hyperventilate. I'm gonna get really scared. So you're gonna want to be able to allow for the dilation of the respiratory bronchioles. Because you're gonna want to be able to run away, right?

Have as much air getting into your your blood as possible, as much oxygen, because you want to run away from that guy. Right, so what's going to happen here? It's going to dilate the bronchioles. So it's going to cause dilation of the bronchioles. Now another thing it can do, remember that it actually does have the ability to go to the vascular smooth muscle, I'm sorry, the vascular smooth muscle within the blood vessels in this area.

Now why that's important is, is you don't want your blood vessels within the respiratory system to dilate right because it allow for a lot of fluid to come into the area and leak out and make a lot of secretions you don't want a lot of secretions within the lungs because you want to have open area open airways that you can get as much oxygen in and out so what do you want to do to the secretions you want to decrease it so two things can also happen happen here is it's also going to decrease secretions by acting on the glands directly and it's going to cause vaso Constriction of bronchial arteries. Make sure that you understand I'm saying bronchial arteries. I am not talking about the pulmonary arteries. These are completely different. Okay, those are more auto-regulated, auto-regulation, that type of control.

Okay, cool. Now the next thing that we have to talk about is what do we call this? Well, specifically if it's going to the heart, what do you think we call that? We called it the cardiac.

plexus. If it's going to the esophagus, we're going to call this the esophageal plexus. If it's going to the lungs, we're going to call this the pulmonary plexus.

But here's one more thing that we have to understand, right? So I said that it was mainly coming from the superior, middle, and inferior. That's not always the case.

There's also other contributions. Remember I said here that there was T1, T2, T3, right? Well, guess what else?

There's also going to be, so you can have these fibers that can actually go straight up here, or they can come and synapse in this area. So let's say that it actually synapses here, or this guy comes over here. So let's say now that it comes here and synapses, or it comes here and synapses, comes here and synapses, mainly T1 to T4, but you can have some contributions here from T5.

Okay? So you can have T1 to about T4. But if you want, we'll throw in another one there, which is going to be T5. Now what can happen?

Some of the fibers from T1 to T3 can go up. Right, so here let's show that kind of like this. Or some of them can go to the actual cell bodies within the chain ganglia. Remember what I told you?

They don't have to go out through the greater rhamic communicans. They can go out as their own nerve. What was that called? It's called a splanchnic nerve.

And so some of these fibers here, so T1, T2, T3, T4, and again take it with a grain of salt. There's a lot of variability here, but even T5. And remember, I'm saying a lot of variability because sometimes you're going to read in different books that certain nerves might go to different ganglions, certain nerves might not go to this one, certain nerves might go to the other one. So just remember, there's a lot of variability in these textbooks, okay?

Alright, so that's that. Alright, so we talked about the cardiac plexus, esophageal, pulmonary, and the carotid. Now let's go to the next one. The next thing we're going to talk about is we're going to go to this structure called the celiac ganglion. So we're going to go from a specific portion now.

We're going to go, because now we're getting ready to go into the abdomen. And we're going to go from T5 to about T9 now. That's the one we're going to focus on.

Okay? So we're going to focus primarily here on T5 to T9. Let me get this kidney and ureter out of the way.

Okay. So first things first. Remember I told you, some of these fibers, they can go to a chain ganglion.

Some of them they don't have to. They can pass right through it, right? They can go into a collateral ganglion. So now that's what we're going to talk about.

So let's say that this T5 passes right through. T6 passes right through, T7 passes right through, T8 and T9 pass right through their chain ganglia. They don't synapse there.

And they come out, right, as some type of splanchnic nerve. This splanchnic nerve right here, what do we call this bad boy? We call this nerve the greater splanchnic nerve. Now the greater splenic duct nerve pretty much extends from T5 to T9. Now what's the main ganglia that it's going to go to?

The main ganglia here that it's going to go to is going to be right around here. You know that there's the aorta, right? You have the aorta, and right around the aorta you have this paired ganglia. This paired ganglia is actually going to be called the celiac ganglia. So let's actually show that guy right here.

Here's the cell body. I'm just drawing one, but remember there's multiple cell bodies here. Synapse is right there.

There's the ganglion. What is this ganglion called? This ganglion is called the Celiac Ganglion and remember this is a prevertebral or collateral.

Now from the Celiac Ganglion, you remember what the artery was that actually moves right where the Celiac Ganglion, the nerves are gonna move in that same area. It's called the Celiac Trunk, right? Celiac trunk gives off multiple branches but we're gonna pick the main, the most common ones, right?

So if we come up here, look what's gonna happen here. We're going to have a heck of a supply here. Okay, so what is this going to be?

So ciliary ganglion is going to give branches off, celiac trunk again, and the celiac trunk, if you remember, gives off multiple branches. We're going to focus on the more common ones, right? Big one right here, stomach. So it's going to go to the stomach.

And when it goes to the stomach, what do you think you're going to want to do? You're going to want to inhibit the actual peristalsis, inhibit the secretions. So two effects here for this guy.

Inhibit peristalsis. Because again, you don't want to be contracting your stomach and trying to focus a lot of that energy and muscles on basically focusing on digesting food. That's not your sole focus, right? So you want to try to inhibit the peristalsis.

Another thing here is you're going to want to try to inhibit some of the secretions there too. But the main thing that we're going to try to do here is remember the blood flow. right, the splanchnic circulation. You don't really want a lot of blood flow going to the stomach during a sympathetic situation. So what are you going to want to try to do to the actual blood flow to that area?

You're going to try to decrease it. So what are you going to do to the vessels? You're going to constrict the blood vessels.

So you're going to constrict the blood vessels going to the stomach. And if you do that, by default, it's going to do two things. One is it's going to decrease the absorption process, right? Because there is certain things that do get absorbed across the gut, specifically in the stomach, like lipid soluble substances, like aspirin and alcohol. But another thing is it's going to decrease some of the actual secretions.

Okay. There is another exception here where it actually can. There's a sphincter muscle right here. It's actually called the pyloric sphincter. I'm not going to talk too much about it, but if you really do want to remember, what it can actually do here is it can act on the pyloric sphincter.

And when it acts on the pyloric sphincter, it can constrict the pyloric sphincter to prevent chyme from moving from the stomach into the duodenum, basically slowing down the digestive process. basically. So if you do want to remember that, it is a different one where it actually can cause Contraction of pyloric sphincter. They call this, whenever that happens, they call it the enterogastric reflex. Okay, which is basically inhibitory reflex.

It's very common and happens normally within the actual GI tract processes. But anyway, the reason why that's a little bit different is you might be like, wait, how is it causing contraction? How is it inhibiting it? Here, it's dependent upon receptors.

For example, this is alpha 1, this is usually beta 2. Okay? But again, we'll make a video on that specifically. All right, now we're going to go to the liver.

The liver, what is it going to try to do to the liver? The liver, it's mainly going to focus on trying to do a special thing here. One of the special things about the liver is that the liver can actually break down glycogen into glucose, which is important whenever our blood sugar levels need to be high so we can get our muscles contracting to be able to fight Chuck Liddell or run from Chuck Liddell, right? So what are we going to do here? The big thing here is we're going to do what's called...

Glycogenolysis. That's going to be the big thing here. We're going to want to try to cause glycogenolysis to occur for the liver. Alright, now the biliary tree here, you're not going to really want the actual gallbladder contractions to occur.

You're not going to want to be able to release bile. You're not really focusing on emulsifying fats and digesting and absorbing lipids, right? So you're going to want to try to inhibit the biliary contractions, right?

So you're going to want to be able to Decrease biliary tree contractions and flow. Here, I like that better. Let's say decrease biliary tree flow.

Okay, biliary tree flow. Because again, you're not really focusing right now on trying to be able to get rid of the bile and help to cause the emulsification of fat. That's not really your focus at that point.

Alright, again the pancreas. The pancreas, you know that there's structures here within the pancreas. They call these guys the islets of Langerhans.

And the islets of Langerhans have alpha cells and beta cells. Now, the beta cells are responsible for secreting insulin. The alpha cells are responsible for secreting glucagon.

Now, in this situation, insulin wants to be able to decrease your blood glucose levels. You don't want that. You want to increase them. So, what do you think it's going to do to the insulin production here?

It's going to focus on trying to decrease insulin production. And vice versa, I want the other hormone to even act synergistically with me to enhance the blood glucose levels. So I'm going to inhibit the beta cells but stimulate the alpha cells. So I'm going to want to try to increase glucagon production here. Okay.

All right. And there is fibers that can go to the splenic capsule here, to the spleen. Not necessarily super important to be honest with you, but it can cause the splenic capsule to have a slight contraction.

So it can go to the spleen and cause like a splenic contraction. Again, not super important in this situation. Not really significant to the fight or flight response.

Okay, so the big thing here that we were able to grasp here is that from the celiac ganglion, it's going to supply the stomach. cause the contraction of the pyloric sphincter, inhibit peristalsis, decrease absorption secretions, it's caused glycogenolysis, decreased biliary tree flow, and it's going to try to inhibit the insulin production, the glucagon production, and increase glucagon production, and again it can cause the splenic contraction of the outer capsule. Also there is, remember the celiac trunk does supply the proximal half of the duodenum, and again if you remember that it's going to decrease the absorption and the secretions of that area also.

Okay, so it's not just the stomach but also remember the proximal half of the duodenum. Alright, sweet deal. Now, the greater splanchnic nerve has another point that it goes to.

And remember, I'm telling you guys this because you have to understand that there is so much variability here. Now, there is another part here, right, that the greater splanchnic nerve can have a branch that comes off here and goes to the adrenal medulla, okay? Now, these are odd because you're going to notice here, wait, where the frick is the ganglion? In this case, there isn't really any collateral ganglion.

This is a weird exception where we say that sympathetic preganglionics are short and sympathetic postganglionics are long. This is kind of like the opposite in this case. So now the postganglionics are really short. They're actually called, in this area, they call it the chromophin cells. The chromophin cells are really important because they're acting like the postganglionic fibers.

And what happens is this is an example of what's called a Intramural ganglion. Okay, you're like, oh, I thought that was just for the parasympathetic. This is just one of the exceptions of the sympathetic. And again, as a result, it can... Act on these chromophane cells, which are very cool because they can release two different chemicals directly into the circulation.

One is called norepinephrine, and the other one is called epinephrine. Okay, and these guys can go all the way, widespread. They can have that very, very widespread diffuse effect, which is a very powerful effect, as compared to parasympathetic, which is more localized. Okay?

Alright, so that's that part. So we can go to the intramural ganglion. Okay, what else?

There's another one. The greater splenctic nerve can also give off another fiber here. And again, remember, take this with a grain of salt. It's not always the same thing.

It's not always clear cut here. But it can give off another one that goes to another ganglion. Okay? There's another ganglion here. And this guy is called the superior mesenteric ganglion.

So what are we going to have right here? We should have, let's write it here, below it, superior mesenteric ganglion. Okay, now this one's very interesting also. Superior mesenteric ganglion, remember the blood supply, superior mesenteric artery. So the actual superior mesenteric artery specifically supplied a couple different structures.

One is it can actually supply the cecum. It can supply the ascending colon. It can supply the actual transverse colon up to about around the actual left colic flexor like the proximal two-thirds. And it can also supply the duodenum, the distal half, and it can supply the jejunum and the ilium, right?

This is the easiest one to think about, honestly. If it's acting in this area, right, it's going to the duodenum. the jejunum, the ileum, the ascending colon. What do you think it's going to do?

And even the proximal two-thirds of the transverse colon. It's just going to inhibit the digestive processes. So basically, the whole result out of all of this here is it's going to basically try to, okay, we'll write this one coming down, this right here, the result of this is it's going to actually cause what?

Decrease peristalsis. What else? Decrease and the absorption because it's going to constrict the blood vessels and if it constricts the blood vessels it's not really relevant within the large intestine but it is important within the jejunum the ileum and the distal half of the duodenum but it's going to decrease the secretion processes also okay so again you can just remember decrease peristalsis decreases absorption and decreases accretion if you really want to be specific though the absorption and secretion is a little bit more important within the small intestine not as important within the the actual large intestine because they don't really play big role in absorption. They really only absorb water and electrolytes. Okay, got that guy.

And if you want there is a little information that goes to the appendix, but we're not going to talk about that. Alright, so we got the greater splanctic nerve. Now we're going to go to the next guy.

Alright, next one is going to be from T10 to T11. So this was for the greater splanctic nerve, right? This is going to be for what's called the LSN, the lesser splanctic nerve. Okay, so T10, T11, again these preganglionic fibers come out. What can they do?

They can just, they can either synapse there, become a part of the gray rima community cans, and then go into the spinal nerve and supply pylomotor, pseudomotor, vasomotor, or they can pass right through the frickers. Boom and boom. If these guys come out, what happens is, and if it does, it can go to a ganglion.

Now again, I'm gonna keep saying this because there's so much variance in these textbooks. But for the most part, this is what I was able to find is that the actual T10, T11, they come to a specific ganglion. And this ganglion is actually called the aorticorenal ganglion, right?

So we got T10, T11, which is going to pass right through. And then again, what is this nerve called? Lesser splanchnic nerve.

Okay, getting a little lazy, sorry guys. Lesser splanchnic nerve. Now that'll go to the aorticorenal ganglion. The aorticorenal ganglion will take these postganglionic fibers out. And where are they gonna go?

They're gonna go specifically to the good old kidney, right? So here let's have our kidney here, let's have the ureter, right so we're going to have this guy here. So what What I'll do is, they'll synapse here in the aortic renal ganglion and the aortic renal ganglion is going to go to the kidney and it's actually going to go to the ureter. Now, when it goes to the kidney and the ureter, what are you going to try to do?

Are you going to try to pee on Chuck Liddell? No, you don't want to pee on Chuck Liddell. That might happen, but that's not normal. But what you want to do is, is you don't want a lot of blood flow going to the kidneys and you don't really want to make urine. So, as a result, what are the two things that you would expect to happen here?

One is I'm going to decrease... Urine production, okay, that's one big thing. What's another big thing?

Well, here's a little weird thing. There's actually these things in here, in the actual kidney, we're not going to zoom in on it, but the JG cells, the juxtaglomerular cells. The juxtaglomerular cells are really important.

Why? Because what they do is they respond by beta-1 adrenergic receptors. They can release a chemical called renin and renin can set off the angiotensin 2 cascade. which can cause Adosterone, ADH, all these different hormones to get produced, which are trying to increase your blood pressure. So in that response, what else could I have?

I could have what's called renin release. Okay, but again, remember the urine production? It's usually due to what? Remember I said it's decreasing the blood flow.

So it's going to decrease the blood flow, mainly by causing vasoconstriction to the blood vessels going to the kidney, diverting that blood away from the kidney. so that we can send it to more important vital organs. That's the same thing with the stomach. Again, you're decreasing absorption and secretion, or the entire GI tract. If you're doing that, you're constricting the blood flow to it, so you can divert the blood away from those organs, so you can send it to the muscles, or the brain, or other different organs needed for you to do the flight or fright situations.

Okay? Alright, so we got that one. T12 is pretty easy also. This one's actually a little, a lot easier. It can pass right through T12.

I mean, it can go right through the chain ganglion. And again, I'm going to keep saying it. Take this with a grain of salt. There is these weird type of cells, diffuse ganglion cells.

And they're kind of like found, like they're kind of diffuse and kind of widespread around this area here. I'm going to kind of represent it like this. These diffuse ganglion cells are important because when T12, the preganglionic fibers, they can come and synapse on some of these diffuse ganglion cells.

When they do. These guys can enter into the kidney as a part of what's called the renal plexus, right? So what do we technically call this? It can synapse.

Technically, we call this the renal plexus, okay? Which again can help to support the fibers from the aortic or renal ganglion by causing random release, decreasing urine production. But again, more of it is trying to be able to decrease urine production.

Another thing that can happen with the urine production is if you don't want The actual ureter to contract, what are you going to want to do? What do you want to do to the ureter? You want to be able to decrease the peristalsis of the ureter. Okay, so that's another effect that you can get out of the renal plexus and the fibers from the aortic or renal ganglion. You're not going to want the actual ureter to be contracting.

You don't want to focus on making urine, right? All right, my darn knees. All right, so we got here T12.

I guess I should tell you what this guy's called. This is called the least splanchnic nerve. Okay?

So this fiber right here, I'm going to denote it with L. Actually, I'm going to have to write it here because that's the same thing here. This is called the least splanchnic nerve.

Okay? Okay. We are so close, guys. Alright, let's do L1 and L2 and sometimes L3. Okay, these are going to be your lumbar splanchnic nerves.

Okay, lumbar splanchnic nerves. So again, L1, you can have this guy pass through. L2, pass through. L3, pass through, right?

Now, if they pass right through, they don't go to the Chang ganglion, this is kind of important here. They can continue to keep passing through here. And here's where it gets interesting.

We're going to kind of come up over here, right? And there's going to be a ganglion over here, okay? There's going to be a ganglion right over here. We're going to kind of finish what we didn't get to over here.

So now, there's going to be a ganglion over here. where these lumbar splenic nerves can actually come to and innervate. This ganglion is called the inferior. Mesenteric ganglion. Okay, now from the inferior mesenteric ganglion, remember the inferior mesenteric arteries.

Okay, the inferior mesenteric artery. What happens with the inferior mesenteric artery? It supplies the descending colon, sigmoid colon, upper rectum, and The distal one-third of the transverse colon.

Now, what do you think you're going to try to do here? The overall result. You're going to want to try to decrease. Peristalsis. You're going to want to try to be able to, that's the main function to be honest with you, is decrease the peristalsis here.

Okay? So as a result here, the main function for this one is you're going to want to try to decrease the peristalsis. Alright, you're not going to want to try to poop or defecate in that type of situation.

That's for parasympathetic, when you're calm and you're resting, you're digesting, defecating, urinating, alright? So that's going to be for that part. Alright, so now we're going to talk about the innervation to the bladder and the interneuritis sphincter.

So we talked about how L1, L2, and L3 can go out here. Now sometimes what can happen is some even from T12, they can actually kind of come down here and so can L1 and L2. And even L3 here can actually, what happens is sometimes they can even pass down to L4. But either way, nonetheless, some of these fibers all the way down from about T12, sometimes even T11, down to about L2, L3. They can pass through, right, and they can come to an area right over here.

There's two plexi over here. One, let's actually draw it like this, there's actually two plexi over here. One is called the superior hypogastric plexus and the other one is actually going to be what's called the intermesenteric plexus. So again, L1, L2, L3 and even T12, sometimes even T11.

They can come down, right, through these actual chain ganglia, come out, and they can go to two ganglion over here. One can be called the superior hypogastric plexus, and the other one is called the intermesenteric plexus. So again, what is this one right here called?

We'll put this as the superior hypogastric ganglion. Or we can have over here this weird sucker called the intermesenteric plexus. This is actually in between, as you can hear, between the superior and inferior mesenteric arteries.

So it's kind of extending between these and allows for things to go up and go down around that area. But again, what can happen is... We're not going to talk about the things from the intermesenteric because as I said, things can go up into the superior mesenteric ganglion. They can go down into the inferior mesenteric area. So they can go and follow superior mesenteric artery or inferior mesenteric artery.

Some of them can even follow some of the actual hypogastric nerves. There's so many different areas that can come from this point. So what I'm just going to do here is I'll show that it can either go this way. It can go that way.

Some of the fibers can actually even go over here. Okay. So superior hypogastric ganglion.

gives these fibers here that can go to the internal urethral sphincter and can go to what's called the detrusor muscle. Okay, so this big, big muscle here, which is basically the muscularis externa of this bladder, is called the detrusor muscle. Alright, if you watched our video on micturition reflexes, we'll also give you a little bit more detail if you want.

But there's beta 2 and beta 3 adrenergic receptors in the detrusor muscle. Whenever it acts on that muscle, it relaxes the muscle. It inhibits it from undergoing contraction. So what is that going to do to this guy? It's going to decrease contractions.

Basically trying to prevent the process of voiding or micturition. All right, down here you have the internal urethral sphincter. Now this one's different.

Now this one actually what happened? It did not contract. Guess what's going to happen here?

The sucker is going to constrict. Prevent you from peeing your pants, right? So, or actually almost peeing your pants.

So there's actually alpha-1 adrenergic receptors in this guy, but it's going to act on this guy, the internal urethral sphincter, and actually cause constriction or contraction of the sphincter. But remember, this is the internal urethral sphincter, not the external. External is under voluntary somatic control.

All right. Now remember the superior hypogastric ganglion or plexus they call it. This one's interesting and the reason why is is it actually gives off things called hypogastric nerves.

The right hypogastric nerve and the left hypogastric nerve. And those are pretty much the main contribution into this last thing that we're going to talk about called the inferior hypogastric plexus. So I do want you to remember that the main input going down into the actual gonads, the ovaries and the testes, is going to be the contributions from the superior hypogastric plexus. The right hypogastric nerve, left hypogastric nerve, will eventually become the inferior hypogastric plexus. But before we finish that off, there's a part down here, right?

So what happens is, remember I said here, remember I said to go into the bladder, it could be from like L1, L2, L3, and it can even go out to the ganglion around L4. It can even be up to T12, T11. Well, same thing for the gonads.

The gonads can actually extend from T10 too. So T10 can actually give extensions. and so can T11.

So you can have extensions from T10, T11, L1, L2, mainly from T10 to L2. Okay, so it's pretty much going to go to about L2 here. What they do is they can come into these chain ganglia, right, and they can come out around the sacral region of these actual chain ganglia, around the sacral region.

And what happens with these guys is they're going to go and supply the gonads. Okay, so it's going to go and supply the gonads. So for that you remember that there's the uterus for the female, there's the vagina, right?

There's also some of other tissues around that area like the actual oviducts, the ovary. For the male it's going to be like the penis, the scrotum, right? So around that area there.

So this is important. So what is it going to do? Okay, for the male, what kind of effect would it have in the male?

Specifically, It's designed to initiate ejaculation. Okay? So you can remember this by parasympathetic point for the erection and sympathetic shoot for the ejaculation. And then for the female, this one, it actually is kind of interesting.

It can act on the uterus, right? And generally, it wants to cause the contractions of the uterus. So it actually can cause uterine contractions. But whenever a woman's pregnant, What happens is it switches receptors, okay, from alpha-1 to beta-2 so that the uterus doesn't contract because you don't want to pop a baby out whenever you're pregnant, right? So it can change.

So remember, uterine contractions is for non-pregnant women, but it does actually change when they're pregnant, right? It switches the receptors from alpha-1 to beta-2. But it can cause uterine contractions or ejaculation within the male.

There's also other structures called the prostate gland within the male. right, the prostate gland, the seminal vesicles, so it can actually cause those guys to produce what's called seminal fluid. All right, not as super important for these guys, but again, what is these nerves here called? These ones here, son of a gun, these are called your sacral splanchnic.

So this area here is called your sacral splanchnic nerves. And remember, this one here going to the inframesenteric ganglia and the intermesenteric plexus and the superior hypogastric. is called the lumbar splanchnix.

And remember, like I told you, superior hypogastric ganglion can give off things called right and left hypogastric nerves. So these can be what's called your hypogastric nerves. And again, the hypogastric nerves are the main contributor to...

this structure down here because what happens is the sacral splanchnics they come out to some diffuse ganglion cells out here also and what happens is the main main contributor that innervates the gonads the main one let's actually put this one in pink so that we can brighten it up here is called the inferior hypogastric plexus Okay, so the inferior hypogastric plexus is the main nerve that's going to supply the gonads, right? And it can get two contributions. Very little of it, very minute amounts, come from the sacrosplastic nerves, from like T10 to L2, but a good, good, good portion of them, the more significant contributor, is going to be from the superior hypogastric ganglion, which splits it into right hypogastric nerves and left hypogastric nerves, will eventually become...

and merge with the sacral splenctics and form what's called the inferior hypogastric plexus, which again will supply the gonads. All right, so before... Before we finish this off on the sympathetic outflow, I need to talk about one last thing I promise. And this is going to be some of the control.

So you know there's a tissue of gray matter, which is a part of the diencephalon right here. It's called the hypothalamus. There's also other structures in here. Like, for example, you can have what's called limbic nuclei. Right?

And even parts of your cortex. But here's the important thing. The sympathetic nervous system actually has contributions from the hypothalamus and it has contributions from the limbic nuclei.

In certain situations, it can even have cortical control also. So sometimes it might even have cortical control. Not very much though, but it can sometimes have some cortical control. But for the most part, the main ones is the limbic nuclei have a big effect on the sympathetic nervous system and the hypothalamus. Okay, the only reason I say cortical controls is that there's things called biofeedback techniques, where you actually can, like on your own, control your heart rate.

So there is some weird situations in which there can be cortical controls, but mainly the limbic nuclei and the hypothalamus are some of the big, big structures, tissues of gray matter within the cerebrum. that actually can contribute to innervating or stimulating the sympathetic nervous system. Because you can have these things like these presynaptic fibers that can come down and stimulate these cell bodies right here. So again, these presynaptic fibers, they can come out and stimulate these cell bodies here and activate these preganglionic motor nerves to come out and stimulate the postganglionic and go and innervate the target organ.

So remember, this sympathetic control can have a higher brain functioning control. right hypothalamus has sympathetic tissue that can actually have presynaptic fibers and come down and stimulate the cell bodies in the lateral gray horn or the intermediate lateral column and so can the limbic nuclei and in certain situations where people can have biofeedback techniques they might even have a little bit of cortical control all right all right ninja nerds i want to thank you guys so much for watching this video if you guys did watch this video if you got through the whole thing man you guys are awesome i hope you guys like this video i hope that You guys really learned something. If you did, please hit the like button, comment down in the comment section, and please subscribe.

Also, check out our Instagram, our Facebook, and our Patreon account. Please, guys, every dollar counts. It helps us to make the highest quality videos for your guys'enjoyment. All right, engineers, as always, until next time.

Transcript for:Overview of Sympathetic Nervous System

Transcript for:
Overview of Sympathetic Nervous System