hello students today we're going to talk about the autonomic nervous system chapter 15 in our book we're gonna go over some of the structural features compared it with the somatic nervous system and go over some of the physiological responses controlled by the autonomic nervous system so the somatic nervous system is the system that receives information sensory information about pain temperature basically what you could feel something called proprioception which is our brain understanding what we're doing if we're moving if our arms are moving and whatnot and all the other senses sight hearing taste smell all of that in equilibrium the effector for the somatic nervous system is skeletal muscles so any reflex that involves skeletal muscle contraction is referred to as a somatic nervous system reflex the autonomic nervous system receives sensory information from the organs in the body or any effector that we can't control consciously like the smooth muscle around blood vessels around your stomach around your intestine I know I'll put muscle there but that would be smooth muscle or cardiac muscle like in your heart and the nervous system so the autonomic nervous system is actually involved with regulating reflexes to control physiology of unconsciously perceived sensory input and we're going to talk about some of that so well the somatic nervous system structurally is set up different from the autonomic nervous system and so what we're looking at with this picture right here with a cross-section of the spinal cord the posterior root and anterior root of a spinal nerve the somatic nervous system motor output has one motor neuron with the neuron cell body embedded in the anterior gray Horn of the spinal cord if it's leaving the spinal cord going out straight to the effector which is skeletal muscle so there's only one neuron before it reaches its effector that's different for the autonomic nervous system motor output also all of these motor neurons that are part of the somatic nervous system are myelinated that's what these little sausage looking structures are around the axon and all of those neurons that innervate skeletal muscle releases acetylcholine as its neurotransmitter so acetylcholine is excited torreón skeletal muscle but we're gonna look in this chapter at the autonomic nervous system acetylcholine is not always excitatory it depends on what type of receptor or the effectors have and so the somatic nervous system has one motor neuron that leaves a central nervous system and goes straight to its effector which is skeletal muscle and at the neurotransmitter from that that neuron is always acetylcholine the autonomic nervous system is different structurally the motor output from the autonomic nervous system involves two neurons that occur in series they communicate with each other before the effector receives the signal so the first neuron that leaves the central nervous system is referred to the preganglionic neuron the preganglionic neuron always has its cell body embedded in the central nervous system somewhere and we're gonna look at where that that is the postganglionic neuron is housed in the peripheral nervous system altogether so the preganglionic neuron is always myelinated and it's neuron cell body as always embedded either in the lateral gray horn in certain regions of the spinal cord or in the nuclei of four cranial nerves and we're going to look at what those are the postganglionic neuron is always unmyelinated and it has its cell body embedded in a peripheral ganglion somewhere and then its axon then goes to the effector so you could review this little animation as are the other ones and all the other powerpoints so on this graphic we can see the examples of the two major motor outputs of the autonomic nervous system something called the sympathetic and something called the parasympathetic motor output so the sympathetic motor output occurs in two ways first both motor outputs are gonna have a pre ganglionic neuron which is the first neuron in succession its neuron has its cell body always embedded somewhere in the central nervous system if the pre ganglionic neuron has its cell body embedded in the spinal cord in different regions its cell body is always embedded in the lateral gray Horn of the spinal cord so what we're looking at here is a pre ganglionic neuron leaving the spinal cord via the anterior root of the spinal nerve and then going through the spinal nerve and terminating in something called the gang lien a ganglion is a collection of neuron cell bodies in the peripheral nervous system the neuron cell bodies that are in the ganglion if it's an autonomic ganglion is the cell body of the postganglionic neuron so here's the preganglionic neuron is the neuron that occurs before the ganglion and here's the postganglionic neuron it occurs after the ganglion the preganglionic neuron in the postganglionic neuron always make a synapse inside the ganglion so that when the preganglionic neuron fires an action potential it will dump out its neurotransmitters in a synaptic cleft and then the postganglionic neuron will send an action potential down its axon away from the ganglion to go to the effectors in the body the autonomic nervous system effectors are the organs and tissues in the body that we can't control consciously so that includes some glands the heart smooth muscle those are effectors of the autonomic nervous system and we're going to talk about adipose tissue as well but nonetheless the majority of the cases occur this way where the preganglionic neuron dumps out acetylcholine as its neurotransmitter at the ganglion and acetylcholine then binds to its receptor on the dendrites and cell body of the postganglionic neuron and in this case acetylcholine is excitatory so we're going to talk about that as well which causes the pre the postganglionic neuron to fire an action potential and when that action potential reaches the end of that postganglionic neuron it releases more epinephrine as its neurotransmitter which can be either excitatory or inhibitory on the effectors it will either increase or decrease the metabolic activity of its effectors so it's something that we have to talk about in this now there is one exception to the rules where we have a preganglionic neuron and then a postganglionic neuron before we ever get to the effector to bring about a physiological change and that exception is in the sympathetic nervous system where a preganglionic neuron leaves the spinal cord via the anterior root of a spinal nerve and terminates in the very middle of the adrenal gland so the adrenal glands lie on top of our kidneys there are two major parts to it there's an adrenal cortex on the outer part of the gland and the adrenal medulla in the middle the adrenal medulla in the middle contains cells called chromatin cells right here and when they receive acetylcholine from the preganglionic neuron in the sympathetic nervous system the chromatin cells then released epinephrine and norepinephrine into the blood so ultimately when we have a sympathetic reflex often referred to as a fight-or-flight response it involves both the nervous system controlled reflexes as well as hormonal or endocrine reflexes because the sympathetic nervous system causes the adrenal gland to release epinephrine and norepinephrine into the blood the parasympathetic nervous system always contains a pre ganglionic neuron that leaves via the anterior root of a spinal nerve if it's in the spinal cord in this case that's the picture they're showing or sometimes the parasympathetic system well the parasympathetic system has some of its its pre ganglionic neurons leaving from the brain in for cranial nerves and I'll show you that in a second so that pre ganglionic neuron then leaves and terminates in what we call a pair of sympathetic ganglion and they're the preganglionic neurons going to release acetylcholine as its neurotransmitter it's going to activate the postganglionic neuron to fire off an action potential and then the neurotransmitter released by the postganglionic neuron of the parasympathetic system is always acetylcholine so let's talk about some of these things that this these are the structural layouts for the sympathetic system and then the parasympathetic system there are going to be some questions on where are the cell bodies located for the preganglionic neuron where are the cell bodies for the postganglionic neuron located well the pictures show me exactly the layout will show you also the exact layout of where the cell bodies are located and thus where communication will occur so the ganglia always lie on the outside of the central nervous system out in the periphery somewhere and when it's a parasympathetic preganglionic neuron communicating with a Peris of postganglionic parasympathetic neuron that ganglion is referred to as a parasympathetic ganglion when it's a preganglionic neuron in the sympathetic nervous system communicating with the postganglionic neuron in the sympathetic nervous system that ganglion is referred to as a sympathetic ganglion and we're going to learn what those names are so the autonomic nervous system is divided into both sympathetic and parasympathetic nervous systems the sympathetic nervous system is also referred to the fight-or-flight division or the thoracolumbar division ultimately because the sympathetic nervous system is the system that is activated in order to keep us safe when we're under stress or in an emergency situation and so we can talk about what a fight-or-flight response is the parasympathetic nervous system is referred to as the rest and digest division or the craniosacral division and the parasympathetic nervous system is the nervous system that basically allows you to digest your food gain energy basically restore energy in the body so I put in here a table I want you to review this we're going to talk about the stuff that is in this table just for the comparison of this of the somatic nervous system and the autonomic nervous system in general some of the different features what's the sensory inputs what controls the motor output what are the motor neuron pathways so for instance in the somatic nervous system we have one neuron leaves the central nervous system he goes to the effector which is skeletal muscle in the autonomic nervous system there are usually two neurons in succession before we get to the effector there is an exception to that and that deals with the adrenal medulla that is in this picture this is the only exception to the fact that we normally have two neurons in succession this one we only have one and that's a part of the sympathetic nervous system so just review the comparisons here for each one of these categories for the somatic and autonomic nervous system now the preganglionic neuron again in real in both the sympathetic and the parasympathetic nervous system has its cell body embedded in the central nervous system it's either going to be embedded in the brain whether in for cranial nerves or somewhere in the spinal cord the postganglionic neuron has its cell body always embedded in an autonomic ganglion which exists out in the peripheral nervous system the sympathetic division or sympathetic nervous system is called the thoracolumbar division because all of the preganglionic neuron cell bodies in the sympathetic nervous system are located in the lateral gray horns from the thoracic to the lumbar region of the spinal cord I'll say that again the preganglionic neuron cell bodies in the sympathetic nervous system always have their cell body embedded in the lateral gray Horn of the thoracic to the lumbar region of the spinal cord so all of the sympathetic output from the central nervous system comes from the thoracic and the lumbar region of the spinal cord only so let's look at a picture that demonstrates that this picture has a lot of information on it and it can really tell you a lot about the sympathetic nervous system if you know what you're looking at so let me show you first off from from t1 down to l2 or l3 in that region the first view in the lumbar region the thoracic to the lumbar region of the spinal cord is where all of the cell bodies which are those little bitty dots of the preganglionic neurons are located for the sympathetic nervous system so all of these neurons that are leaving the spinal cord from the thoracic to the lumbar region are the preganglionic neurons of the sympathetic nervous system these are have nothing to do with the parasympathetic system also something else that you can notice from the picture these neurons the first neuron the preganglionic s' they the artist drew a straw a solid line that solid line means that all of those preganglionic neurons are myelinated but then if you look over here you have all these dotted blue lines that go to the different organs and tissues in the body the dotted lines are the postganglionic neurons and the dotted line represents the fact that the postganglionic neurons are always unmyelinated so the way that this works is this when the sympathetic nervous system fires and I let or sends action potentials which we're going to cover the action potential leaves via the preganglionic neuron from the thoracic to the lumbar region of the spinal cord and then that preganglionic neuron is going to make a synapse out in the periphery of the body somewhere with the cell body and dendrites of the post ganglionic neuron so what you're looking at right here on either side of the spinal cord this represents a sympathetic chain ganglion it's called the sympathetic trunk or chain ganglia ganglia pleural ganglion singular so the only neurons that communicate or synapse in the sympathetic chain or preganglionic sympathetic neurons and postganglionic sympathetic neurons there are other ganglia though that lie on the outside of the chain they lie out near large arteries in the body and I'm going to give you those names in a minute and that's what some of these other circles are that you see here so these are called pre vertebral ganglia or collateral ganglia with an older name for them and they have specific names this one is the inferior mesenteric ganglion so you'll see here that the preganglionic neuron comes out it bypasses the chain ganglion but then makes a synapse in this ganglion with the postganglionic neuron so there are two main types of ganglion for the sympathetic nervous system I'm going to give you those names in a minute so when the preganglionic neuron fires its synapses in a ganglion somewhere sympathetic ganglion somewhere in the periphery and then causes the postganglionic neuron to fire which dumps out neurotransmitters on its effector now depending on what type of receptor the effector contains the organ can increase or decrease its metabolism I'll give you an easy one right now so if the sympathetic nervous system fires to our heart so see your heart over here the preganglionic neuron is going to fire it's going to synapse with a postganglionic neuron that then goes to the heart and the sympathetic nervous system when it fires increases our heart rate that's why when you're running on a treadmill your sympathetic nervous system is firing because you're active and your heart rate goes up also the force of contraction goes up which helps increase blood flow and blood pressure in the body but nonetheless the point is is that the sympathetic nervous system when it fires to the heart it causes cardiac function to increase so the heart rate goes up and the force of contraction goes up so the heart pumps more blood out per minute which is called cardiac output but nonetheless you can see where the cell bodies are located for the preganglionic neurons always in the thoracic to the lumbar region and the postganglionic neuron cell bodies are always out in the periphery in a gangland somewhere and before the axons go to their targets or their effectors the parasympathetic nervous system has its pre ganglionic neuron cell bodies either embedded in the brain in for cranial nerves the oculomotor cranial nerve number 3 you just covered in chapter 14 the facial which is cranial nerve number 7 the glossopharyngeal nerve cranial nerve number 9 and the vagus nerve cranial nerve number 10 so here is cranial nerve number 3 number seven number nine and number ten so the nuclei in the brainstem contains preganglionic neuron cell bodies of the parasympathetic nervous system so some preganglionic neurons from the parasympathetic nervous system leave the brain in those four cranial nerves that would be the motor out for some of the parasympathetic division however there are some parasympathetic pre ganglionic neurons that have their cell body embedded in the sacral region of the spinal cord in the lateral gray horn of the sacral region of the spinal cord so since the preganglionic neurons are either leaving the brain in for cranial nerves or leave in the sacral region of the spinal cord the parasympathetic division is also called the cranial sacral division or outflow and that's why they call it that so let's look at the picture so here's the picture here's the preganglionic neurons you see their cell bodies up here embedded in the nuclei of for those four cranial nerves that was just mentioned off of the brainstem but some of the preganglionic neurons of the parasympathetic system have their cell body embedded in the lateral grey horn of the sacral region of the spinal cord so for that reason the parasympathetic nervous system is referred to as the cranial sacral division because it's pregame ionic neurons only ever leave from the brain or from the sacral region of the spinal cord so the picture definitely shows me that the other thing I can see again is that some of these red lines are solid but some of them are dotted so these solid red lines are the myelinated axons of the preganglionic neuron the dotted red lines are the unmyelinated postganglionic neurons and one other thing that we can notice from this picture - the last one which I'll pull back up is that the pretty ganglionic neurons in the parasympathetic nervous system are typically much longer and then have very short postganglionic neurons so notice on this one the preganglionic neuron is very long but that little bitty neuron right there or here or there those are the postganglionic neurons which are typically quite short because the synapse of the parasympathetic preganglionic neuron with the parasympathetic postganglionic neuron are at what's called a terminal ganglion the preganglionic neuron pretty much terminates at the organ of interest notice at the heart the preganglionic neuron comes in and then is terminating there and the postganglionic neuron is lying right on or next to the organ of interest in this case the heart so let's go back to the sympathetic system for a second typically in the sympathetic system the preganglionic neurons are shorter and the postganglionic neurons are longer so the preganglionic neurons in both divisions sympathetic and parasympathetic are myelinated in the sympathetic system the preganglionic neuron typically is shorter and the postganglionic neurons in both systems are always unmyelinated and in a sympathetic system the postganglionic neuron is typically much longer so here we can see that the preganglionic neurons are gonna leave either from the brain in these four cranial nerves that I just mentioned the ocular motor the facial glossopharyngeal and the vagus nerve or from the sacral region of the spinal cord and go to their effectors now notice here we have red lines going to each tissue and organ in the body for instance the heart let's focus on that again so you have a parasympathetic innervation to the heart and if I go back there is a sympathetic innervation to the heart so typically the organs effectors and tissues in the body have what's called the dual innervation they received both a sympathetic postganglionic neuron and a parasympathetic postganglionic neuron so what what that is all about is this the sympathetic and the parasympathetic nervous systems are innovating the same tissues there are some that don't get parasympathetic but the tissues that do get both sympathetic and parasympathetic when one of the system fires it turns the organ on and when the other system fires it turns the organ off it's not always just on and off but we can say it increases and/or decreases the metabolism of the effector or the organ for instance when you are resting your parasympathetic nervous system is firing more than the sympathetic system and so everybody knows when you're resting you have something called your low resting heart rate I'm sure you've heard of that before the reason why your heart rate is lower when you're resting relative to if you're physically active is because the parasympathetic nervous system is firing to your heart and the neurotransmitter that is released by these postganglionic neurons is acetylcholine so although acetylcholine is excitatory on skeletal muscle it makes it contract acetylcholine is inhibitory on the heart so when the parasympathetic nervous system fires the heart rate is going to go down on the other hand if you're getting up and you're going to the gym and you start moving and you're working out the sympathetic nervous system fires more often when we are either in an emergency situation or we're physically active so the sympathetic nervous system fires going to the heart for this example and it dumps out more epinephrine as its neurotransmitter and norepinephrine on the heart increases your heart rate and it increases the force of contraction so the heart can pump more blood to the muscles in the body that are working out they need more blood flow to them so the sympathetic nervous system increases cardiac function whereas the parasympathetic nervous system decreases cardiac function so that's what we call a dual innervation now there are some tissues that only receive sympathetic stimulation or I should say innervation and not parasympathetic and I'm going to mention some of those in a minute but before we do that let me talk about the ganglion and what their names are we're gonna have a couple of questions on the names of the ganglia and what is synapsing in the ganglia so in the body we always have two different types of autonomic ganglia sympathetic and or parasympathetic ganglia will do the parasympathetic ganglion first parasympathetic ganglia are called terminal ganglia because the preganglionic neuron of the parasympathetic nervous system terminates at the organ of interest so let's go back to the picture look over here for the heart again that we were just talking about the preganglionic neuron comes in and is going almost it goes all the way to the organ the effector before it ever makes a synapse with the postganglionic neuron so for that reason we call the ganglion with a parasympathetic preganglionic synapses with a parasympathetic postganglionic neuron we call that ganglion a terminal ganglion because the preganglionic neuron is terminating at the organ of interest and then making a synapse with the postganglionic neuron now the sympathetic ganglion come in two types I mentioned these already the sympathetic trunk or chain ganglion you might see that named sympathetic trunk or the sympathetic chain ganglia ganglia plural these are a pair of ganglia that lie in a whoa up and down our vertebral column just lateral to the spinal cord so let me go back to the picture of the sympathetic nervous system here is the sympathetic chain gang Lin right here all of these little nodules that you see that the artist drew in is where sympathetic pre and post ganglionic neurons can communicate and that's what a ganglion is it's where a pre and a post ganglionic neuron is communicating at least an autonomic nervous system so a ganglion by definition is a collection of neuron cell bodies out in the peripheral nervous system somewhere and since only sympathetic pre and post ganglionic neurons are communicating or synapsing in this ganglion this would be called a sympathetic ganglion so this particular ganglion which is called the sympathetic trunk or chain ganglia is where sympathetic pre and post ganglionic neurons communicate or make a synapse the other types excuse me the other types of sympathetic ganglia which lie on the outside of the trunk more towards the anterior side of the body typically by large arteries those are called pre vertebral ganglia or collaterals so the pre vertebral ganglia occur in three forms that I want you to one of the three main ones I want you to learn there's typically five or so but we're gonna learn these three main ones we covered these arteries in a mp2 as well so we have what is called a celiac ganglion a superior mesenteric ganglion and an inferior mesenteric ganglion so these ganglia are part of the sympathetic nervous system they take on the name of celiac or superior and inferior mesenteric because the gang in lies next to those arteries so there's a big artery comes off the aorta called the celiac artery really the trunk there's a superior and an inferior mesenteric artery so the ganglia that lies there takes on the same name the only neurons that synapse in the celiac superior and inferior mesenteric ganglia are sympathetic pre and post ganglionic neurons the only neurons that communicate or synapse in a terminal ganglion or parasympathetic pre and post ganglionic neurons now as far as the synapse is concerned dealing with sympathetic the sympathetic pathway there are four ways that the sympathetic pre ganglionic neuron can synapse with the postganglionic neuron so i'm going to show you these four ways off of this next picture so just read through that and then review it on this picture so let me tell you what we're looking at here first of all we're looking at a section through the spinal cord the preganglionic neuron is going to leave somewhere from the the thoracic to the lumbar region of the spinal cord since it's the sympathetic nervous system via the anterior route of a spinal nerve now the axon of that preganglionic neuron is going to enter the spinal nerve there is a connection between the spinal nerve and the sympathetic chain ganglion there's two little connectors the two little branches that connect the spinal nerve to the chain gang Lin are called the Rhema communities ray my communities there are two ray my communities an arraignments by the way is just a branch it's called communities because it communicates from the spinal nerve to the chain ganglion so the two branches are these the this more lateral branch that we see here which carry the preganglionic neuron in and here it comes that solid line means it's myelinated this branch of the RAM I community can tease is called the white ramus so you see that name here the reason why it's called the white ramus is because it's only carries myelinated neurons and that myelination appears at glistening white so that pretty ganglionic neuron can come in and join the sympathetic chain game'll in via the white ramus now here are your choices that can happen that preganglionic neuron can synapse with a post ganglionic neuron at the same level that the preganglionic neuron comes in just like this at this level of the spinal cord and then the post ganglionic neuron can leave at that same level via this branch which is called the gray ramus it's called the gray ramus because the post ganglionic neuron is unmyelinated and it's going to rejoin the spinal nerves so we have a white ramus and a gray ramus the white ramus carries the sympathetic preganglionic neuron into the chain ganglion and the gray ramus carries the unmyelinated postganglionic neuron back out now that pretty ganglionic neuron though can have branches that can go up or down the length of the sympathetic chain ganglion up and down the spinal cord and can synapse with other post ganglionic neurons at different levels up and down the spinal cord in that way we can have a broader post ganglionic neuron output motor output to multiple effectors around the body at the same time which brings about the sympathetic reflex as we call the fight-or-flight response so the second option for that preganglionic neuron is it can go up or down the sympathetic chain ganglion and CIN with a postganglionic neuron at a different level than where it entered the chain ganglion now we can also have that preganglionic neuron leave the sympathetic chain typically occurs down at the splanchnic nerves and can ultimately synapse in one of the pre verbal ganglia so notice the preganglionic neuron comes in and then it leaves and goes to another ganglion out in the body this would be called a pre vertebral ganglion that is either referred to as a celiac the superior mesenteric or the inferior mesenteric ganglion the example they're showing on the picture for demonstration purposes is the celiac ganglia in there we have a synapse with the preganglionic neuron with a post ganglionic neuron that then goes out to its effector in this case smooth muscle around the stomach excuse me then the last option that we have is for the preganglionic neuron that does not synapse with a post ganglionic neuron we have a pre ganglionic neuron that goes straight to the adrenal medulla here's the adrenal gland these lie on top of our kidneys the very middle of the adrenal gland is what produces adrenaline or epinephrine and noradrenaline or norepinephrine and the cells that do that are called chromaffin cells so we have a pre ganglionic sympathetic neuron it goes straight to the adrenal medulla so that when we have a fight-or-flight response or a sympathetic response we're intubating all of these different effectors and tissues up and down throughout the entire body along with activating the release of epinephrine norepinephrine from the adrenal medulla so for that reason a sympathetic reflex really involves the sympathetic nervous system and the in the krint system since we're causing and the release of hormones from the adrenal medulla now here's the parasympathetic motor output you can see it's a little different we have the preganglionic neuron leaves via the anterior route of a spinal nerve this would only occur in the sacral region of the spinal cord because if these neurons were leaving from the brain they would not be leaving from a spinal nerve from the spinal cord they would be leaving through cranial nerves number three seven nine and ten and in in the cranial nerves but here we have the preganglionic neuron entering the spinal nerve via the anterior root of a spinal nerve that then goes all the way to its effector smooth muscle in the urinary bladder in this example and there it terminates and communicates or synapses with the postganglionic neuron and for that reason parasympathetic ganglia are called terminal ganglia and the postganglionic neuron fires and then brings about its effect on its effector alright so please review this animation it's just the organization and overview of the nervous system and really the autonomic nervous system that we're talking about now we have to start getting into the physiology part of the autonomic nervous system which is going to involve knowing what types of neurotransmitters are being released by which neurons and which types of neurotransmitter receptors that are going to bind to those neurotransmitters so any neuron that releases acetylcholine as its neurotransmitter is referred to as a cholinergic neuron so all neurons that release acetylcholine or cholinergic all receptors that bind to acetylcholine in the body are called cholinergic receptors there are two basic types of cholinergic receptors with subtypes in there but two classes of them one major class is called a nicotinic receptor and the other major class is called a muscarinic receptor I'm going to show you where they're located in a minute but both of these types of receptors bind acetylcholine they never bind epinephrine or norepinephrine adrenergic neurons are neurons that release norepinephrine as its neurotransmitter and the receptors that bind to norepinephrine from the sympathetic system but more from epinephrine and norepinephrine from the adrenal medulla while referred to as adrenergic receptors which we have to look at what those types of receptors are so here we have some pictures that demonstrate the pre and the post ganglionic neurons in the sympathetic and the parasympathetic nervous system will do the sympathetic system first here you see a pre ganglionic neuron this cell body would always be embedded in lateral gray Horn of the thoracic to the lumbar region of the spinal cord its axon would leave and in the anterior root of a spinal nerve and then go to the ganglion in the body somewhere this sympathetic ganglion this gray circle will either be the sympathetic trunk or chain-gang Lin or it will be a pre vertebral ganglion so let's notice some things right away off the picture number one the pre ganglionic neurons are always myelinated so that's what those little sausage looking things on every single pre ganglionic neuron 100% of them without exception in both sympathetic and parasympathetic nervous systems release acetylcholine as its neurotransmitter so that means all pre ganglionic neurons in both systems are cholinergic now the postganglionic neurons in both systems sympathetic and parasympathetic always have receptors that can bind acetylcholine and as it turns out the receptors that are on the dendrites in the cell bodies of parasympathetic and sympathetic postganglionic neurons those receptors are referred to as nicotinic receptors nicotinic receptors are always excitatory those nicotinic receptors are also the ones that are located on the motor endplate of skeletal muscle that you learned about in chapter 10 and when the somatic nervous system motor neuron fires releases acetylcholine at the neuromuscular Junction it caused the skeletal muscle to contract because the receptor on the skeletal muscle was excitatory so that's the same thing here these nicotinic receptors that are on the dendrites and cell bodies of these postganglionic neurons receive acetylcholine so that when the preganglionic neuron fires acetylcholine is released it binds to the nicotinic receptors which cause the postganglionic neuron to fire an action potential and then they then release their neurotransmitter so the differences between the systems come in the form of the neurotransmitters that are being released by the postganglionic neurons because they're different in both systems so the majority of the sympathetic division has a post ganglionic neuron that releases norepinephrine there are slight exceptions to that which I'll mention in a second but I could say almost all postganglionic neurons in a sympathetic nervous system are adrenergic in other words they release norepinephrine as their neurotransmitter the effectors that they are trying to either activate or inhibit always have receptors that can bind norepinephrine and receptors that bind to norepinephrine are referred to as adrenergic receptors now the majority of the cases for the sympathetic system is the picture that you see at the top the preganglionic releases acetylcholine binds to a nicotinic receptor on the cell body and the dendrites of the postganglionic neuron the postganglionic neuron fires and releases norepinephrine on to its target where the norepinephrine will bind to an adrenal receptor about 15% of the sympathetic postganglionic neurons release acetylcholine though and almost all of these that release acetylcholine are innervating sweat glands in the body so the sweat glands in the body that are being innervated by the sympathetic nervous system like the ones on the palms of your hands and the soles of your feet those post ganglionic neurons release acetylcholine on to the sweat gland which makes them produce more perspiration when you're afraid or scared are you going through a fight-or-flight response and the effector I'm sorry the receptor on the effector that binds acetylcholine is not a nicotinic receptor they're referred to as a muscarinic receptor there's different types of muscarinic receptors some of them are excitatory and some of them are inhibitory we're not going to learn all the different subclasses of them but some activate the effector in some inhibit the effector so in this case the preganglionic neuron releases acetylcholine binds to nicotinic receptors on this dendrites in the cell body of the postganglionic neuron which makes it fire off an action potential it dumps out acetylcholine at its effector and it binds to a muscular Inuk receptor in this case these muscular Inuk receptors are excitatory and it makes us produce perspiration now the parasympathetic nervous system is all just one thing there's no exceptions like the two we see here the parasympathetic nervous system the preganglionic neuron is still all cholinergic just like all of them they release acetylcholine on the dendrites in the cell body of the postganglionic neuron and the postganglionic neuron every single one of them in the parasympathetic nervous system our cholinergic they always release acetylcholine and so acetylcholine is going to bind to a muscarinic receptor on its effector cell or organ so nicotinic receptors and muscarinic receptors bind acetylcholine only nicotinic receptors are found in autonomic ganglia where we have synapses between pre and post ganglionic neurons muscarinic receptors are always found on the effector that is going to either be activated or inhibited it depends on the exact type of receptor for instance the muscarinic receptor on your heart when the parasympathetic nervous system fires it slows your heart rate down that's because the muscarinic receptor on the heart causes the heart to decrease its function ultimately because it's a it's a ligand gated potassium channel is a receptive if you wanted to go look that up but it causes the pacemaker of the heart to be hyper polarized and thus prevents it from firing an action potential and it slows your heart rate down but nonetheless the muscular linic receptors are either excitatory or inhibitory it depends on the effector that is being innovated the adrenergic receptors come in two major forms they're referred to as alpha adrenergic receptors or beta adrenergic receptors so down here I just shorten it up and said alpha and beta so alpha adrenergic receptors or beta adrenergic receptors always bind more epinephrine they can also bind epinephrine as well that's being released by the adrenal medulla but talking about the sympathetic nervous system right now the alpha and beta receptors are located on the effectors not on the neuron so the effect is out in the body either will have muscarinic receptors or ad or alpha and beta adrenergic receptors so or both they have many a tissues contain both because they're being dual dually innovated by both systems so instead of making us memorize exactly the receptor distribution around the body I came up with some generalities to help us learn a little bit about these receptors first of all there are different subclasses of the alpha and beta receptors there's alpha ones and alpha 2 s beta 1 s beta twos there's also a beta 3 so alpha 1 and beta 1 receptors typically are excitatory that means that if an effector has an alpha 1 or a beta 1 receptor when the sympathetic nervous system fires it's going to increase the metabolism of that particular effector on the other hand some effectors have alpha twos and beta twos and these are typically inhibitory so if the effector out in the body had alpha twos or beta 2 receptors that particular effector would be inhibited beta 3 receptors only found on brown fat or brown adipose tissue and so when the sympathetic nervous system fires it basically causes the brown fat to burn lipids aerobic lee and it produces heat as a byproduct so that's called thermogenesis and babies and young children would still have brenell a lot of brown fat nodules utilize this system to increase their body temperature because babies can't regulate their body temperature very well when they're first born most adults have very little brown fat left so we don't rely on that to maintain our body temperature now also one is to learn the enzymes that break down norepinephrine and if you forgot that from chapter 12 I need you to relearn it so there are enzymes that remove the neurotransmitters from the clefts there's one called monoamine oxidase or Mao or or catecholamines for Ace or comt these two enzymes break down norepinephrine and thus renders it non-functional and it stops the reflex though the sympathetic reflex now let's go through the fight-or-flight response the fight-or-flight response occurs when you're very when you're nervous or scared or something like that or very excited so your sympathetic nervous system is turned on and it starts to fire and override the parasympathetic nervous system during what we refer to as the e situations when you're in an emergency your sympathetic nervous system is going to fire when you're embarrassed like if you have to get up in front of a class and give a speech and it kind of makes you nervous you kind of get butterflies in the stomach and the hands get cold and clammy and basically nervous that's a mild fight-or-flight response so that happens when you're embarrassed or when you're very excited or when you're exercising this is when the sympathetic nervous system fires and our sympathetic nervous system makes us use energy that's our energy system predominantly so when you're very scared or in an emergency situation you go through an alarm reaction which is referred to as a fight-or-flight that means you're either one as fast as you can flight get away from the situation or you'll fight as hard as you can to survive so some tissues in the body have to increase what they're doing and other tissues have to decrease what they're doing in order for all the energy to be focused on those essential organs to help keep you living if you're in a very very bad situation like if someone is trying to hurt you or whatnot you have to focus all of that energy in your body to the essential organs which I need to talk about some of those so we go through a fight-or-flight response your pupils will dilate the sympathetic nerdy's our sympathetic nervous system outcomes responses your pupils dialate that allows a maximal amount of light to enter your eyes so you can see what's going on better your heart rate and the force of contraction and your blood pressure that's what BP is all increase your sympathetic nervous system increases cardiac function let's face it if you need to run or fight as hard as you can you're going to have to be using your muscles and they're going to need a lot of blood flow so your heart is going to have to pump more blood to the essential organs so let's talk about that during the fight-or-flight response if you need to send more blood to the essential organs then that means you have to take blood away from an organ because you only have a set volume of blood in the body so we actually decrease blood flow to the non-essential organs and I listed a few of them out or systems really if you are let's say you're running down a dark alley someone's trying to hurt you or you know God forbid kill you then you don't have to digest your a hamburger that you might have eaten for lunch so the digestive system organs are non-essential at that moment you don't need them to live if you're about to die immediately your reproductive structures in organs their non-essential your kidneys in parts of the other parts of the renal system or not all that important at that moment obviously everything in our body is important but not at that moment so we have to decrease blood flow to these types of organs and tissues so how do we do that well you do that through vasoconstriction and vasodilation basal constriction is when the diameter of a blood vessel decreases basal dilation is when the diameter of a blood vessel increases so if you want to decrease blood flow to a tissue you can constrict the blood vessels off at that tissue and if you want to increase blood flow to a tissue you can dilate the blood vessel so more blood volume can get through the blood vessel so how do we constrict or dilate the blood vessel then well there is smooth muscle around the blood vessels in the body and if the sympathetic nervous system fires and the tissues blood vessels smooth muscle has alpha 1 or beta 1 receptors typically alpha ones then which are excitatory the smooth muscle will contract and it clamps the blood vessel off if the tissues have alpha twos or beta 2 receptors which are typically inhibitory mainly beta twos for the for the smooth muscle then the smooth muscle relaxants and the blood vessel dilates so without memorizing where alpha ones and and beta tubes are located and whatnot we can infer something here the non-essential organs need to have blood taken away from them we need a decrease blood flow to them so we can send that blood to the essential organs so all of the tissues and organs in your digestive system reproductive system and renal system have alpha ones and beta ones the blood vessels so that when the sympathetic nervous system fires those blood vessels constrict brings about basal constriction which decreases blood flow to them the essential organs in our body include well and right all of them down but skeletal muscle cardiac muscle your liver your brain and your lungs let me tell you why your brain needs more blood flowing to it because you have to think very clearly your lungs name more blood flowing to it so they can oxygenate more of blood because your muscles are in your heart and other tissues are about to work a lot and they need more oxygen to make ATP your skeletal muscles are the ones that are contracting to either make you run or fight so they need more blood going to them so they're essential and then the heart itself obviously is important because it's just the effector that is pushing blood through the body now the reason why your liver is important is because your liver stores sugar and during a fight-or-flight response a sympathetic event your blood sugar levels go up a little bit in your blood and the reason for that is because the sympathetic nervous system activates the liver to release sugar into the blood really via two things will learn we'll learn more of this later but it's called glycogenolysis and gluconeogenesis those two events in the liver increase with the sympathetic response which increases our blood sugar so we need more blood sugar because the skeletal muscles are trying to use as much energy as possible so they can contract more efficiently so these are what I would call the essential organs to keep you healthy in an emergency situation your brain your lungs skeletal muscle cardiac muscle and your liver now a sympathetic response also causes a bronchodilation this is a increase in a diameter of your airway so it's easier to breathe so it increases a diameter of the airway called bronchodilation and your sympathetic nervous system increases your respiratory rate so you can oxygenate the blood more efficiently so and I've already said that your blood glucose level will increase that's mainly due from the liver not the only thing but mainly from the liver all right so that's a sympathetic response so make sure you review that I think they have some pretty good tables in your book that I might have left out of this PowerPoint but just review the responses for the fight-or-flight response now let's talk about the parasympathetic system with its receptors so the parasympathetic nervous system again is all cold energic the preganglionic neuron releases acetylcholine the postganglionic neuron releases acetylcholine and so they're both cold and urging nicotinic receptors are always found on a dendrites in the cell body of a post ganglionic neuron only muscarinic receptors are always found on the effectors out in the body so we have to know that distribution nicotinic receptors are found on the postganglionic neurons but the muscarinic receptors are found on the effectors now both the nicotinic receptors and the muscarinic receptors can bind acetylcholine the reason why they're called nicotinic or muscarinic as this nicotinic receptors can also bind nicotine so they're called nicotinic muscarinic receptors are called muscarinic because those receptors can bind a to a mushroom poison called muscarine and as it turns out muscarinic receptors can bind to Musker in but it can't bind nicotine nicotinic receptors can bind nicotine but it can't bind to mustering but what's kind of interesting is that both of these receptors can bind to acetylcholine and I won't go into details about why that is but both of those receptors bind acetylcholine the nicotinic receptor is also the type of receptor that's located at the neuromuscular Junction however this is part of the somatic nervous system not the autonomic nervous system but that same type of receptor is excitatory on skeletal muscle alright so let's go over the parasympathetic responses now the parasympathetic nervous system called the rest and digest system is the part of the motor output of the autonomic nervous system that overrides most of the day so most of the day our parasympathetic nervous system is firing your sympathetic nervous sporadically fires over the parasympathetic nervous system depending on what you're doing if you're lying on the couch all day long and you're not moving your parasympathetic nervous system is the one that's firing but the minute you start to get up and walk around or become physically active or if you get very nervous or you're in one of those emergency situations the parasympathetic nervous system stops firing and the sympathetic nervous system fires to bring about the sympathetic reflex or fight or flight response now let's go over the five major responses of the parasympathetic nervous system right so parasympathetic nervous system is going to be firing when we're resting it allows us to digest our food and it makes our body restore its energy conserve and restore energy in our body now the acronym sludd stands for salivation lacrimation urination digestion and defecation these are the four major activations or increases of the parasympathetic nervous system for instance when we get hungry we start to salivate produce saliva you know you part of the digestive system reflexes that we'll learn later but nonetheless we increased salivation with the parasympathetic nervous system you increase tier of production tears that's called lacrimation if you've never heard of that lacrimation is a production of tears so that increases with the parasympathetic nervous system urination going in the bathroom digesting your food and defecation going in the bathroom all of those are activated by the parasympathetic nervous system there are three important decreases that is a that occurs because of the parasympathetic nervous system though when the parasympathetic nervous system fires it decreases your heart rate so that's why we have a low resting heart rate rate when we're resting because a parasympathetic nervous system is dumping out acetylcholine on to our pacemaker and the muscarinic receptor on the pacemaker is a ligand gated potassium channel which is inhibitory so it inhibits the pacemaker and your heart rate goes down the diameter of your Airways go down that's called bronchoconstriction so our parasympathetic nervous system decreases some of the bronchial tubes a little bit through what we call bronchoconstriction we also decrease the diameter of our pupil so your pupil constricts down and get smaller with parasympathetic output but it actually dilates and gets bigger with sympathetic output so those are the main reflexes of the parasympathetic nervous system that I want you to make sure you kind of understand and the last thing I put down here something called paradoxical fear a paradoxical fear event is a fear event where someone thinks that they are definitely going to die there's no escape from their stress or whatever they're going through if someone's trying to hurt them and whatnot and so I don't know if you ever seen like in a movie I've heard that people lose control of their bowels when they get really real nervous or real real real scared that is a paradoxical fear event so when they're very very very very scared the scared is that they could ever be which is subjective what scares one person doesn't scare someone else but nonetheless something that is very very fearful to somebody could cause a massive activation of the parasympathetic nervous system that then causes urination because it activates urination and defecation so the people go to the bathroom when themselves when they are very very very frightened remember normally when you're very scared you're going through a fight-or-flight response which is a sympathetic event the sympathetic nervous system decreases digestive function decreases renal function all of that so you're not going to go to the bathroom and yourself because of the simple that nervous system you're going to go to the bathroom on yourself because of the parasympathetic nervous system firing all right so with that I put in a table that compares the sympathetic nervous system and you see thoracolumbar division with the parasympathetic nervous system or cranial sacral division so I want you to make sure you go through each one of these categories and compare the distinction between sympathetic and parasympathetic so it's got some really good information in one place on this table and that's why I put it in there alright so if you have any questions just email me and I'll get back to you please review the video a few times before we talk about it all right thanks