Neurology | Cholinergic Receptors

I know engineers in this video we are gonna talk about cholinergic receptors these are extremely important because they are specifically for the parasympathetic nervous system okay so cholinergic receptors they fall under two different types of categories and that's what we're gonna talk about in this video one is called nicotinic okay so here let's let's write this down here let's say we have two different types of cholinergic what does that mean to be cholinergic cholinergic receptors I'm gonna put R here means that these receptors will respond to acetylcholine that's it that's all it is it just means that these receptors are responding to a seal coaling there's two different types here so if I have here cholinergic receptors there's one type which are called Neko ten ik receptors now nicotinic receptors they respond to acetylcholine but they also respond to something that can act as an agonist to that in other words an agonist is just saying it can exert the same effects nicotinic receptors respond to acetylcholine and nicotine okay that is the agonist here but there is two different types of nicotinic receptors in actuality one is we denote it as in in okay this is the nicotinic receptors which are on neurons okay these are the nicotinic receptors that are present on neurons and we'll talk about these and there's another one which are called in M and these are the nicotinic receptors which are present at the actual neuromuscular Junction on the muscle cells specifically the skeletal muscles so again the nicotinic receptors that are present on the neurons are present in like two basic locations right one is they're gonna be found at the ganglia and autonomic ganglia so they can be found at what's called Auto Nam ik ganglia so you know whenever you have for example this is a perfect example we said autonomic ganglia this right here is the ganglia a ganglia is a group of cell bodies that are located within the peripheral nervous system there's two types though right we have pre ganglionic motor neurons that four parasympathetic and pre ganglionic motor nerves that are going to go to the sympathetic ganglia but either way these nicotinic receptors are present on the actual ganglia so for example if I had let's say I have one like this here is going to be a presynaptic neuron and it's going to release acetylcholine that acetylcholine is going to bind onto a post ganglionic motor neuron which is going to go out and perform some specific function maybe it might release acetylcholine if it's a parasympathetic post ganglionic or it might release norepinephrine if it's a sympathetic postganglionic but these receptors that are present on the cell body here those are the nicotinic receptors that are present on the autonomic ganglia so we can denote that as in in there also present in so many other places within the central nervous system they can be found in so many different areas of the central nervous system so we can find this in the central nervous system in so many places okay that is the significance here and again we said that the nicotinic receptors that are present on the actual neuromuscular Junction are specific to skeletal muscles these are specific only to skeletal muscles that are present at the neuromuscular Junction okay now we're going to talk about these before we do that I want to talk about another group of cholinergic receptors so I'm going to talk about the next group and then after that we'll dive into the nicotinic and then we'll dive into the next one okay the other a subtype of cholinergic receptors is of the category muscarinic receptors so now the next one is called muscarinic receptors now muscarinic receptors means that they can respond not only to acetylcholine but they can respond to a chemical called muscarine so muscarine can also act as an agonist in other words that exerts the same effects as Sheila : on these receptors and there are so many different types of muscarinic receptors there's actually five types so m1 m2 m3 m4 and m5 we are gonna mainly mainly focus in this video on M 1 2 m3 because these are the most relevant to this discussion m4 and m5 they're also not found in too many locations they're specifically found within the central nervous system ok but we're gonna talk primarily about M 1 M 2 and M 3 ok now the next thing I want to talk about is we know that this is how we can we can classify these due to different types of receptors but and the next thing is we should define them in another way nicotinic receptors are what we refer to as Metabo I'm sorry I I on channels these are ion channels but these ion channels are ligand gated so we can actually even add on to this definition of nicotinic receptors and we can say that these ion channels are ligand gated ion channels okay so nicotinic receptors that are present on the autonomic ganglia central nervous system or skeletal muscle cells are going to be ligand gated or chemically gated ion channels and I'll explain that whereas muscarinic receptors are primarily what we refer to as g-protein coupled receptors ok these are also called serpentine receptors that means that they pass through the membrane like a snake a total of seven times so these are really really important ok so now that we understand there's two different types of cholinergic receptors we understand how these receptors are structurally and functionally different now let's talk about the mechanisms by which these receptors function okay so first things first let's talk really briefly about the nicotinic receptors present on the autonomic ganglia and on the central nervous system okay so let me zoom back in to this diagram that we just had here a second ago so let's do this right here let's say here I'm going to have a presynaptic neuron so here's my presynaptic neuron this one right here off of that I'm gonna have another one and this guy right here is going to be my postsynaptic neuron so this is my postsynaptic neuron what happens is is we have these nicotinic receptors that are present on the actual postsynaptic membrane okay of this postsynaptic neuron let's do these guys in this baby blue color so look here's going to be this receptor and these receptors are so darn cool let's pretend for a second this this channel this actual ion channel has closed there's like a little gate right up above them right there's a gate right up above them but then there's a little pocket kind of like a seesaw if you will here's like a little pocket like a seesaw what happens is these presynaptic neurons they can release a chemical from these autonomic ganglia called acetyl choline right and what happens is acetylcholine can come and bind onto that little pocket right there so I'll pretend it binds onto that little pocket and when it sits on the pockets just like a seesaw it sits on it what's that little gate gonna do it's gonna fly up when that flies up it's gonna open up the ion channel so the ion channel is previously closed but upon the binding of acetylcholine look that the actual gate opens and then guess who can start flowing in sodium ions so sodium ions can start flooding in to this actual postsynaptic neuron and if sodium ions start flooding into this postsynaptic neuron is it gonna start doing to this guy it's going to try to excite this guy it's not gonna cause an action potential it's not gonna D it's not gonna trigger an action potential down the axon not yet the reason why is is you for pretend here we're gonna talk about this more when we get into neuro like on resting membrane potential but here let's say that a cell has a resting membrane potential right here of negative 70 millivolts right then right here we're gonna have a threshold potential and let's assume that that is negative 55 now what is this threshold specifically for let's put here in this bright color actually no let's do it here in purple there's a special channel right here and I'm gonna make it really big here because this channel is very very specific this purple channel here is a voltage-gated sodium channel voltage-gated sodium channel voltage-gated sodium channels only open so this is a voltage-gated sodium channel these only open when you hit a certain threshold negative 55 when acetylcholine binds on to these nicotinic receptors so what is this receptor right here this blue one this is called a nicotinic receptor and particularly of the in category the neuron it opens up these channels and allows for sodium lines to slowly trickle in as the sodium lines slowly trickle in the resting membrane potential starts rising an approaching threshold potential when it approaches threshold potential and hits threshold potential guess what happens these voltage-gated sodium channels open and sodium will flood into the cell and this will propagate down the axon and that is called an action potential so the action potential is generated by the voltage-gated sodium channels but now my question is what is that little blue line representing what did these nicotinic receptors do they generated a little excitation on this postsynaptic membrane and we call this excitation and excitatory post-synaptic potential also referred to as a epsp an excitatory post-synaptic potential that is what's happening here and the autonomic ganglia okay cool what's happening in the central nervous system here's what I want you guys remember acetylcholine is so important they have all these different types of things that they tell you nowadays that you can use or take that can help you to increase your acetylcholine and there's a reason why acetylcholine is so important because in different neurons in the different circuitry of the central nervous system we're gonna have those nicotinic receptors those hey I'm going to put in N and they can be present all over the entire central nervous system and they respond to acetylcholine so whenever acetylcholine is present it combined on to these nicotinic receptors and trigger the different circuitry within the brain but here's what I want you guys remember what is that circuitry responsible for why is this happening what is the significance of it the significance of it within the central nervous system is three basic functions one is acetylcholine plays a significant role in memory of all the importance this is probably of the most important within the central nervous system they've shown studies that decrease in acetylcholine and acetylcholine receptors results in a decrease in memory also they play it plays a role with an arousal and then the last one is analgesia okay okay so that's these three significant things that you should remember with inside of the the neuron circuitry of the central nervous system the basic thing is is cognitive function he plays a significant role within cognitive function of the central nervous system okay and that covers the nicotinic receptors on the autonomic ganglia and central nervous system now I want to talk about the nicotinic receptors that are present on the skeletal muscles if you guys watch our my ology videos we've talked about this in so many different ways so I'm not gonna beat a dead horse here but I'm just gonna say that we have nicotinic receptors and and their structure isn't significantly like important they do have like alpha chains and they have beta chains and Delta chains and gamma chains and stuff like that but um what's important here is that there's different proteins a total of like five different proteins that come together and make this nicotinic receptor now on the nicotinic receptor there's two domains are these little acetylcholine binding sites so these are like these right here are the acetylcholine binding sites it's like our the domain for it right what happens is this is so cool okay so remember within the actual spinal cord we have two different types of neurons we've been focusing primarily on the autonomic okay now if we talk about this next one coming from the anterior horn of the ventral Horn of the spinal cord you have your somatic motor neurons so let's assume that this guy right here is an alpha motor neuron this alpha motor neuron is a somatic motor it only takes one motor neuron to reach the effector organ whereas in the autonomic nervous system it takes two motor neurons to reach the effect organ anyway these action potentials can come down the alpha motor neuron as the action potentials come down the alpha motor neuron you know that there will be calcium like if we kind of zoomed in here the you know there's vesicles here and these vesicles are rich in acetylcholine and what happens is is they're special channels here present on the synaptic nerve terminal which are calcium channels voltage-gated calcium channels and as calcium starts rushing into these axon terminals you remember it activates like synaptic brevis and Taksin and it triggers the exocytosis of acetylcholine now what happens is acetylcholine is going to have to bind on to these sites here so these these - ACH binding sites are domains present on this nicotinic which is present on the skeletal muscles sarcolemma which is just a cell membrane when acetylcholine binds on to this guess what it does normally the channel is closed us constricted all right but then acetylcholine binds on to these two pockets and guess what that sucker opens when that opens it allows for particularly two ions to move in and out of the cell one ion is going to be sodium sodium is going to rush into the cell now as sodium comes into this cell it's gonna make the cell more electro positive in other words it's gonna try to depolarize the cell opposing that there's going to be some potassium and the potassium ions if you look look what I did here sodium is much bigger potassium is smaller than this the reason why is is because less potassium is going to be leaving the cell you know we're gonna talk about sweetheart what resting membrane potentials but if you remember we just have talked about this up there here's our resting membrane potential here's our threshold potential normally in skeletal muscle cells it's approximately around negative 90 millivolts now negative 90 millivolts is close to very close to what's called the Nernst the Nernst potential or the equilibrium potential of potassium normally his is like close to like negative 86 millivolts about so if that's the case then potassium isn't gonna want to leave he's gonna want to stay where the pot with the actual negative ions are because right now the cell is negative and positives are attracted to the negative so because of that not much potassium is going to be leaving the cell instead more sodium ions are gonna be attracted to these negative charges and they're gonna flood into the cell if that's the case then there's more positive ions coming into the cell than there is positive ions leaving the cell that's going to cause the cell to become a little bit electropositive so what should you see here on the graph you should see the graph starting to rise approaching threshold potential this right here that rise going towards threshold potential is a specific type of activity they call this exerted here by the nicotinic receptors they call this a motor end plate potential in other words it's just a graded potential that you're trying to bring the resting membrane potential up to threshold and once you hit threshold we're gonna blast open some voltage-gated sodium channels inside of the sarcolemma and that'll trigger an action potential inside of the muscle cell and then if you remember that will trigger the sarcoplasmic reticulum which release the calcium out there and trigger the whole cross bridge formation to lead to skeletal muscle contraction what's the big point that I want you to get here acetylcholine binds onto the nut nicotinic receptors on the skeletal muscles it actually causes sodium ions to flow in very very little potassium ions to flow out and that creates a motor endplate potential which is just the thing that we need to be able to stimulate these voltage-gated sodium channels and upon stimulation of these voltage-gated sodium channels this will lead to depolarization of the muscle cell and if you depolarize the muscle cell this will eventually lead to calcium release remember we said they love calcium released from the sarcoplasmic reticulum the increase in calcium is going to increase the actual skeletal muscle contraction okay sweet stinking deal okay and that's what you'll see right here all right that covers that part now we've done this part here let's now go on to this part here which is the muscarinic receptors the g-protein coupled receptors another named member we said this is g-protein coupled receptor we can give it another like umbrella term like a general classification and we can call this metabotropic receptors metabotropic receptors is just basically saying these are g-protein coupled receptors okay so cool now what I want to do is I want to focus on the target organs of these muscarinic receptors so in order for us to do that we have to come here to the central nervous system let's say that I focus on a specific cranial nerve doesn't matter which one I'm just gonna say that this is cranial nerve seven let's just say for the sake of it that's this is cranial nerve seven but it doesn't necessarily matter I just want us to get an overall point here cranial nerve seven has this actual nucleus then from that it gives off these axons from this point now these axons that are being formed here and leak going to this actual ganglia this is called a pre ganglionic motor neuron so what do we call this guy right here we call this neuron the pre ganglionic parasympathetic nervous system motor neuron now it gets to this area here to this ganglion we already said that this has what type of receptors here if we blow up this area let's blow this area up a little bit here so now let's blow this area up so we can see this a little bit better let's say here I'm gonna have the axon I'm gonna kind of blow out the nerve terminal here and the same thing here I'm gonna kind of blow out here the cell body okay now what's important for this for us to understand here's the preganglionic motor neuron we already said is going to have these vesicles inside of it and these vesicles which are going to be rich in acetylcholine they're gonna release that acetylcholine right we said that there will be an action potential triggered moving down the axon and if the action potentials moving down the axon it'll open up special channels located within the synaptic nerve terminal which are our voltage-gated calcium channels and if calcium rushes in what do we say happens if calcium rushes in it stimulates the migration of these synaptic vesicles to the actual membrane and by doing that it triggers the exocytosis of acetylcholine now we already know that one of the receptors present here one of the receptors is going to be the nicotinic we already said that that there will be a nicotinic receptor present here it's gonna be the one to trigger the epsp but guess what there's another one present here the other one present here and I'm going to talk about it or just really quickly because then that's gonna lead us into this whole discussion here is going to be a special type of muscarinic receptor and this is where we're gonna start talking about these because muscarinic receptors we set our g-protein coupled receptors these are g-protein coupled receptors so this is a nicotinic receptor this right here is called a muscarinic receptor and we're going to talk about what specific one it is in just a second but in order for us to do that we have to go over the different types of muscarinic receptors and a little bit more detail so let's do that now these g-protein coupled receptors they're a little bit different so that's what I want to talk about first before I go into every specific muscarinic receptor target organ so let's go ahead and focus on M 1 M 2 M 3 and we'll talk briefly about m4 and m5 but not a lot here's what I want you to remember though make your life easier here's what's nice start here with the m1 this is going to cause a positive effect it's gonna try to stimulate its target organ then we go to m2 this is gonna try to inhibit its target organ then just flip back and forth positive negative positive negative positive this is why it's so cool all of the positive muscarinic receptors the ones that have these positive signs they work by a special mechanism that we're going to talk about which is called the GQ protein-coupled receptor the negative ones the muscarinic receptors who have negative signs on them they work through the G inhibitory pathway this is why this is so easy now okay so let's go ahead and look at m1 m3 m5 and then we'll do M 2 and M 4 are their mechanisms so let's put here on the cell membrane let's have our g-protein coupled receptor here so here's going to be this hormone binding domain here or this ACH ACH binding domain and then it has passes through 1 2 3 4 5 6 7 but it'll have an extra one it's fun but it's a serpentine receptor or we call it a g-protein coupled receptor our seven pass receptor and what this guy does is is he stimulates he binds with a special g-protein okay and we said that we're gonna focus here on this one being m1 m3 and m5 okay let's say that acetylcholine binds on to this m1 m3 or m5 receptor if it binds on to this m1 m3 m5 receptor it stimulates a special g-protein located inside of the cell and we said that this is called G Q protein G Q is normally bound to GDP but it gets rid of that GDP instead it binds a gtp this gtp stimulates the GQ protein and activates this GQ protein when it's activated it's going to calm down the cell membrane and activate a protein or an effector enzyme that's located in the cell membrane and this is a special one and this guy is called phospholipase C phospholipase C phospholipase C has the ability to break down a very very integral component of the cell membrane this component here is called phosphate phosphate it'll in a Seidel diphosphate and what phospholipase C does is it breaks that down into two chemicals one is called ina Seidel triphosphate or ip3 the other one is called die Aseel glycerol now here's why this is important if this is some type of cell here it will have some type of endoplasmic reticulum maybe then sarcoplasmic reticulum and what will happen is ip3 will stimulate this endoplasmic reticulum like structure and when it does that it triggers the intracellular release of calcium out into the cytoplasm of whatever this target cell is now upon that release calcium will bind with a protein called calmodulin and when it does that it forms this calcium calmodulin complex which can activate a enzyme call it a calcium calmodulin kinase now the next thing that has to happen is this diacylglycerol it can activate another enzyme and this enzyme is called protein kinase C what happens is protein kinase C and this calcium calmodulin kinase can go and phosphorylate specific proteins and enzymes so what these guys will do collectively is they will come and phosphorylate special proteins and enzymes may be these proteins we've talked about it before may be their channel proteins so maybe these will be channel proteins in these channel proteins they're sensitive to the phosphate groups and if you put a phosphate onto this protein here so let's say that's going to phosphorylate proteins / enzymes you could put a phosphate on this channel that might activate the channel and trigger calcium lines to load into the cell stimulating this cell who knows it might phosphorylate different proteins and enzymes that are from metabolic function so this might be for metabolic enzymes there can be so many different functions of these we're not going to go into all the details but what I want you to understand is the overall goal of this pathway is to phosphorylate proteins and enzymes that can play a very very integral role with an eater changing membrane permeability changing metabolic activities maybe even changing the transcription activity of the actual genes there's so many different things that can happen okay so that covers that part now next thing I want us to see is how does the actual g inhibitory pathway work because this was for M 1 and 3 M 5 that for GQ the G inhibitory is for M 2 and M 4 so let's do this one now let's do this guy and this blue color here so here now we're gonna have our g-protein coupled receptor here's the domain and remember it passes through the membrane a total of seven times what I call serpentine receptors or seven pass receptors and what it does is it's connected with what's called a G inhibitory protein but if you remember G inhibitory these G proteins have three different domains an alpha inhibitory domain a beta inhibitory domain and a gamma inhibitory domain if we release acetylcholine on to M two and M for receptors what will happen is acetylcholine will bind on to this domain here and it'll trigger the activation of this g inhibitory complex this whole complex here is called AG inhibitory protein but what it does is is the remember it gets rid of G DP and binds gtp which causes to become active upon that activation this G inhibitory protein splits into two different components so watch this now we're going to split into two different components one is it splits into what's called the beta inhibitory and gamma inhibitory subunit so look there's that one subunit there the other one is it splits into the alpha inhibitory subunit why is this important generally these beta and gamma inhibitory subunits are very very sensitive they're very very good at binding onto channels that are very sensitive to them you know there's potassium channels and what happens is these beta and gamma inhibitory subunits can bind on to these potassium channels and lead to the potassium ions leaving the cell if that happens what's it gonna do to the inside of the cell make the cell really negative if you make the cell really negative you hyperpolarize the cell if you hyperpolarize the cell it's not going to be very active in certain types of activities and then we'll see where okay the next thing is the alpha inhibitory it does something else you know there was a special different types of enzymes here one special type of effector enzyme is called adenylate cyclase so we call this adenylate cyclase okay and a dentally cyclase can respond to that alpha inhibitory subunit and what happens is it can tell this alpha this adenylate cyclase hey i need you to stop functioning adenylate cyclase normally functions to convert ATP into cyclic a MP and cyclic a MP tries to activate protein kinase a but if you inhibit adenylate cyclase can it convert ATP into cyclic AMP you know can cyclic GMP activate protein kinase a no will you be able to phosphorylate different proteins and enzymes that play a role within membrane permeability or depolarization metabolic enzymes or transcription no this will inhibit the cell so these are primarily for and habituated organs and these are primarily for the stimulation of their target organs that's why this is so cool it's so easy okay now what I want to do is I want to talk about where can you actually find m1 - m3 m4 m5 let's make it easy for you m4 m5 let's put these down here so here is going to be M for and then let's put here let's put muscarinic receptors and we'll split this out again m1 m2 m3 m4 and m5 m4 and m5 are really easy the reason why these are really easy is because these can only be found in your central nervous system so these are primarily found in your central nervous system and when you find these in the central nervous system what do you think that they do come back over here they play a role within memory they play a role with an arousal with cognitive functions and analgesia pain reduction so that is what is important about these muscarinic receptors and they can be found all over all over the different central nervous system so that covers these guys that's easy now okay now we get onto these guys M 1 M 2 M 3 M 1 is really we're going to keep it very very simply R M 1 we're gonna find it in two specific locations that we're only going to talk about there is other places but we're going to talk about the most common ones M 1 muscarinic receptors muscarinic type 1 receptors they are going to be found in generally two locations one of the big ones is again they're gonna be found in the central nervous system central nervous system and again they're gonna play the exact same role that these guys played they're gonna play roles in memory cognition arousal and as well as analgesia now the other location is usually you can find it on what's called your gastric glands okay so usually you can find this in what's called the gastric glands but particularly we're just gonna say the parietal cells okay the parietal cells are actually located within the stomach right so you know the stomach you have we're not going to go into detail on this right now we'll do this more when we get into GI but if you have this like right here you have a specific portion here and they're called gastric pits right and then down here from the gastric pits you have what's called gastric glands and these gastric glands are responsible for producing and secreting hydrochloric acid well what happens is they have receptors very very specific to acetylcholine and actually there's two different types here one they have m1 receptors and when acetylcholine binds on to these it will trigger the release of hydrochloric acid and another thing it will trigger the release of is not just on the parietal cells it can also trigger the chief cells to secrete what's called pepsinogen pep say no gin so these are the two chemicals but it's not just m1 receptors they found down there too they also found another different type of receptor there as well and this is m3 muscarinic receptors so there's two different types here in the gastric glands m1 receptors and m3 receptors but again the basic function here for the parietal cells is triggering the release of hydrochloric acid and even a little bit of this protein digesting enzyme called pepsin again that covers m1 done in two and two is a lot easier it's mainly going to target two different places one is the heart okay so it's going to target the heart so if you know here we have the heart right you're gonna have two different locations on the heart you have the SA node and you have what's called the AV node so let's say say here is the SA node and then here is going to be the AV node and then you have your bundle of hiss and then from the bundle of hiss it splits into the right bundle branch and the left bundle branch right well what's specific here is that there are specific types of receptors present on the SA node and the AV node so let's pretend we put a receptor right here and we put a receptor right here on the SA node and the AV node so one right here this is going to be s a node and this right here is going to be AV node now if the cetyl choline acts on these two receptors so here here's our acetylcholine and it acts on this receptor or it acts on this receptor it's going to decrease the action potentials it's going to hyperpolarize the cell which one of these guys cost potassium I need flux m to an in for potassium ions leave the cells gonna make this cell negative it's going to inhibit this cell that should make sense so what type of receptor should we see here well m4 is only on the central nervous system the only other inhibitory one is m2 so we should expect em to receptors muscarinic type 2 receptors present on the SA node AV node and if you really want they're also present with on the bundles hiss so they call this if it inhibits the SA node negative chrono tropic agent if it inhibits the AV node it's a negative bath mo tropic agent and if it inhibits the actual button little pits it's a negative drama tropic agent ok so that's one we can find it present on the actual heart well that's a beautiful red right so SA node and AV node and yes we can't throw another one on there which is the bundle of hiss or the AV bundle one more area and that is actually going to be present on the pre synaptic membrane okay so you know what ctul choline when acetylcholine is released here you know there's special enzymes that will degrade it called acetylcholinesterase so there is special enzymes here pretend here I'm gonna have him like this here's this like pac-man looking dude here and that pac-man looking dude right there is called acetylcholinesterase so this is called acetyl I'm gonna put a CH that is acetylcholine esterase acetylcholinesterase will degrade the acetylcholine what let's say that acetylcholine is able to come over here there's a special receptor present on the presynaptic membrane that can inhibit the further release of acetylcholine this receptor is called M 2 receptor so you can also have a receptor here this is called M 2 receptor muscarinic type 2 receptor and if acetylcholine binds here it will cause potassium ion efj locks and you'll inhibit the calcium entry by inhibiting the protein kinase enzymes if you do this it'll inhibit calcium release and if you inhibit the calcium entry this is going to inhibit the actual what and then with the release of acetylcholine and it'll trigger what else potassium ions to leave this cell which will make this cell electro negative hyperpolarizing the cell so we can also find M 2 receptors on the presynaptic nerve terminals so pre synaptic nerve terminals and the last one is M 3 M 3 is where you can find pretty much everywhere else so what are some of these areas the big thing I want you to remember is you can find M 3 on any type of exocrine gland any type of exocrine glands so what are some of these exocrine glands that I'm talking about the lacrimal glands the lacrimal glands have M 3 receptor so it's going to increase the production of lacrimal fluid what else salivary glands the parotid the submandibular the sublingual they're gonna have em through receptors increasing the production of saliva sweat glands have M 3 receptors they can start producing sweat and even the pancreas the pancreatic sentai they can make digestive juices what else even the gastric glands to have M 3 worse because that we said okay so I want you remember the exocrine glands could be like lacrimal glands could be like salivary glands could be like sweat glands it could be the pancreatic say nice right or it could even be gastric glands and again that's all going to be a stimulatory effect the next thing is they can act on smooth muscle but the big place is that it can act here let's actually do this one here black no let's do it here and this baby blue color keep it going the next place is it can act on the smooth muscle of the bronchi so because it can act on the bronchi it can produce what's called Bronco constriction okay so it can actually act on the bronchi of the actual lungs and if it acts on that it's gonna activate the m3 receptors m3 receptors load the cells with calcium if you load the cell with calcium it's going to cause contraction of that actual muscle cell and it's going to narrow the airway what else I think about the GI tract the entire GI tract the smooth muscle of the GI tract if you look at the GI tract it should have m3 receptors which is going to be important for what peristalsis and segmentation and hydrochloric acid secretion and pepsinogen secretion and intestinal secretions so it is Pro GI activity so it can be found on the GI tract smooth muscle and again you can remember parasympathetic it's for resting digesting urinating o urinating so what else would it be doing it's going to be helping to allow for urine production so specifically causes the bladder contractions so it can actually cause the bladder contractions what else do we say it does not only does it act on the GI tract to move the food but it helps you to drop the poo right it helps you to drop that log so that's important too because your internal anal sphincter is also having a little bit of parasympathetic tone so because of that it's not only going to be important for it helping to make actual urine but it's also going to be present on the GI tract to allow for defecation so it can help in the process of defecation because defecation is a parasympathetic spinal cord mediated reflex one more place that I want to mention before we end it off here is the eye okay inside of the eye let's come over here for a second inside of the eye you know that there's actually going to be if we look at the eye here here let's say here we have the eye here here's the lens and then here you're gonna have the ciliary body right so here's our actual eye well on this you're gonna have special muscles - special muscles here one is going to be located right here which is a part of the ciliary muscle so there's gonna be the ciliary muscle right here the next one is is there's going to be a part of the iris there's also gonna be a part of the iris these guys have to also have receptors specific to the acetylcholine so on the ciliary muscle it actually has m3 receptors and if you have m3 receptors it's going to load this cell with calcium if the loads the cell with calcium it's going to cause the sealy eros to contract if the ciliary scon tracks it pulls the actual fixed end forward if it does that it costs the suspensory ligaments that hold the lens to become very loose if it becomes loose the lens becomes globular so the lens becomes blob Euler and if the lens becomes globular this is gonna allow for us to only see things that are actually going to be nearby so this is gonna produce what's called near vision the next thing is there's also going to be the muscles here on the pupil so they should have m3 receptors load them with calcium they're gonna contract this is called the constrictor pupil a and if this contracts it'll actually narrow the pupil and if you narrow the pupil it allows for less light to come in and hit the retina our engineers that pretty much covers cholinergic receptors I hope it made sense I hope you guys did enjoy it if you got stuck in throughout the whole video can't say thank you enough I know sometimes the videos can be a little longer but our whole purpose here is to try to make this stuff make sense which is sometimes as a side effect a little longer than we want but I hope that you guys did learn something and I hope that you guys truly did enjoy if you guys did please hit that like button comment down the comment section and please subscribe also if you guys get a chance please hit that Facebook go to check out our Facebook or Instagram maybe even our patreon account alright engineers as always until next time [Music] you

Channel: Ninja Nerd Lectures

Views: 102,949

Rating: 4.9786425 out of 5

Keywords: cholinergic receptors, acetylcholine, parasympathetic nervous system, neurology, muscarinic receptors, nictonic receptors

Id: lvahHd0Bmx4

Length: 48min 38sec (2918 seconds)

Published: Wed Feb 28 2018