Neurology | Autonomic Nervous System

I ninja nerds in this video we're going to talk about the autonomic nervous system so the autonomic nervous system is extremely extremely important okay so what we're gonna do is before we even start getting into the nitty-gritty parasympathetic and sympathetic and enteric I want to talk about what exactly the branches are that actually make up the autonomic nervous system so for example if we come over here real quick when we talk about the divisions of the nervous system you know there's the central nervous system which is the brain and the spinal cord and then there's

the peripheral nervous system the peripheral nervous system is broken into two systems right a sensory system and a motor system alright the motor system what we can do is is we can actually break that into two parts one it's called somatic motor which is a part of your somatic nervous system okay and this one is under voluntary control in other words if I want to have my biceps break I contract I have voluntary control over that right so we call that stomata motor where is my heart or my GI tract or other different parts of

my actual viscera those aren't under voluntary control thank goodness they're not they're under involuntary control so the involuntary control is a part of your visceral motor they call this the Auto Nam ik nervous system okay the autonomic nervous system which means it stands by itself okay now the autonomic nervous system there's three traditional branches of it okay most people know it by the sympathetic nervous system the parasympathetic nervous system and the last one most people don't consider it they forget about this one but the enteric nervous system the enteric nervous system is another branch will

have a specific video focusing on this in the GI physiology but for right now we're gonna focus primarily on the sympathetic nervous system in the parasympathetic nervous system in this video okay all right so let's go ahead and talk about the differences real quick between the autonomic nervous system and the somatic nervous I'm just very very briefly all right so somatic nervous system one of the big big differences when we're talking about this is this guy the somatic motor fibers it takes one motor neuron to reach its effect your effector organ so this right here

is going to be representing the somatic nervous system so what do I mean you see this motor neuron right here they call this an alpha motor neuron it only takes one of these motor neurons to extend all the way from the spinal cord you know what part of the spinal cord specifically it's in with the anterior gray Horn of the spinal cord okay so the anterior or ventral gray Horn of the spinal cord this alpha motor neuron comes out and this alpha motor neuron will come to an effect or work and usually your skeletal muscles

and it will release a specific chemical that acts on this effector tissue do you know what that chemical is called it's called acetylcholine okay an acetylcholine whenever it's released on this target tissue will act on specific receptors that we'll talk about in other videos which is going to be called a nicotinic receptor alright nicotinic M receptors for muscular system so they're going to cause the contraction of that actual skeletal muscle now differentiating the somatic versus the autonomic we have to remember that the autonomic nervous system and again we're only specifically in this video talking about

the sympathetic and the parasympathetic okay the autonomic nervous system takes two motor neurons to reach their effector organ okay we call the first one the first one which is coming out from the spinal cord or coming from the brainstem because you have cranial nerves that actually actually act as automatic automatic nerves this first one is called a pre ganglionic and this next one afterwards is going to be called a post ganglionic motor neuron but we just want to for right now we're not going to go into the big big differences here I just want us

to understand that the preganglionic motor neurons are gonna be the ones that are coming out of the spinal cord or they're going to be coming from the actual brainstem the postganglionic motor neurons are usually going to be going to the effect organ and we'll talk about specific ganglia afterwards not right now okay so now we have the basic difference between the somatic nervous system and the autonomic big difference is one motor neuron to reach the effector organ autonomic takes two motor neurons to reach the effector organ first one is the preganglionic the next one is

the postganglionic we'll go into more detail on these after let's go ahead first and focus on the sympathetic then we'll talk about the parasympathetic okay so the sympathetic nervous system what is it for what's its purpose you probably might have heard it is a the fight or flight or fright stage right it's designed to be able to use energy it's used in stressful situations right or in many different types of situations I like to think about it is like you're running away from some dangerous animal like an orangutan alright what's gonna happen we'll talk about

that in the individual video but for right now we need an intro of where you're gonna find the sympathetic nervous system within the spinal cord so this is a specific part of the spinal cord and it extends all the way down from t1 from your t1 vertebrae down to about l2 this is the part of the spinal cord from t1 all the way down to l2 there's a specific portion and this portion is primarily where the preganglionic cell bodies of the autonomic nervous system specifically the sympathetic are found and we'll talk about where exactly after

but from t1 to l2 they call this the thoracolumbar outflow okay because this is where the sympathetic nervous systems coming out this is where the preganglionic cell bodies are located right here within the t1 to l2 region and they're gonna come out and they can go to different ganglia and we'll talk about all that stuff afterwards because we're going to talk about each different type of splanchnic nerve in an individual video on the thoracic on the sympathetic nervous system okay because these guys will go to a post ganglionic motor neuron and that'll go to the

effector tissue okay but we'll talk about this afterwards but I just want you to get the basic difference here is that the thoracolumbar outflow is gonna be for the sympathetic nervous system from t1 to l2 now the parasympathetic nervous system where would you find that one exactly the parasympathetic has different parts within the spinal cord one part is you're gonna have to remember it's within the brainstem you know within the brainstem you have the third cranial nerve oculomotor nerve well there's parasympathetic fibers that move with the third cranial nerve and it starts here at this

nucleus called the edding or Westfall nucleus and it comes out here and supply specific structures that we'll talk about individually in the parasympathetic videos but it'll come to some type of ganglion which we'll talk about and this is mainly gonna go and supply parts of the eye all right but remember what nerve is this this is cranial nerve three it moves with and this is going to be parasympathetic fibers so cranial nerve three has parasympathetic input okay what else you know here this blue nucleus they call this the superior salavat or nucleus the superior Salvatori

nucleus is going to be where the preganglionic cell bodies are found and they're gonna come out here as a part of a specific nerve and it's just called the facial nerve or cranial nerve seven so cranial nerve seven is actually going to have parasympathetic outflow and it'll go to many different structures we're not going to talk about those target tissues now what else another one is going to be right here the inferior salivatory nucleus that's going to be for the glossopharyngeal nerve so the glossopharyngeal nerve is what nerve this is going to be cranial nerve

nine and this is going to go to specific tissues also and what's the last one within the brainstem son-of-a-gun the last one within the brainstem is going to be the vagus and this is that big Mambo Jambo this guy goes to so many different tissues if you haven't watched them already we've already made videos that go into super super detail on all the branches of cranial nerve 3 7 9 and 10 I suggest you guys watch those because we're not going to go into a whole bunch of detail in these videos okay but this is

going to be cranial nerve 10 the vagus nerve and it goes into specific tissues so we know cranial nerve three seven nine and ten our parasympathetic nerves what else down here down here within the sacral region of the spinal cord now there is controversy in some textbooks they say it's within the lateral horn in the spinal cord they don't really say that it's there there is books that will say that there is technically no lateral gray Horn of the spinal cord within the sacral region but for right now we're just going to say that it

is within the lateral part of the spinal cord but specifically what part what level of the spinal cord specifically around s 2 s 3 and s 4 this is one heck of an ugly s let me fix that so s 2 s 3 and s 4 this is going to be for our pelvic the pelvic splanchnic serves we'll talk about that ok but these are going to be going to a bunch of target tissues also so what we know is is that the parasympathetic is made up of two portions the cranial nerves 3 7 9

and 10 and the sacral region s 2 s 3 S 4 so what do we call that we call this cranial sacral outflow okay so what are we gonna put it up here here here here alright so it's gonna be called the cranial sacral outflow okay and this is again made up of cranial nerves 3 7 9 10 and s 2-4 okay this is the cranial sacral outflow alright so we know what levels of the spinal cord you're gonna be seeing this coming from thoracolumbar t1 l2 sympathetic parasympathetic granular 3 7 9 10 s2 s4

ok so we covered that we know what regions of the spinal cord and brain stem what I want to do now is I want to zoom in on this thing that we talked about the ganglia all right so now if we come down here I want to talk a little bit more about these autonomic neurons ok I know we talked about pre ganglionic and post ganglionic but I want to get a little bit more into that so now let's say that this top one up here this one here this nice blue color this is going

to be our baby blue this is the sympathetic nervous system we're going to represent this one now there's structural differences between the parasympathetic and the sympathetic nervous system they're certain their axons their neurons the ones that are coming out of the spinal cord this pre ganglionic they're very short okay so these pre ganglionic motor neurons within the sympathetic nervous system they are short okay these ones over here the postganglionic that we already termed and the sympathetic nervous system they're going to be long so they're short in the pre ganglionic and long in the postganglionic okay

but in the parasympathetic nervous system here in this darker blue these are the pre ganglionic so we already know that it's just flipped so now the pre ganglionic motor neurons are long and the postganglionic motor neurons are short okay there's a reason why for this so parasympathetic nervous system these long pre ganglionic motor neurons they travel and travel and travel until they reach very very close a target organ sometimes even within the target organ so when we talk about these ganglia first off how do we define a ganglia a ganglia is just a group of

cell bodies that are located within the peripheral nervous system that's all they are so if you look I'm only drawing one of these cell bodies but there's multiple of them okay multiple cell bodies within that ganglia it's just a group of them now there's only one specific type of ganglia in the parasympathetic nervous system because these preganglionic sar so long they pretty much reach their effect organs sometimes they go in there affect organ so they call that terminal so they sometimes refer to this one as a terminal sometimes you might even hear another synonym a

terminal or you might even hear the word intra mural ganglion okay so for the parasympathetic nervous system you're going to hear two different terms one is you could find what's called a terminal ganglion or you can find an intramural ganglia it just means that they're either at the target organ or inside of the target organ that's why these have to be long now for the sympathetic it's a lot more complicated unfortunately these you have so many different types of ganglia and that's what we're gonna go ahead and talk about now because there is so many

of these okay but before we do that actually let's actually say one more thing about these preganglionic and postganglionic interaction when we look at the sympathetic I want to zoom in real quick on that synapse just zoom in real quick on it so let's say that I zoom in on this and I look at here's the axon terminal and here's the cell body of this postganglionic motor neuron I want to know what type of chemical is being released here at this ganglion this presynaptic the postsynaptic interaction generally this chemical that's going to be released is

going to be acetylcholine and acetylcholine will come over and stimulate this postganglionic motor neuron okay so therefore we call this fiber the preganglionic parasympathetic the sympathetic fibers we call these cholinergic fibers because they're releasing acetylcholine then if i zoom in here I look at the actual effector tissue so now the possi angling ionic motor neurons are gonna release a specific neurotransmitter onto their target tissue what's that chemical that they release it's not acetylcholine instead it's called neuro epinephrine so norepinephrine is released which will act on the target tissue so pre ganglionic sympathetic release acetylcholine so

they're cholinergic postganglionic sympathetic released norepinephrine so they're referred to as adrenergic neurons okay now parasympathetic if we zoom in on that synapse there if we zoom in on this synapse it's the exact same as the sympathetic preganglionic so here's the axon terminal here's the cell body when they release a chemical they release acetylcholine an acetylcholine stimulates this postganglionic motor neuron to fire if we zoom in on this one here the postganglionic motor neuron to the target tissue it still releases the same thing acetylcholine so how would we define this we would say that the preganglionic

sympathetic neurons are cholinergic the sympathetic postganglionic neurons are adrenergic the parasympathetic preganglionic motor neurons are cholinergic and the parasympathetic postganglionic motor neurons are cholinergic okay so cholinergic cholinergic cholinergic adrenergic now that we've done that let's go ahead and zoom in now on the different types of sympathetic ganglia all right here's a nice big beast of a diagram here right so we have to talk about the different types of ganglia within the sympathetic nervous system okay before we do that I want to talk about where you're gonna find these cell bodies of those preganglionic motor neurons

so we have a cross-section of a spinal cord right within the cross section you have the anterior gray horn or the ventral gray horn and you have the post your gray horse or the dorsal gray or within the thoracolumbar region member t1 to l2 you have an intermediate lateral gray horn okay an intermediate lateral gray horn and right here is where you're going to find the cell bodies of the preganglionic sympathetic motor neurons so for example here let's say i zoom in on this guy that cell body is the preganglionic step of that ik motor

neuron it can come out here right so we know here's the preganglionic it can move out through that with along with the somatic fibers from the anterior horn and it can move through the ventral root when it goes to the ventral root it can go out into the ventral ramus where the spinal nerves are eventually form right but there's something really cool here what can happen is these preganglionic sympathetic motor neurons can actually move in to this little like little sac of cell bodies here it can move into this little like sack of cell bodies

what do they call that wonder there's a group of cell bodies and the pns it's a ganglia so there's gonna be a whole bunch of cell bodies here so it's called a ganglia but what is this one here that's a ganglia oh what's this one down here that's a ganglia what's this one up there that's a ganglia all the ganglia are connected in like a chain so what do you think they call these ganglia they call them Chang ganglia so this ganglia right here is specifically called there's many names for these sons of guns you

can call this one a para vertebral you can also call them if you don't want to call them pair of vertebral you can also call them a chain ganglia so you can call them pair of vertebral ganglia or you can call them the chain ganglia so whichever one you guys prefer but again these preganglionic sympathetic motor neurons are coming out through the ventral root all right and then as they do that they go into the ventral ramus they come through to this chain ganglia but how what's this little tube right here called that they move

into it through it's actually you know these pre ganglionic motor neurons are very very myelinated so because they're very very very myelinated they show up as a white matter okay so this is when you look at this it's gonna look like a lot of white matter so they call this the white ray my community cans okay the white ray might communicants now that's just the actual pre ganglionic sympathetic motor neurons their axons myelinated comes into this chain ganglia where there's gonna be a whole bunch of cell bodies let's just draw a bunch of cell bodies

in here actually she's-- draw one for the heck of it there's going to be the cell bodies of the postganglionic motor neurons now from here we're gonna go through the 3 3 scenarios of where they can go right if it comes here synapse is on that cell body that post ganglionic motor neuron that cell body and when it does it axes it exits out through this next little tube it goes out through this other tube and then through the ventral Ram is with the spinal nerve so it goes with the ventral ramus as a part

of the spinal nerve and goes to three different types of locations okay if it does that tube right there this one here is called the gray ray my communicants now the question is why is it gray it's because it's not myelinated so if it's not myelinated it's gonna they're not gonna have that myelin sheath so that's why they call it gray ray might communicate because it's unmyelinated axons so now if this preganglionic goes through the white ray of my community can synapses on the cell bodies in this chang ganglia or paravertebral ganglia goes out through

the grey ram i communique as it enters into this venture ramus with a spinal nerve this is going to go to three different types of tissues okay so now if it comes out and goes to this action smooth muscle tissue that's actually found within the skin and it can contract and pull our hairs up it's called the erect or Li muscle so these fibers are called pilo motor fibers because it's going to the erector pili throughout our entire body throughout the entire level of the thoracolumbar output okay it can also go to other different regions

it can go to the actual blood vessels so we can actually go to our blood vessels and cause the vasoconstriction of our blood vessels so if that's the case they call this vasomotor fibers so I can go to our blood vessels which are gonna be called vasomotor fibers or it could go to certain glands like sweat glands throughout our entire body so they call that pseudo motor okay so we can go to sweat glands and this is one of the I didn't mention it over there but there is a couple exceptions to the sympathetic postganglionic

motor neurons one of them is that sweat glands the postganglionic sympathetic they don't release norepinephrine they actually release acetylcholine which is one of the exceptions there's many exceptions but this is one of them okay they'll talk about another one which is actually it doesn't actually act as a chain ganglia doesn't act as a collateral ganglia it actually goes straight to the adrenal medulla which is actually gonna be an example of an intramural ganglia we'll talk about it as one more exception okay so one type of ganglia is the Chang ganglia or the pair of vertebral

ganglia they go through the white out through the gray and they go a part of a spinal nerve to the pilo motor fibers vasomotor fibers or pseudo motor fibers okay what's the next example let's say that we take again what is this over here our intermedia lateral gray column right here and again what are we gonna have here we're gonna have two cell bodies of the preganglionic sympathetic motor neurons they can come out again these fibers are gonna still going to be the same they're going to come out through the ventral root when they go

out through the ventral root the only thing it's gonna be a little different is they're still gonna go through the white ray my communicants they're still going to go through this white ray my communicants and they can go in here and two things can happen right so let's say that it decides that these fibers when they come in it decides you know what I'm not gonna actually go through the gray rain light communicants I want to go down to another level so guess what it does it says you know what I'm gonna take and just

go down another level of the spinal cord so it decides to descend down and that crazy so I can descend down as it descends down it goes into another ganglia it didn't synapse here it just goes straight through the chain ganglia and down to a level below that part of the spinal cord when it does that it then can go to an actual chain ganglia and then it goes to this chain ganglia it can synapse and then what can happen here is it can actually still move out through the gray array my community cans and

become a part of the spinal nerve right and then go to the erect or peel I again the the pile of motor vasomotor or pseudo motor or you know what else can happen it can actually directly leave on its own it doesn't even have to become a part of the spinal nerve it just leaves it's its own nerve you know what they call that when things leave as their own nerve it doesn't even go through any type of nerve part it goes through its own this right here is called a splanchnic splanchnic nerve okay so

what have we seen here if they can go through the white where in my community cans to a Chang ganglia at that same level then what can happen is it can go a level down go to their synapse on these cell bodies and maybe go out through the gray or in my community cans and go to PI low motor sudo motor vasomotor or it can synapse on the cell bodies there these postganglionic motor neurons and come out as its own nerve that is called a splanchnic nerve there's going to be a good example of the

ones in a thoracic viscera that go to the heart the lungs in the esophagus okay following off at this blank Ticknor so I mean you might be like oh I thought splain ignores have to go to a collateral ganglia they do but those are the ones that are going to more of your abdominal viscera so for example let's say I take these fibers here they come through the white rain my communicants they go into the Chang ganglia they don't synapse they're just like the ones that went down instead they say you know what I'm gonna

go through this alternate tunnel I'm gonna go down through this alternate tunnel here and I'm gonna come here to this ganglia that's located in front of the vertebral column even in front of that actually right around the aorta so they actually call these ones because they're in front of the aorta they're in front of the vertebral column there's so many names for these son of the guns if you would look at these ones let's write down all the different types they can call them pre-k or Duke you know what else they can call them pre

vertebral they can even call these guys collateral ganglia and then for the last one you can even call them because they're beneath the diaphragm they're going to a lot of the abdominal pelvic viscera they're called sub diaphragmatic ganglia ain't that crazy so there's so many names for all of these darn ganglia here ok so these are going to be the ganglia of the autonomic nervous system that are going to be going to a lot of your abdominal pelvic viscera the splanchnic nerves down there those are the ones that are going down to the full racks

so if it does do this if it does synapse here it can actually go through its own little nerve again this little nerve that's coming from the collateral ganglia and going on its own this is a splanchnic nerve but it's the splanchnic nerves that are supplying the abdominal viscera area so this is still a splanchnic nerve and we'll talk about the thoracic the lumbar and the sacral endings in the sympathetic videos ok so what do we have so far we have ones that can go out at the level we can have ones that descend at

a level we have them either go if they go down a level they can go through the gray Rama or they can come out as their own blanket nerve we have ones that can actually pass right through the Chang ganglia and go to a collateral a pre vertebral a pre or DIC a sub diaphragmatic and go in their own nerve called a splanchnic nerve what else well if it can go down it can go up alright so guess what these fibers let's say that we take here this one was at this level here it went

down let's say it goes up so if it goes up it can go in ascend to a level and then from that level it could either synapse on the cell bodies here it might even go up another level - sometimes you can go up more than one level but it can ascend and let's say that it ascends to this level here and it synapses on cell bodies right in this area what can happen it could either go out as its own spike Nick nurse it could either do what go here out through the gray Ram

light communicants and become a part of the pylon motor pseudo motor vasomotor fibers so many different things that can happen here okay so what we know about the sympathetic ganglia is we have paravertebral or chain they're the same thing they're these trunks basically all the way up and down and this can allow for them to ascend descend or go out at the same level pria aortic pre vertebral collateral sub diaphragmatic means that they go through the Y tre my communicants they pass straight through the Chang ganglia and go to another ganglia these collateral preordered subdiaphragmatic

or pre vertebral and then go out as their own splanchnic nerve and then the last exception was the one that supplies the thorax which is going to be for acts and even some parts of the head in the neck is it can actually come through the Y train my communicants right like if it happened at this level I didn't show it here but it could - so for example if I come down here to this last part let's say here is the intermediate lateral grey column it comes over here comes out through the ventral route

through the ventral ramus comes through the Y train like community cans and synapses on the cell bodies here the cell bodies could either go out at that level or they could come as their own splanchnic nerve all right so I think that pretty much explains what we need to know about the chain ganglia okay guys so I hope you guys enjoyed this video on the intro to the autonomic nervous system what we're going to in our next couple videos is we're gonna talk a little bit more in detail on the cranial sacral flow talking a

little bit more about those ganglia and muscarinic and nicotinic receptors and then we'll have one more video which is going to focus on a little bit more detail on the sympathetic nervous system talking about those splanchnic nerves the different gangland a little bit more detail and then talking about the adrenergic receptors okay alright engineers till next time