Transcript for:
Introduction to the Nervous System

good morning class this is Professor Mariah Evans this is BSC 2085 anatomy and physiology 1 we are going to start the nervous system today I'm going to give you an introduction to the nervous system this lecture which comes in two parts is going to be combined with the three parts of the muscle lecture for this next test so the next test is just muscles and then this intro to the nervous system after this enter to the nervous system will break down the parts of the nervous system and get more detailed about them especially all the parts of the brain and their functions and it's gonna be great okay so the first thing is that when we look at the nervous system we understand that when we started this class we did this overview of the systems and we said that the nervous system was a fast-acting system so the nervous system is the master controller but it's really fast acting it allows us to take electrical responses which is that movement of ions right across the cell's membrane and chemical signals which would be the release of hormones neurotransmitters etc etc and allows us to give a very fast and very specific response to a stimulus very fast so rapid okay now when we look at the input so I could wrap up the entire nervous system and three like phrases sensory input and then we have the integration and then we have the motor output the sensory input is receiving that stimulus the integration is understanding what that stimulus is and deciding what to do about it and then the motor output is the response and the response goes to the effectors the effectors are and always will be skeletal muscle smooth muscle cardiac muscle and glands it's the reason why in the muscle lecture I said that I will base everything that comes after this muscle lecture I can base everything on what we're learning in muscles and that's because the nervous system controls everything and the effectors are muscles skeletal muscle smooth muscle cardiac muscle and the glands so they are the ones that produce that response now in this particular picture right here the person's sensory input is that they you know see the glass of water right they may be thirsty hypothetical is by the way of the brain tells you that you're thirsty and then the integration is the brain right this is the control it says well what do I want to do with this glass of water and then sends that signal to in this case skeletal muscles in the arm and it tells you to pick up the glass of water now I always laugh when I tell people depending on what's going on in your mind right your brain at the time you may pick up this glass of water and you may throw it at the person sitting across from you because you're at a date and he or she said something that was totally inappropriate so you just doused them with water right if you're thirsty the hypothalamus is the part of the brain that tells you that you're thirsty and you pick up this glass of water and you drink it if you are just too angry and general you pick up this glass of water and you might just want to smash it against the wall right so we're gonna talk about how emotions influence our reactions and the brain is the place where we understand interpret and decide what we want to do in response to the stimulus but sometimes if we're in a highly excited state or a very angry state or you know our emotions our emotions get the best of us sometimes we don't think through those decisions very well so that's of course just me getting you warmed up to what's coming okay so I've already said that we're gonna break down the nervous system so the central nervous system is the brain in the spinal cord and that's pretty simple except for in the CNS lectures you're gonna learn all the parts of the brain and you're gonna learn their functions and then you're gonna learn the anatomy of the spinal cord and its functions and so it gets more in-depth but for now the central nervous system is the brain and the spinal cord the peripheral nervous system is that pathway to and from the brain in the spinal cord so I'm going to and from the brain that would be my cranial nerves and if I'm going to and from the spinal cord that would be my spinal nerves when we break down the pns you'll realize we have 12 pairs of cranial nerves so they come off on both sides and then we have 31 pairs of spinal nerves and they come off both sides so both sides of the spine for the spinal nerves but again they're going to the effectors and effectors are always and will always be skeletal muscle smooth muscle cardiac muscle and glands so in this picture here they're just showing you that the spinal nerves excuse me the cranial nerves would be coming off the brain and they're focusing on one specifically this happens to be the facial nerve we'll get there which is cranial nerve number seven but we'll get there when we get into the PMS and then they're showing you CNS happens to be the brain and the spinal cord in general and then here are the spinal nerves right running off of the spinal cord right and then we'll talk about the spinal cord as well in that lecture which is coming up after this series anyway so now with that peripheral nervous system which I've already told is the pathway to and the pathway from right so Braden spinal cord since I started by saying that we have sensory input integration and a motor output you shouldn't be surprised at the peripheral nervous system which is the pathway to that would be sensory or afferent right and the pathway from would be motor or efferent and then you go oh okay so a ferrant is like going towards I tell people like affection so that's the sensory part and then motor or you know efferent or efferent is going to the effectors so the sensory nervous system you see sensory motor services we can break that up and you can feel sensation to your body right so so my means body somatic nervous system so this is your skin and your skeletal muscles and your joints and then viscera are your internal organs so visceral would be internal organs so I can sense right or perceive a stimulus at these locations and then the motor which I already said like the efferent part of it is going to transmit those impulses to the effectors right effectors and then we have two divisions as well the somatic nervous system the effect ders of the somatic nervous system are your skeletal muscle and the effectors of the autonomic nervous system is the stuff that runs automatically and that of course would be ready smooth muscle cardiac muscle and glands so when I tell you that the effectors are skeletal muscle skeletal muscle belongs to the somatic nervous system and then we get smooth muscle cardiac muscle and glands and that belongs to autonomous so like automatic okay now here it is the same thing I just said I promise somatic nervous system is going to be voluntary and it's going to the skeletal muscle autonomous nervous system it's going to be the smooth muscle the cardiac muscle and the glands now the ANS is broken up into two subdivisions they are sympathetic and parasympathetic and these have an antagonistic relationship with each other so opposites the easiest way to remember this and you will have to remember this for the exam the sympathetic nervous system is for extreme conditions extreme environments your body in action so for example if I'm exercising the sympathetic nervous system is working highly right sympathetic division and if I am excited the nervous system the sympathetic nervous system is working you know at peak rates so it's activated so my heart rate increases my respiration increases I get you know increased blood flow to like the surface of the skin and I perspire my pupils dilate all of that sympathetic and that's because some extreme action is happening so exercise embarrassment excitement and even an emergency because flight and fight take place in that sympathetic division subdivision and then the parasympathetic is when you're not doing any of those other activities so the parasympathetic is basically controlling your every day ends and outs maintenance regulation of the body when you're not in you know a state of excitation or you're not exercising or you're not you know in an emergency State does everybody get that so sympathetic nervous system you'll see when we get to the AMS they're gonna call it the e act and then the parasympathetic nervous system is going to be associated with the D activities and we'll talk again more about that specifically when we get to ans now this little breakdown you're gonna see this I think like four times between now and the end of the term because we break it down as far as lecture so the central nervous system will be what's coming next then we have the peripheral nervous system which we break down into the cranial nerves and the spinal nerves then we have the autonomous nervous system and automata system breaks down into sympathetic and parasympathetic and then the very last lecture in this you know anatomy physiology one are the special senses and the special senses are like your sense of smell your sense of taste your sense of sight your sense of hearing right the special senses and it helps you at least it's supposed to help you take all of this information that we learned about this lovely nervous system and understand it okay now in lab you looked at neural tissue or nervous tissue and I told you that the main cells of neural tissue were the neurons but then there's also these accessory cells right these supporting cells and those are the neuroglia cells there are five different neuroglia maybe six different ones that we're going to talk about but there are several different neuroglia cells but the neurons are the main cells so neurons are called nerve cells now the reason why I want to emphasize that they're nerve cells is because I'm gonna go back and remind you that I've already taught you that all of our cells are polarized at rest all of our cells are polarized at rest and neurons are cells right nerve cells not only are they polarized at rest what polarized means is they are negatively charged on the inside positively charged on the outside and the movement of ions across the membrane can change them into a depolarize state which will give us an action in the case of skeletal muscle it would be muscle contraction in the case of a neuron when it goes from being negative on the inside to positive on the inside we get a nerve impulse we get the release of neurotransmitters and then neurotransmitters do one or two things when they bind to other cells they either depolarize them so we can get an action or they hyperpolarize them which is an inhibition I promise that's coming but please just hold on to the idea that neurons are nerve cells and since they're nerve cells a lot of the information that I'm going to talk about regarding the neuron it's going to be the same information that I've already taught you about muscle cells and then don't forget the effectors are muscle skeletal muscle smooth muscle cardiac muscle and glands now these are the four so we're going to do six I think two these are the four neuroglia or the supporting cells right the supporting cells of the central nervous system recalling of course that the central nervous system is the brain in the spinal cord so we have astrocytes the microglia cells epidemic cells and oligodendrocytes ELLs now the astrocytes are the most abundant and you need to know that of course for the exam so the astrocytes are the most abundant of the neuroglia cells and they actually anchor the neurons to the capillaries and when they do that they're basically anchoring the neurons to their food source because glucose white flows through the neurons I mean excuse me through the capillaries and then they anchor them to their oxygen source right because blood which is carrying oxygen is flowing through there but they also help migrate cells where they're supposed to go so the astrocytes play quite an important role microglia cells that prefix micro means that it's small so that makes sense right microscope microscopy right we've looked at cells and tissue underneath the microscope so microglia cells are really small but they have a pretty big job the microglia cells are actually phagocytic cells so they're the type of cells that have the ability to engulf other things and so basically they play this illogical role for the neurons making sure that they're free of debris and then epidemic cells are lining cells so the epidemic cells line you know certain areas and they come in different shapes imagine that and guess what the shapes are ready squamous cuboidal or columnar and then we have the oligodendrocytes and the allyl dendritic cells are myelinated and we're talked about that Miley myelination and what that means but right off the cuff the minute I mentioned myelination I like to say to my students that whenever I refer to a myelinated axon when you hear myelinated I need you to know that that signal the nerve impulse it is traveling rapidly rapidly like up to approximately 300 miles 300 miles in a second it is crazy how fast is traveling so we'll talk about that as well so now everything that I just said I promise is coming up in the future slide so astrocytes look they're the most abundant ones and they help neurons right stay attached to the capillaries and then their functions they support embrace the neurons and they you know guide the young neurons and then that exchange is the oxygen that I was referring to as well as the glucose right the exchange between those capillaries and so that's you know enough right as far as the astrocytes this is a picture of an astrocyte and you can go back and of course read all of the other functions but no the main ones that I mentioned and then we have and I'm sorry about that then we have the microglia cells as I mentioned they're very small right so micro like small and they have the ability to Faygo citize microorganisms and neuronal debris so they keep things nice and clean in that area right that's an image and then here's a picture of a microglia cell in between two neurons then we have those epididymal cells and these like I said they line things so the lining they line central cavities and then they actually have different shapes and the shape ranges from look at that squamous to cuboidal to columnar and then they show you some cuboidal ones that are there then we have those aligote dendritic cells and as I promised that myelin sheath right comes up so whenever again something is myelinated what you are going to associate with myelination is speed so we do have some cells that are highly like in the skeletal muscle which contracts very quickly and could fatigue very easily but then we have our smooth muscle and our cardiac muscle and we know that those contract slower but we want them to so they have slowed ATP ASE's they can track slower they resist fatigue and that's because your heart muscle is contracting every minute of every second of every day that you're alive we're skeletal muscles can contract right and then you can go to sleep and when you go to sleep brother you know they're so not and we will talk about it because we'll talk about you know dreams when you are asleep your skeletal muscles are actually inhibited so we'll talk about that paralysis dream when we get there but anything that's myelinated rapidly right rapidly firing the impulses so then they show you the oligodendrocytes of protein and lipids so it's a lipid protein complex and again it provides insulation and speeds up the impulse now when we get to the peripheral nervous system right the pathways to and from so the nerves right the pathways to and from the brain and the spinal cord we have two more types of neuroglia cells we have the satellite cells which are similar to the astrocytes of the brain in the spinal cord and then we have the Schwann cells which are sometimes called neural EEMA an obscure sorry neural EEMA sites I was like normally my lights so neuro Liman sites and these are actually comparable to the a LIGO dendritic cells so that means then the Schwann cells have myelin sheath just like the Aliaga dendritic cells had the myelin sheath now this is a satellite cell when you look at it you'd be like oh my gosh it looks like a satellite yes looks like a satellite this is that myelinated axon and so these are the myelin sheaths that we see in the Schwann cells and this is a little bit different from what we just saw in the alley go dendritic cells and the fact that we see these little spaces here right between the myelin sheath and those little spaces are called they make me laugh sheathe gaps so gaps in the sheath and they used to be called the nodes of ranvier but they call him like you know sheath caps whatever all right so what do we know about neurons more so the fact that they are nerve cells but what do we know about them they're highly specialized cells they have the ability to conduct impulses they have long did longevity so our neurons live for a very very long time they're a mitotic which means they don't go through cell division and that's important because there was this commercial this campaign a long time ago I'm you know aging myself but a long time ago when they showed an egg frying in a skillet and they're like this is your brain and they crack the egg and put it on the hot skillet and they said and this is your brain on drugs and it's being fried well the reality is that since our neurons don't divide right when we destroy them it becomes obviously problematic and their consequences to that they require they meaning the neurons they require a large amount of oxygen and glucose which is why those astrocytes are so important because they anchor the neurons to the capillaries where they get that glucose and that oxygen the soma of the neuron is the cells body and that should make sense because remember I said somatic nervous system is the body and that's the skeletal muscle right so soma is the body now they also mentioned a pair of carrion but we're gonna call it the soma and it's gonna come up over and over again because we're talking about the somatic nervous system we're gonna talk about you know how we get these synapses between one part of a neuron with another part of a neuron and someone's going to come up again so that's gonna be the most widely used term for the body of the neuron so in that cell body of the neuron right that soma this is where their synthesis takes place this is where they're making their proteins and and you know chemicals are released and the in deposit reticulum this is like the biosynthetic area and that's important so we also see the nucleus and the nucleus has a nucleolus and we've already did our organelles and we know that our neuron a nerve cell so you shouldn't be surprised that protein synthesis takes place there and if there's endoplasmic reticulum and that there's a nucleus does that make sense it's a cell okay now when we look at the soma right when we look at the soma the nucleus is going to be considered like gray matter when we talk about the brain and the myelinated fiber which I told you was that protein and lipid part of it that's gonna be the gray matter I think that's really cool to know right off the cuff because we're going to look at gray matter and white matter in the brain and their function we're gonna look at gray matter and white matter in its function in the spinal cord and now you know that that gray matter is the nuclei or the body part that we see of all of these neurons and there's you know bazillions of neurons within our central nervous system so the neurons have processes two types the dendrites which are usually highly branched and an axon which is usually non branched okay so when we look at a neuron this is the soma right because this is the body this is the nucleus of course these processes here coming off of the soma are called the dendrites in their branched as I said then we have this axon hillock and of course what do you think comes off the axon hillock the axon and the axon is usually not branched so this one is not branched but it's myelinated so this happens to be a myelinated axon now at the very end I'm gonna mention something that should sound really familiar to you axon terminals I didn't see that coming so the reason why I'm mentioning these axon terminals is so that I can go back and relate this information that we're learning anew today to the information that we learned already about muscles skeletal muscle has a neuromuscular Junction and that's because skeletal muscle requires a nerve impulse and if you remember at that neuromuscular Junction it was the axon terminal where the synaptic vesicles the neurotransmitter that bound to the sarcolemma which was the membrane of the muscle cell yes these right here axon terminals which are the secrete Ettore regions what are they secreting the neurotransmitters okay so the dendrites are the reception or the input region of the neuron okay so I'm gonna go back to this picture because they show you an arrow this is the reception the input and then they're going to travel along right and this is going to be the output and the output as you guys recall the motor output right so watch this sensory input follow down really fast because it's myelinated right to a motor output and if this happened to be the neuromuscular Junction then the motor output in this particular taste would be skeletal muscle if this was going to be smooth muscle that takes place there right that would be the effector and if it was you know a gland then that would be the effector and they would be affected by what's being released by the axon terminals which are neurotransmitters and we're gonna learn about neurotransmitters in this lecture today all right so then so the dendrites are the receptive in right and then what that means that the axons of course these are going to be the ones that are going to be delivering so this is going to be the output we follow that area I mean that arrow already and then the axons like I said can be myelinated like that picture that we just saw and the reason why that's important again is because every time you hear that something is myelinated in the nervous system you need to understand it is trucking it is moving really really really fast so they go on to tell you of course that this is the conduction region we're going to be sending it to the effectors this is also going towards the terminal end so the axon terminal this is where the neural transmitters are going to be released and then look here neurotransmitters only have two options now they are because we're in a nervous system they're talking about a neuron coming together with another neuron but I said a neuron could come together with skeletal muscle or smooth muscle or glands right but they're talking about a neuron coming in contact with another neuron and all it says here is that it can cause an excitation or an inhibition those are the only two options and then I'm gonna spoil everything for you right now acetylcholine in skeletal muscle is an excitatory neurotransmitter that means it causes skeletal muscle to be excited and contracting right if it's inhibited if it's inhibited that means it's stopping in action so excited is carrying out some type of action inhibited is preventing it now it gets even better cells are polarized at rest negatively charged on the inside at rest if we want to excite a cell we change it from negative to positive on the inside if we want to inhibit a cell we change it from negative to excessively negative or more negative and that's called hyper polarizations so hyper polarizations cause inhibitions depolarize depolarizations cause excitations and those are the only two options so with 50 different neurotransmitters i only still get two options either i'm gonna get an excitation or i'm gonna get an inhibition now let me break down some more terms polarized is what the resting membrane potential is right negative on the inside so that's one polarize if you're taking notes write it down polarize then depolarized is when I get the excitation that means going from negative to positive on the inside right repolarization means I'm returning to rest I'm returning back to negative on the inside and then our last one which is what I already mentioned here is a hyper polarization and a hyperpolarization is when you have a cell that is at rest negatively charged on the inside and then a neurotransmitter sends a signal and causes ions to either move into that cell or move out to that cell and it makes the cell more negative than it was at rest that is hyperpolarized and that causes inhibitions now it may sound like inhibitions are bad things but not always if I am hyperventilating right let's use some terminology if I am hyperventilating I am breathing too fast and unfortunately I'm breathing so fast that I am not gaining the benefit of oxygen being delivered properly to my tissues hyperventilating I talked about this already but I like to you know bring things full circle so if I'm hyperventilating I'm going to put a paper bag over my mouth and nose and I'm gonna breathe into the paper bag and catch my carbon dioxide and breathe it back in and that's because carbon dioxide is inhibitory and so that's going to inhibit my hyper right think about that my I'm hyperventilating is gonna inhibit my hyperventilation which is breathing in and out it's gonna slow it down to normal because it's inhibited or it's inhibiting a hyper action oh love this stuff all right so let's see but the axons so axons have this you know internal transport that takes place because remember these are cells so organelles move along the axons and proteins etc etc but here's the thing along the axon movement can occur in both directions if it's moving away from the cells body so if it's moving away from the soma we say that that is antegrade right antegrade like it's in the past right Antebellum the past excuse me before like antebrachial forearm my bed and then retro is the pass so if it's moving back towards the body that would be retrograde so when we look at oh I was going to go back to that picture this one so this is the cells body here is the axon here's the axon and if I'm moving away from the this is going to be the antegrade if I'm moving back towards the body then that would be retrograde right like retrospective right looking back okay so now let's look at the functions okay so viruses and bacterial toxins can damage your neural tissue and that's kind of a big deal so you know that we have a vaccine for polio right but most of you guys know about rabies like rabid animals right and we said that they've gone mad right Old Yeller is this you know book turned into a movie that's really sad but anyway the golden retriever gets um you know rabies and he has to be put down because he's losing his mind it's destroying and remember excuse me that the nervous system sorry sorry that the nervous system is a fast-acting control system and so if there's damage that's taking place there it's gonna be really bad so polio can cause a person to become paralyzed rabies can cause a person or a dog like literally to lose their mind and die tetanus which we talked about in the muscle contraction model causes paralysis right so damage to the nervous system has some very you know huge consequences that are associated with that so we are investigating some retrograde transport to treat some of the genetic diseases meaning that you know it's a genetic it was you inherited it so some type of genetic mutation you know cause these things to happen and so they have viruses that have the ability to inject the genetic information into the cells so viruses contain the corrected genes and then they transport those or deposit those into cells it's kind of cool we do this all the time in research by the way have viruses do our work for us because of their method of replication all right so what do we know already about the myelin sheath we know that the myelin sheath is part of a legal dendritic cells and we know that the myelin she as part of the Schwann cells we also know that it is this protein lipid complex that I mentioned already we know that it's white and we also know that this makes up the white matter of the brain and the spinal cord because I mentioned it to you already but let's see what they say about it more than what we've already discussed increases the speed of a nerve impulse so discuss that part already now if we're gonna compare myelinated to non myelinated we already know if myelinated means it's going really fast and non myelinated it means it's gonna conduct more slowly now we also know Schwann cells are myelinated we know that our oligodendrocytes are myelinated but we also know that there's gaps right in those Schwann cells so we look at the Schwann cell itself when it wraps around the axon so this is the Schwann cell this is the nucleus of the Schwann cell so this coiling around the Schwann cell that's what makes it myelinated okay myelinated so the gaps as we said before these are the nodes of ranvier is what we you know used to call them but now they're just called sheath gaps sheath gaps so a gap in the sheath okay anyway and then so know make sure you know nodes of ranvier cuz it's still widely used but those are the spaces that we saw when we looked at the myelinated axons now this is that same picture that we talked about earlier so this is the soma these are the dendrites this is the axon it's myelinated these are Schwann cells and then these are the nodes of ranvier or the sheath gap so myelin sheath gaps now what about those that myelin sheath we know that not only is it in Schwann cells that are part of the peripheral nervous system we know that it's also part of the oligodendrocytes is among the brain and the spinal cord okay so when we look at the comparison right I've already told you because I spoil things that when we look at the comparison of the brain and we talk about gray matter versus white matter that white matter is the myelinated fibers there's some gray in there too but it's mostly myelinated fibers which is why it appears white the gray matter is the body what did we see in the body we saw that nucleus so almost always and we'll talk about this I promise it's going to come up over and over again almost always when we're talking about the gray matter you're gonna see some type of nuclei come after it so basal nuclei is this kind of umbrella term but there's like a caught it nucleus there's a punt iment nucleus the thalamus is gray matter and they're gonna talk about all of those nuclei there's a red nucleus so whenever we're talking about nuclei you think of gray matter whenever we talk about white matter we're talking about the myelinated fibers alright now when we look at neurons themselves multipolar bipolar unipolar multipolar has multiple processes so three or more many dendrites and an axon would make it multipolar but one axon and one dendrite would make it bipolar and then unipolar would just be one process and here it says it's one process and it appears they put in parentheses like two axons but basically what happens is is the body is in the middle and the axon extends from both sides so you know like one but it extends from both sides so a T process is the best way to explain that and then they show you in pictures so this one right here is multipolar multiple dendrites right and one axon so if there's three or more processes it's multipolar this is bipolar we have one dendrite here we have one axon so one dendrite one axon and then this is still an axon so it's one axon but it extends on both sides of the cell body so that's what they mean by that T process and this one is unipolar okay so one and then they show you varieties of neurons that are found in a variety of different places when we get to the special senses a lot of these will come up again so these are the Purkinje fibers these are pyramidal cells these are olfactory which is your sense of smell these are retina which is for your sense of sight these are the dorsal root ganglia so we'll talk about these and how they intervie the gram I communicates that are associated with your back muscles and your intercostal muscles so we'll get there but for now they're just showing you that there's different varieties of multipolar bipolar and unipolar neurons and they're found in a variety of different places you know because their function structure is different therefore their function is different oh my gosh what's this class again and that to me in Physiology okay so now let's look at what happens with our neurons we've already said that the nervous system is sensory input with an integration Center and a motor output so surprise surprise surprise we have sensory neurons motor neurons and inter neurons what sensory neurons would be a part of the sensory input get out of town then integration or inter neurons which are also referred to as Association neurons those are the ones that are making sense of the information and they lie in between the sensory and the motor neurons motor neurons oh my gosh wait motor neurons where could the motor neurons be going to how about the effectors what no way and what are the effectors again and what will they always be skeletal muscle smooth muscle cardiac muscle and glands you will get tired of me saying it and I almost always say at the same order skeletal muscle because I put so much emphasis in the muscle chapter on skeletal muscle and how it works and the release of the neurotransmitter and how it binds to the sarcolemma and causes ion channels to open which causes an end plate potential which then activates an action potential which sends that impulse down into the t tubules which causes the release of calcium the calcium binds to the troponin causes the tropomyosin complex to open revealing the active sites on actin so they can react with myosin heads can't get the head saqqaq though until I get ATP ace to break down ATP then I get head cocking cross bridging power stroking and I need a teepee the powerstroke so luckily for me I just happened to have a teepee and pie so I can put him back together and make a teepee but muscles don't stay in a state of continuous contraction so I need a teepee so I can actively transport that calcium back down into the sarcoplasmic reticulum and that's gonna cause the tropomyosin complex to close covering the active sites of actin I also need what started the whole frickin thing I need an enzyme that's going to break down acetylcholine and that enzyme is acetylcholinesterase and when I break it down I'm going to close the ion channels and that's going to allow my muscles to go back to their resting state why did I bring that up here because when we look at the effectors we can't get away from we can't escape that principle of muscle contraction because the nervous system controls everything and the effectors of the nervous system are skeletal muscle smooth muscle cardiac muscle and glands so once you know and understand how skeletal muscle works then you'll understand how smooth muscle works and smooth muscle is the rest of the viscera then we have cardiac muscle and we have glands and those are the only effectors those are the only motor output right resources are effectors so you can't escape it now when we look at and again we'll get to these when we get to the special senses this is me again telling you about those specialized types of multipolar bipolar and unipolar neurons and so they just show you here like inter neurons right those are the Association neurons and that motor neuron go into the effector and then they show you specifically this is skeletal muscle and then even in the eye so when I tell you that you can't escape it by the way if you don't know this we have muscles in our eye what shut the front door and the muscles in your eye our skeletal muscle nah yah-ha because if I asked you to look up right now whether you decided to or not if I asked you to look up right now it was voluntarily to do so or not and if I asked you to turn your eyes in circles you could do that if you rolled your eyes at me and you're like oh my god here she goes again I can't see you so it's okay to do that and then if you you know cross your eyes all of that is voluntary right voluntary so skeletal muscle smooth muscle cardiac muscle glands all of this is important I promise effectors of the nervous system now this is cool stuff to me because so much of this information right here is going to be as I promise related back to skeletal muscle the reason why I do that will become evident and clear in a you know another lecture but for now what I want to tell you is that this next test is just muscle and this intro to the nervous system right muscles in this introduction to the nervous system so the more of the nervous system that I can relate back to muscle the more likely you are to understand it and be able to recall it when you get ready to take this exam so like all cells a neuron nerve cell has a resting membrane potential nah yah-ha and that resting membrane potential means that it's negatively charged on the inside additionally there's more to it potassium is the major intra cellular cation of nerve cells because it's still a cell and sodium is the major extra cellular cation you know why cuz a neuron is a nerve cell neurons are also highly excitable you know just like muscle cells were excitable so cool now other things that we learn because about this chemistry opposites are attracted to each other shut the front door you mean professor Evans is going to take the chemistry lecture from Chapter two and related to the nervous system lecture which is chapter 11 yes that's exactly what Professor is going to do so opposite charges are attracted to each other and the inside of a cell when it's at rest resting membrane potential it's negative and the outside of the cell is positive and all they're saying to you right now is that even though they're on opposite sides of the membrane they are what to each other attracted to each other Bennett says that energy is liberated when the charges move towards one another Oh liberated so that means there's potential there I know uh uh uh presenta as I cool when the opposite charges are separated the system has potential energy potential resting membrane potential uh uh so now let's talk about some of these terms just so you understand you already know about voltage-gated ion channels I'm just gonna bring it up again because when you connect new information to old information you're more likely to recall it for the exam but voltage-gated ion channels were the type of ion channels that didn't open until they received a change in charge just so happened to be that an end play potential was a localized change in charge and an action potential was a moving change in charge right so then what is voltage voltage is that measure of that energy that's there that's generated by those separated charges I know and we measure it in volts or millivolts okay now we have current which is the flow of electrical charge for us though what's causing the electrical charge I know I know don't tell me don't tell me those positively charged ions which are called cations and those negatively charged ions which are called anions and then of course remembering opposites attract so the flow of ions right across the membrane generates a current I know is this great well let's think about that current if something is resistant to the flow it hinders it right it kind of prevents it from flowing the way that it should so if it's going to be resistant we're going to call that sorry low resistance is going to be a conductor high resistance would be an insulator so we live in Florida you guys know that Florida's the lightning strike capital of the world and you should know that you should not go outside in a lightning storm with an aluminum handled umbrella you know why because aluminum is a metal and metals are great conductors why because they have low resistance to that electric flow I know I know rubber tires insulators right insulators high resistance against that electrical flow in this case ions okay now give me a minute why I meditate oh oh and then one more time for good measure Oh law tells us that there's a relationship between current and voltage listen to this if the current if the current is going to be the measure of voltage divided by resistance what that means is the more resistance there is the less current there will be so that is inversely proportional right but if I have more voltage I'll have more current so what's the relationship between voltage and current that one is proportional increased voltage I will increase the current that's proportional if I decrease voltage I will decrease current that's proportional but resistance is inversely proportional increased resistance is going to cause my current to go down and a decrease in resistance will cause my current to go up that's inversely proportional okay Oh law okay now let's look at these ion channels why does this even matter well because only two things can happen to a cell it can be excited or it can be inhibited and that's because the other two things were rest and returned to rest right so resting membrane potential is what all cells are doing when they're not carrying out in action if they become depolarized then they're excited and they're carrying out in action either muscle contraction or nerve impulse in action then they could be inhibited by hyper-polarization and then a return to rest is just going back to the way things were so there's only two options right either I can depolarize a cell or I can hyperpolarize a cell cuz repolarize means I'm just going back to rest so let's talk about how these ion channels play a role in that well there are some leaky ion channels leaky are unguided if it's unguided like if you live in the subdivision that's unguided that means anybody right can go in and out all willy-nilly right there's nobody stopping them from going in and out of the neighborhood right but if you live in a gated neighborhood you have to have access access has to be granted to you so you either have your little barcode that you can open up the gate or you might have a remote that you can open up the gate or you could have you know your security people who open up the gate for you whatever the case may be but it's gated which means that it stays closed until something tells it to open and in this case we have three options it can be chemically gated when like ready a neurotransmitter perhaps binds to the receptor on a chemically gated ion channel or it could be voltage-gated that means that the voltage-gated ion channel received a change in charge that opened up the gates or mechanically gated and mechanically gated ones are an actual physical an actual push or a pull something that is directly applied to opening of the gate now I liken this to the fact that sometimes the gate in cheval stops working and so it doesn't matter if you put your code in does it matter if you have your you know your barcode on your window it doesn't open so what they do somebody mechanically opens the gate and then they leave it open until somebody comes and fixes it but mechanically gate is physically right opening voltage-gated will only open when there's been a change in charge chemically gated will only open when a chemical has bound okay and we've already talked about chemically gated in the skeletal muscle lecture cuz acetylcholine bind to the sarcolemma opened up chemically gated ion channels then we know that the action potential propagated down into the t tubules that opened up voltage-gated ion channels and released calcium we also know that the adjacent voltage-gated ion channels to the N play potential those opened when the endplate potential was initiated so we are familiar with because of the muscle contraction model and information we're familiar with those two already mechanically gated we'll get to those when we start talking about the special senses but just understand that a gated ion channel means that it will not open until something specific happens and that's what it says either binding of a chemical or a change in the membrane potential or some type of physical right physical deformation like a push a pull etcetera so chemically gated voltage-gated and mechanically gated ion channels then they show pictures so that you again get this idea so this one right here is chemically gated ion channel this of course is a membrane rights to the phosphate heads lipid tails phosphate heads and so this receptor is a protein receptor and this is whatever the chemical is right so the chemical has to bind to open up the door so this is the place where the chemical would bind if the chemicals not bound then their clothes and in this case they're telling you that potassium can't go out and sodium can't come in when this chemically gated ion channels closed but when the receptor receives the chemical look what happens opens up this ion channel and in this case like muscle contraction sodium comes in and potassium goes out like in muscle contraction then nearby voltage-gated ion channels and I love this picture because they put these two next to each other because in muscle this was what started my end potential remember that localized change in charge and that localized change in charge is what activated nearby voltage-gated ion channels which allowed more sodium to come in so all they're showing you right here is that this is a voltage-gated ion channel see how its negative on the inside and positive on the outside when it's negative on the inside it's closed but when it changes from negative to positive on the inside voltage-gated ion channels open and in this case just like muscle contraction an influx of more sodium and that of course initiated the action potential that propagated out into the t tubules now listen to what it says and it makes perfect sense if you were trapped someplace and you were on the inside as soon as the door opened you'd be rushing out because you were trapped inside if you were trapped outside and the door opened up then you would like run in so all they're saying is that when those gated ion channels open there is a quick diffusion so ions that were on the outside rush in and ions that were on the inside rush out I know that's so cool so we do have this electrochemical gradient that occurs because we do have this electrical event and this chemical event that's taking place together right electric or the ions flowing across each other chemical would be the chemical that had bound to its receptor and then we look at Ohm's law again and we realize that that voltage has to do with my current in the resistance less resistance right less resistance than I'm going to have more flow right less resistance means I'm gonna have more flow but if I have high resistance then I'm going to have a low flow and by that I mean this flow of these ions across the membrane I know so great now resting membrane potential of all cells but since we're talking about the nervous system they're being very specific and they're saying the neuron they're saying it's minus 70 in the muscle lecture I told you that they said it was minus 90 and I told you didn't have to remember that number you just had to remember that it was negative and that's true but all they're saying here is a neuron at rest has a resting membrane potential so the inside is negative they've measured it they've measured it and it's at minus 70 so being negative on the inside has a term the membrane of a neuron is said to be polarized just like the membrane of a muscle cell is said to be polarized in that cool now when we look at this potential which is that separation of those negatively charged and positively charged inside and outside of the membrane we're saying that the intracellular fluids ionic composition is what determines its negativity and the extracellular fluid so this is ICF intracellular fluid this is ECF extracellular fluid we're saying that the differences in the ions inside and outside of the cell is what causes the potential in that cool then there's differences in the membranes permeability and we know that permeable means that some things can get across and some things can right so look at this they have measured the inside of a nerve cell this is the axon it's negatively charged on the inside and that's the number it's negative these seven 70 millivolts now look what it says here this is not new stuff I promise you it says that the extracellular fluid has a high concentration of sodium let me get this straight sodium is the major extracellular cation it's the same thing but as saying intracellular fluid has a higher concentration right extracellular fluid has a higher concentration so sodium intracellular fluid has a higher concentration of potassium so potassium is the major intracellular cation the way that I help people remember this is if I were you know in the classroom on the board I draw a circle like it's a cell and I put a big K inside of it and I call it Circle K and you're like oh my gosh yeah circ okay it's like a gas station yeah anyway so Circle K what does that mean it means that potassium is in highest concentration inside of the cell when the cell is at rest when the cell is at rest which means then if I want the cell to carry out an activity I need to open up ion channels sodium goes in potassium goes out and now the cell is D polarized giving me some type of event excitation potassium plays the most important role in the membranes potential circle-k potassium is the qualifier there circle-k all right so now all it tells you here is that we already know that there is permeability in the membrane and it's telling you that there's differences like some things can easily get in so the membrane itself is basically impermeable to large negatively charged proteins so an ionic right negatively charged it's slightly permeable to sodium which is why sodium is attached to you guys ready voltage-gated ion channels voltage-gated ion channels because the sodium potassium channel is one channel and that one is usually opened by chemicals binding and then the sodium channel was voted gated which means once we already started this change in charge and a localized formation that's when we got the opening of the adjacent sodium gated ion sodium channels which are voltage-gated ion channels and then it says here that when we look at again permeability the membrane itself is 25 times more permeable to potassium than it is to sodium that's why they keep saying that sodium is the major ion that helps maintain the membranes potential in that cool and then the membrane itself quite impermeable or questionably quite permeable to chlorine now the sodium potassium pump we already know about it we talked about it in the chemistry lecture we talked about it being an active transport we talked about it being a primary active transport we talked about it in the muscle lecture we said that once we restore the membranes potential so I carried out an action and now I need my muscle cells to rest now I have to restore the ionic balances and luckily for us we just so happened to have this pump that's called the sodium potassium pump and what it does is pump potassium back inside of the cell and pump sodium outside of the cell so that we can restore the ionic balances and that neat sodium potassium pump now it says here that when the sodium potassium pump is working it pumps out three positively charged sodium see pumps out three positively charged sodium and pumps in two positively charged sodium or potassium and the reason why it does that is because if there's three positive things going out and only two positive things going in I bet my cells gonna be negative on the inside you know what I can liken that to your bank account if you go and deposit two hundred dollars into your bank account and withdraw three hundred dollars out it's going to be negative even if you go back and deposit another two hundred dollars into your bank account and withdraw three hundred out it's gonna be negative and if you go get my point so I know asuka so three positive things going out two positive things going in now what do we know about the membrane we know that it's potential can change when ions move across it no oh yes guess what in the nervous system we have two types of signals we have a graded potential and we have an action potential lo and behold action potential is an action potential is an action potential action potentials can travel long distances and never lose their strength but graded potentials are localized graded potentials kind of stay in the area where they were initiated and if they try to move away from that area where they were initiated they dissipate that means they lose their strength okay now oh look terms I've never heard of before ever depolarized hmm becoming less negative you know going towards positive hyperpolarized more negative than it was at a resting state inhibition so depolarizations calls activations hyper polarizations calls in Hebei she's let see what they say they say that when I'm going towards positive right so when I'm going toward zero or above because I was negative on the inside the probability of producing a nerve impulse increases X citation hyperpolarization I'm going more negative I was already negative at my resting state but now I'm more negative that decreases my probability of sending a nerve impulse so that inhibits the nerve impulse I know I know only two things that can happen excitation or inhibition it's gonna be so cool now all they're showing you here again is a depolarization in a hyperpolarization an increase of a nervous and nerve impulse being sent that would be depolarize state that's my action going from negative to positive and then hyperpolarization going from negative to more negative or excessively negative that's my inhibition okay you all right part two nervous system now this we ended part one by talking about how a greater potential is going to be localized and an action potential is going to be able to travel long distances so look what it says here graded potentials are short-lived localized changes in the membranes potential so changes in charge right changes in charge now when we look at a graded potential this is what I've already said is that it's going to dissipate from the area where it was initiated so graded potentials in the nervous system are comparable to an end plate potential which we saw in skeletal muscle right localized they show you this is where the potential the change took place and when it dissipated or moved from the initiation site then it lost its strength see that travel short distances decays very quickly dissipates is the word that I use now action potentials are action potentials are action potentials and they travel a long distance right so it says here that with an action potential we get this reversal of the cell's membrane going towards positive by the way this means approximately this is not a negative sign this means approximately so a change in voltage from being in the case of neurons minus 70 to becoming positive 100 is a change in charge right from negative to positive and so in nerve cells and action potentials called a nerve impulse right in nerve cells an action potential is called a nerve impulse it says here that that action potential or nerve impulse involves opening up specific voltage-gated ion channels now this was my promise my promise is is that you fully understood if you took the time to fully understood what was happening in the muscle lecture then when we got to everything else I could apply it but you have to understand and learn and apply what was in muscles before my applicant to everything else that comes next would make sense so in muscle and play potential localize change in charge in the nervous system we have a graded potential localize change in charge and action potential is a moving change in charge never loses its strength right causes the muscle to contract in neurons and action potential sends a nerve impulse excuse me now look what it says about generating this action potential and this shouldn't surprise you at all and involve sodium and potassium ion channels what yeah and at a resting state the sodium potassium ion channels are closed then it says there's also sodium channels that are voltage sensitive wait what sodium channels are voltage-gated ion channels yes yes they are so look what else happens depolarization happens when I open up those sodium channels excuse me and sodium influxes or comes in isn't that neat we know this already then it says we have a threshold give me one second so now sodium channels right sodium channels potassium channels if I'm going to repolarize right if I'm gonna repolarize I've got a stop sodium from going you know into the cell and all it says here is that when we repolarize this means the cell is returning back to its resting state so terms that we already know polarized is what the neuron is at rest because we're in a nervous system that means that it's negatively charged on the inside and positively charged on the outside when it becomes depolarized it's going towards zero because it was negative right towards zero and eventually to positive so from negative to positive is my depolarization repolarization is going back to right returning to the resting membrane potential and then as you know and it's not here because it's not applied to the action potential or graded potential but we know that if membranes are going from negative which is what they are at rest to more negative or excessively negative that it's going to be hyperpolarized now here's the deal how can I get a cell to become hyper polarized well if it's already negative at rest right if it's already negative at rest and I lose potassium which is positively charged the cell will become excessively negative if I let a cell that's at rest which is negatively charged on the inside if I open up the chlorine channels and chlorine goes in which is negatively charged the cell will become more negative right so all it says here is that for hyper polarizations if I get an excessive release the flux of potassium the cell will become more negative which makes it hyper polarize which means it will be inhibited so remember those terms polarize depolarize repolarized hyper rise they will come up again obviously here in the nervous system then we also talked about them in the muscle lecture but don't forget what comes next what comes next every single system like in 2086 every single system that we didn't complete in 2085 is going to be based on this exact same principle the movement of ions across the cell's membrane understanding and remembering that the resting membrane potential means that cells are negatively charged on the inside and I can apply it to every single physiological process I know it's so cool all right then they just show you pictures of the events that take place with the depolarization right and then a repolarization and even hyper polarizations that can occur there's a nice sort of videos you can click on them there so kind of cool now things we already know because of the muscle contraction the repolarization sets the electrical conditions but not the ionic conditions meaning when those sodium channels were open a bunch of sodium came rushing in when the sodium potassium channels were open a bunch of potassium went rushing out so now I've got to restore it back to circle-k meaning I got to get sodium back in to excuse me get potassium back into the cell and highest concentration because a lot of it left and I've got to get the sodium to get out and that's what the sodium potassium pump does remember so it's gonna pump out three sodium and pump back in to potassium so that we can get back to the ionic conditions of circle-k more potassium inside than outside more sodium outside than inside and understand this holds true to nerve cells which are neurons this holds true to muscle cells whether it's skeletal muscle smooth muscle cardiac muscle or glands this excuse me not glands but this holds true to all cells that are in the body so your cardiac cells your liver cells all cells nerve cells muscle cells blah blah blah blah blah okay and then this is the whole idea about pumping out 3 so these are the three sodium that are being pumped out and then to potassium that are coming in sodium potassium pump now threshold was also something that we talked about in the muscle lecture remember something was sub threshold nothing happened sub threshold nothing happened when we got a stimulus that was threshold then I saw right on the my Oh gram I saw my twitch right so I saw the contraction so and we have an all anon phenomenon so if I get to threshold I'm going to get or trigger an action potential and once I get an action potential there's no stopping it so it's the same thing that we learned in muscle cell so all it says here is that the membrane is polarized and then when it becomes D polarized this is about 15 to 20 you don't need to know this number but you need to realize this is positive then we know that it started off as being negative so the membrane is polar depolarize when it reaches threshold that causes this influx of sodium a lot more sodium comes in then potassium that goes out and then we get our action potential and the action potential happens it either does or it doesn't all or none so I make it to threshold and send an action potential or if I'm below threshold I'm not going to get an action potential so all this says here is that all d polar depolarization events don't necessarily produce an action potential okay now we already know these terms right propagation it's moving right propagation allows the action potential to move right we know this because muscle contraction when we got those sodium channels to open because of the endplate potential we initiated that action potential that propagated down the membrane and into the t tubules right so this propagation is this movement so it leads to a depolarization of that area which then causes a depolarization of the area next to it which then causes a depolarization of the area next to it so ready it's a moving change in charge I know it's so cool then it says once it's initiated its self-propagating I mean it's alma go if it's a non myelin axons it happens a little bit differently than myelinated axons but we know that too we know that if it's in myelinated axons meaning this nerve impulse occurring in myelinated axons we know that it's gonna happen really fast and we know that if it's a non myelinated axons that it's gonna happen a little bit slower how cool is that now all action potentials are alike in the fact that once we initiate it right it's all or none once we initiate it independent to what the stimulus is they are alike so an action potential is an action potential is an action potential regardless to whether it happens in skeletal muscle smooth muscle cardiac muscle or in the nervous system an action potential is an action potential is an action potential but we do have some weak stimulus that may not generate an action potential so higher frequencies of a stimulus may generate an action potential so let's just go back and say this again not all graded potentials not all changes in charge not all stimulus will give us an action potential okay now things that are going to encourage the speed of that action potential the speed right the velocity diameter myelination and then look at this third one which is funny to me by golly there's three things sorry oops I'm going to wrong way so dilation or diameter excuse me if it's dilated it means it gets bigger so the diameter a bigger diameter is going to give me less resistance and more flow and then the degrees of myelination if it's highly myelinated it's gonna go really fast if it's lightly myelinated or there's no myelination then it's going to go slow so these things that we've already learned right about myelination is gonna speed it up and then the diameter the way that I like in axon diameter is I give you a comparison between a regular garden hose at your house and the water hose that comes off of a firetruck now the water hose that comes off a firetruck is huge right that diameter so yours this large right flow of water high velocity flow of water that's coming out of it and in your garden hose there's a low right low velocity so that's the diameter now when we look at the type of problems that occur knowing and understanding that myelination increases the speed we think about multiple sclerosis which is an autoimmune disease if you know anyone who's ever been diagnose what multiple sclerosis you know that they have explained or said sometimes they feel paralyzed like they just can't move so let's think about this in somatic nervous system skeletal muscle right those neurons are ready highly myelinated the impulses travel very fast if I have damage to the myelin sheath right if I have damage to the myelin sheath it slows down the impulses it slows down my motor output in that interesting so multiple sclerosis autoimmune disease attacks the myelin sheath right attacks the myelin sheath and as a result of that visual disturbances weakness and loss of motor control speech disturbance disturbances incontinence so your bladder is smooth muscle hmm muscle muscle and muscular control could be a coarse skeletal muscle or your smooth muscle visual disturbances remember I talked about the muscles that are in your eye but more importantly when we get to the special senses you'll see that we have to send impulses or receive impulses in order for us to see properly and those impulses start or generate with light but we'll get there so how do we treat this well since the attack is on the myelin sheath and it's your own body that's attacking it the only thing we can do is kind of suppress the nervous I mean the immune system so that it doesn't attack the myelin sheath we may not be able to prevent it but having high levels of vitamin D reduce the risk of developing isn't that interesting multiple sclerosis now again about the speed right of the impulse we have Group a group B in Group C fibers and this is the one that I was talking about traveling 300 miles per second these are the highly myelinated ones somatic uh-huh somatic it's a skeletal muscle these are the highly myelinated ones and these travel again about 300 miles per hour this is what that hundred and fifty meters per second is and then I think I said 300 miles the second but I'm sorry anyway and then Group B our intermediate diameter so not as large as a diameter and then only lightly myelinated instead of highly myelinated so they move a little bit slower about 330 miles per hour or 15 meters per second then we have Group C small diameter unmyelinated so these travel the slowest about one meter per second I just want you to know that's still fast it's a nervous system and that's about two miles per hour so when we classify them you won't have to know the specifics Group a group B group C but you do have to know that if there is a large diameter and a high degree of myelination that they're traveling the fastest and if there is no myelination and a small diameter then they're traveling the slowest okay now what happens when we get these these things that interfere with action potentials being sent now sometimes it can be a good thing so like when you're having surgery and they block your perception of pain that's a good thing anyway impaired action potentials can be caused by chemical or physical factors so anesthesiologist right or local anesthetics can block voltage-gated sodium channels and if I don't open up those voltage-gated sodium channels I don't initiate an action potential cold temperatures or continuous pressure can interrupt the blood flow and remember neurons need lots of nutrients lots of glucose and lots of oxygen so if I interfere with the delivery of oxygen and to prevent the impulses from traveling so your fingers I live in Michigan and I was born and raised there and it gets really really really cold even with gloves on your fingertips can get really really cold they become numb and that's because they're so cold that they interrupted the blood supply if you sleep on your leg wrong sleep on your arm wrong right then you know that your foot can go numb or your arm can go numb and that's because you had put so much pressure that you again interfered with blood flow and that's where you get those little you know numbness and those needles right we call them needles that tingling that you feel now synapses is when two neurons come together and this parts really easy in the you guys have already taken the exam right yeah so did it end today I'm sorry cuz I don't want to talk about that okay so synapses I think it's ended so synapses are where two things come together and in the joints it was named the joints were named for the two bones that come together in the nervous system the synapses or the junction is named by the two parts of the neuron that come together and this parts really easy we're gonna talk presynaptic and postsynaptic a little bit more because we're gonna talk about it in the peripheral nervous system but precip Natick just means before right and then post hypnotic means after the synapse like where they come together so when we talk about the synapses in general we have if it's an axon of one neuron that's coming together with the soma because this is what they're saying here the soma of another neuron this is called axial somatic axial like axon and somatic like soma so axial somatic EXO somatic EXO dendritic would be an axon and a dendrite and then axial acts on it axons and axons dendro dendritic tendrá new dendrites and dendrites soma dendritic or dendrites and so Mo's right so these are the synapses these are where they come together now in addition to naming the synapses or the the junctions by the parts of the neurons that come together we can have a chemical synapse or an electrical synapse but I feel like you know this already the chemical one would be because like neurotransmitters right those are chemical the electrical ones would be because of the flow of ions right so chemical synapse and electrical synapse then of course in this picture they're just showing you a variety of synapses now let's talk about those chemical synapses let's talk about those neurotransmitters and then I'm going to spoil it right here right now again we have about 50 different neurotransmitters but of the 50 different neurotransmitters there's only two things that they can do they either cause an excitation or they cause an inhibition if they cause an excitation they cause the cell to go from negative to positive right so from polarized to depolarize if they're causing an inhibition they cause the cell to go from negative to excessively negative or more negative now neat things here because I like to go back and reference things to that muscle chapter which I said that I would do and I would do it often it says an electrical impulse can change to a chemical impulse and then back to an electrical one you guys ready I'm gonna go with muscle contraction so calcium which is positively charged ions diffused into the axon terminal calcium positively charged cations right diffused into the axon terminal that is electrical because that's a movement of ions right that caused the release of acetylcholine what is acetylcholine it's a neurotransmitter so that means it's chemical then the acetylcholine bound to the sarcolemma which was the membrane of a muscle cell and when it bound to the membrane of a muscle cell it opened up chemically gated ion channels that let sodium come into the cell and potassium to leave the cell so I'm now back in electrical we met electrical to chemical back to electrical I know muscle contraction it's like Oh so what do we know about the chemicals that are being released there are no transmitters they are in these little synaptic vesicles and they have to move across the synaptic class clef I'm bringing that up because in this case they're going to talk about a neuron coming together with a neuron and muscle we knew that the rate limiting step right the rate limiting step is the release of the neurotransmitter before we got the muscle contraction so what happens is is even with the release we've got to get that neuron or that excuse me that neurotransmitter to pass the synaptic cleft before it gets to its target so when we look at that movement right across the synaptic cleft axon action potential arrives at the axon terminal voltage gated calcium channels opened and that entered into the Alexan axon terminal this caused the release of the neurotransmitter and these are things that we know the road transmitter moved across the synaptic cleft then bound to its receptor chemically gated ion channels I know then it says the binding of that neurotransmitter opened up ion channels which created graded potentials localized changes in charge and then we get to options because of the flow of ions we get two options excitatory meaning the flow of those ions could cause the cell to go from negative to positive or we get inhibitory which means the flow of the ions could cause the cell to go from negative to excessively negative how cool is that we're back to where we started basically now how can I turn eight the effect of the neurotransmitter well and skeletal muscle since acetylcholine is what causes the excitation of skeletal muscle we released an enzyme that degraded it so degradation by enzymes acetylcholinesterase breaks down acetylcholine another thing that happens is just re-upped ache so we released the neurotransmitter it did its job we just take it back up re uptake or the release of the transmitter instead of destroying it or taking it back up it just moves away from the synaptic cleft so it's no longer bound to its receptor so it just diffuses away so those are the three ways to terminate the effect of the neurotransmitter neurotransmitters only have two effects either excitation or inhibition x' excitations are going to cause depolarizations in additions are caused by hyper polarizations and I can terminate the effect by degrading the enzyme there'd excuse me degrading the neurotransmitter with an enzyme like acetylcholinesterase does to acetylcholine I can do reuptake and I'm going to stop for just a second to explain to you a real take example just to help you again understand so we have treatment for depression and we use SSRIs now what SSRI stand for our selective serotonin reuptake inhibitors it sounds like a whole bunch but let's break it down rehab take would do what terminate the effect of a neurotransmitter right we're talking specifically now about serotonin so what we've done is is we've inhibited the reuptake of serotonin which means the effects of serotonin will not be terminated and serotonin makes you feel better people who have depression usually have deficiencies in serotonin so selective serotonin reuptake inhibitors inhibits the reuptake of serotonin that means that we prevent the termination of serotonins effect and that cool SSRIs okay okay this is just showing you again the synapses and so this happens to be of course the axon terminal this is the soma of the other neuron and they're showing you how calcium diffused into the axon terminal how the neurotransmitter is going to be released from the synaptic vesicles how it's going to move across the synaptic cleft then it's going to get to the receptor and then I thought they had a larger magnified picture that's my fault I didn't do one and then they show you that when it opens up the ion channels because they're chemically gated ion channels the way that we can terminate the signal is that we can re-up take which means just take it back up or we can degrade it I'm sorry this is so small we can degrade it with an enzyme or it just diffuses away from the synapse okay now synaptic delay right so I release the neurotransmitter it's got to get across that synapse right and the the cleft it's like you know this area so believe it or not it's the rate limiting step in nerve impulses as well but here's the kicker the nervous system works really really fast so it says the synaptic delay takes point three listen to that point three that's a fraction 0.325 milli seconds so even with a delay the nervous system works really really really really fast right and because it's so fast it's not even noticeable but they just want you to know right that there is the release of the neurotransmitter and it's got to get across the synaptic cleft and then bind to its receptors so the chemical synapses are very common in the nervous system neurotransmitters fifty different ones electrical synapses are not as common they do happen of course memory change electrical to chemical to electrical right but electrical synapses are not as common as the chemical synapses but they do occur very often we see them in embryonic tissue when they do happen it's a connection that takes place oh gap junctions uh-huh gap junctions like we find in cardiac muscle anyway communication happens very fast indirection could be in in one direction or it could be in both directions with these electrical synapses now see down at the bottom where it says that we can have basically again two things excitatory postsynaptic potential or an inhibitory postsynaptic potential see post synapse means after the synapses right occurred so what does the neurotransmitter do one or two things causes an excitation or causes an inhibition would any of you be surprised to see that on the next pages they're good as or the next slides that they're gonna say in an excitatory event that the cell is going to become depolarized you shouldn't be and for an inhibitory event they're going to tell you that the cell becomes hyperpolarized you shouldn't be because that's exactly what it's going to tell you so right here when I have an excitatory postsynaptic potential I get an influx of sodium so more sodium comes in than potassium leaves and I get a depolarization there's my excitatory postsynaptic event then for inhibit inhibitory one look what it says the flow of ions is gonna cause the cell to become hyperpolarized how how does it become hyperpolarized if i lose a bunch of potassium so I have a 'if Lux of potassium from a cell that's already negative it's gonna become more negative if I have an influx of chlorine which is negative it comes into a cell that is negative it's going to become more negative so surprise surprise inhibitory postsynaptic potentials are associated with hyper polarizations excitatory postsynaptic potentials are associated with depolarizations I can apply the information that I've learned about polarized cells every cell in the entire body at rest to depolarize cells getting an excitation or an event to hyper polarization which is an inhibition and then repolarization is going back to rest I can apply that to you guys ready every single system in the body so when I start talking about physiology in the body's function it is about the flow of the ions across the cell's membrane and how do I get those flows well if I have a chemical event and it's a release of a neurotransmitter I know isn't that great or or I can get an electrical event an electrical event could be the cause or the scuse me the effect of the neurotransmitter binding so the nervous system controls everything and we know this already so math is important right so excitatory postsynaptic potentials can be added to other excitatory postsynaptic potentials so summation means I'm adding them up together and the more of those that I'm able to get the more likely I am to get an excitatory event right because I have a bunch of excitatory postsynaptic potentials but I can also unfortunately I can add in inhibitory ones so if my inhibitory postsynaptic potentials outnumber my excitatory postsynaptic potentials then my overall outcome is inhibitory so I can add excitation to excitation to excitation to excitation and I can add excitations to inhibitions and the excitations could cancel out the inhibitions and abyssion could cancel out the excitations so this is this war between them but in all reality the end of the day I only get two options either excitatory or inhibitory now they go on to tell you about the two types of summations and I don't really test you on those it is kind of neat how they do it so temporal summation is one or more and they're rapidly firing so a whole bunch of right excitatory postsynaptic potentials that come in spatial summation spatial summation is when a whole bunch come at the same time so not like one then another another and another and another and another like the temporal one but one after another and then spatial just means let's just all go in together so let's just warm rush them either way either way summation means I'm adding those excitatory events so epsp is excitatory post-synaptic potential ipsp is inhibitory postsynaptic potential I promise you you'll see those again okay now this is what we've seen already comparing a great - an action potential graded potentials dissipate right when they try to travel away from the place where they were initiated so they're localized and action potentials can propagate or move away from their initiation site and never lose their strength and then once we get an action potential it's all or none right if it's sub-threshold I don't get one if I get to threshold I get my action potential and an action potential is an action potential is an action potential in the nervous system an action potential is a nerve impulse okay so again just those comparisons that I just told you right there and now we're gonna talk about the neurotransmitters so I'm going to tell you specifically that there's about five so there's fifty or more but there's five of them that I'm gonna expect you to remember not that they're gonna necessarily be on this test but they will come up again later and I want you to hold onto them so we can classify them by their chemical structure or by their function function acetylcholine acetylcholine we already know its release at neuromuscular junctions right it stimulates or excite skeletal muscle that's the contraction we also know that acetylcholine is degraded by its own specific enzyme acetylcholinesterase so you have to know that one because we've already learned it right so acetylcholine is one that you have to know now in general in general I take the catecholamines and I explained to you how adrenaline is in there so dopamine is in there and adrenaline which is epinephrine is in there and the only reason why I'm gonna bring up epinephrine because you will see that one again I promise but epinephrine is there in dopamine and the reason why I'm bringing up the both of them is that they're both catecholamines but I want to explain something to you I want you to know that we have done research and we have realized that people who are adrenaline junkies the ones that are seeking those risky things to do to get their adrenaline pumping most of the time they are dopamine deficient isn't that crazy like there's a correlation so they have a decrease in one of the catecholamines dopamine what they do then what the brain does to help them exhibit the same effect they go and do something risky to get their adrenaline pumping that to me is cool so we have acetylcholine that you have to know dopamine and epinephrine epinephrine being adrenaline more people are are familiar with adrenaline you get your adrenaline pump in your heart rate goes up your pupils dilate your respiration increases your sweating right adrenaline and then I dolla means the only reason why I want to mention one specific ID Alamein is because I mentioned it already and that's serotonin serotonin makes you feel good and here it says that imbalances of the I doll amines are associated with mental illnesses and that's a big deal because again I mentioned it with the selective serotonin reuptake inhibitors SSRIs are a group of antidepressant drugs antidepressant drugs so serotonin right imbalances of serotonin are associated with mental illness and depression is classified of course as a mental illness so now we have excuse me acetylcholine we have epinephrine which is adrenaline we have dopamine we have serotonin right now the other one that I want to give you where there's two more is glutamate and GABA glutamate is almost always excitatory and gaba which is gamma-aminobutyric acid so gaba is almost always inhibitory and I need you to know that so those are the what six right so acetylcholine dopamine epinephrine serotonin glutamate and GABA so six out of 50 these are the only ones that are I'm going to purposely talk about again like in the lecture and more lectures okay now endorphins make you feel good right so endorphins just so you understand morphine is shaped like our natural endorphins so morphing binds to our endorphin receptors and it helps reduce pain perception so if you've ever had any type of surgery coming out of surgery you might have been on like a morphine drip they give you this little you know clicker in your hand where you can press the button and deliver more and the reality is is that you know in your head it's limited of course but if you feel like you're pressing it and you're getting more and more fing then you feel better it's boy the mind is a powerful thing but anyway endorphins are natural pain perception reducers and when we use morphine it binds to endorphin receptors alright um let's see these are these these used to be called novel neurotransmitters and so ATP would be considered a novel neurotransmitter within that cool that ATP the energy molecules now consider that and then adenosine and I'm bringing this one up now that you have to know it but I just want to make a correlation you guys as far as college students you make up this large demographic of people who consume energy drinks and drink lots of coffee so I know adults do too but you guys do this right to stay awake and so caffeine blocks adenosine and the denison is inhibitory so adenosine makes you want to sleep right inhibitory slows things down makes you want to just you know go to sleep caffeine blocks adenosine from binding and keeps you awake so that's why right there's caffeine in you know coffee and caffeine in sodas right so people take those monsters right which i think is mountain dew people and then they take those 5-hour energy shots and there's caffeine and those right so caffeine blocks adenosine receptors a dentists in this inhibitory so you're blocking inhibitions which means you're gonna stay awake then there's other ones like so again classification these are gashes one so Gasol I'm transmitters like carbon monoxide I'm only gonna bring up carbon monoxide again not just I'm not putting it on the test I'm talking about the other five but I'm gonna bring up carbon monoxide on purpose because in my lectures I like to apply real-life information right to all of this you know detailed stuff I want to apply it to something to help it makes sense to you so carbon monoxide is inhibitory and I felt like you should know this because a person who has carbon monoxide poisoning like in their home that odorless and invisible gas that seeps into the home the person falls asleep and dies they never wake up so carbon monoxide is inhibitory it inhibits everything the ability to go into cardiac arrest or respiratory arrest has to do with in habitable tracting right smooth muscle cardiac muscle their contracting and when we inhibit them right they stop working so when we talk about a person having a heart attack right versus you know having cardiac arrest it's different a heart attack is usually because of the vessels that are associated with the heart so coronary vessels they are constricted or blocked which prevents oxygen delivery to that part of the heart so myocardial infarctions is what we call them cardiac arrest stops the heart that's how Michael Jackson died that's how Prince died from cardiac arrest okay anyway so those are again neurotransmitters and remember neurotransmitters only have two options either excitatory or inhibitory and then I bring this up because we're in this you know this whole thing where we know that there's medicinal marijuana there are dispensaries there it's big money I guess you know to be made out there the idea is that we have endocannabinoids endo means they're part of us right we release these on our own and so these act on the same receptors as THC which most you guys know maybe you know is the active ingredient that's in marijuana we know that people who have glaucoma can be prescribed medicinal marijuana to relieve the intraocular eye pressure so there's so much pressure on the inside of their eye because of the build-up of this aqueous humor which is fluid that it presses up against their optic nerve and it could actually cause them to lose sight so the THC decreases that intraocular eye pressure we also know that THC active ingredient marijuana can also help with nausea so people who are on chemotherapy could take the THC or the marijuana they don't have to smoke it you know there's pills of course you guys probably know that as well but anyway I'm a proponent for medicinal marijuana because I know that it has and can have positive effects the smoke itself though is highly toxic I've seen reports that it's like six times as toxic as cigarette smoke so that's why I mentioned the pill form but you also probably know and let's just theoretically say that you know this not through any type of personal experience but people who smoke marijuana say that they get the munchies afterwards because it does you know send signals for their appetite through to the hypothalamus and one of the ways that it can help again with patients that are on chemotherapy is that it can block the nausea and it can increase their you know desire to eat okay so again neurotransmitters how have how many effects to either excitatory or inhibitory excitatory occurs from depolarizations inhibitory occurs from hyper polarizations this is gaba which i mentioned when we talking to talked about it earlier it's one of the six usually inhibitory I will tell you that persons who experience seizures because they have epilepsy they are in a state of heightened excitability and gaba is what is in the knot gaba is in it but the pork acid which is an active ingredient in anticonvulsants actually enhances the release of the inhibitory neurotransmitter gaba so gamma amino butyric acid so we can use the release of this to help control excessive excitatory events like seizures and then glutamate is usually excitatory which again I talked about acetylcholine and here's a nice little twist I kept saying specifically that acetylcholine was excitatory in skeletal muscle and that's because we learned that already but acetylcholine is actually inhibitory in cardiac muscle so acetylcholine can act differently depending on the receptors that it binds to on those target cells if it binds to cardiac muscle it causes inhibitions like cardiac arrest as I mentioned earlier if it binds to skeletal muscle it causes excitation which is skeletal muscle contraction and then direct versus indirect if it's direct I'm opening up the ion channels so neurotransmitter binds to this receptor opens up ion channels if it's indirect it's going through a second messenger system and second messenger systems are like running relays I'm not sure how familiar you are with track but in track you have a goal right and let's say it's the four by one your goal is to get around the track one time the fastest that you can but you get four people doing it the first person has a baton travels a distance and passes the baton to the next person that next person right travels his distance or her distance passes the baton the third person then travels his or her distance and then passes it to the last person who finishes the race indirect actions of neurotransmitters are relays it goes from one thing to the next thing to the next thing to the next thing to the next thing if it's direct neurotransmitter binds right to the membrane opens up ion channels and we get the effect either excitatory or inhibitory okay and then they just show you things that should look familiar chemically gated ion channels so all it says is that it's closed right ions can't go in until the ligand in this case neurotransmitter binds when it binds it can change the flow of ions across the cell's membrane one or two things can happen depolarize which means it goes from negative to positive or hyperpolarize which means that it can go from negative to more negative it depends on what these ions are right if they're negatively charged or positively charged and then the g-protein ones these are the ones that are the indirect these are a lot more complex and they happen slower and it's prolong because it's got to go from one thing to the next thing to the next thing to the next thing to the next thing and all it's saying here is that these caused widespread metabolic changes to take place because remember we're looking for in effect and then things that shouldn't surprise you at all right is that when the neurotransmitter binds and goes through the relay things that can happen is we can open or close ion channels surprise surprise we can activate kinase is kinases are enzymes that have the ability to phosphorylate things so when we've activate those kinase is then they phosphorylate that means put phosphates on channel proteins and we know channel proteins allow things to be transported across the cell's membrane and then they can also activate genes or induce protein synthesis so making a specific protein so this is the indirect mechanism of neurotransmitters going through the g-protein coupled receptors and then direct is this one where the neurotransmitter binds directly to its receptor and causes the flow of ions you know to change in the cell alright and oh so this is the relay so this is the indirect that's what I was meeting by the relay and they're actually passing a baton as well so it binds to its receptor activates the g-protein g-protein takes a ATP you don't have to know the specificities of this but can and a cyclic ANP in this case cyclic am P is going to cost the phosphorylation so we of course phosphorylate and then that activates this other messenger and in this case they're saying what that could do is effect the entry into the nucleus and make DNA I'm sorry make a specific piece of DNA that gives us a specific piece of messenger RNA that gives us a specific protein but we'll get into that when we wait we did it it was in the cell chapter okay so nevermind that was the transcription and then the translation but anyway so this is the indirect way that neurotransmitters can work and then this right here is just again understanding that neurons communicate with other neurons right so remember the synapses so we get all of these multiple communications that take place right but it's got to be coordinated so we have the circuitry I'm going to describe and you guys are looking at diverging converging reverberating and parallel after discharge I'm going to describe them and then I want someone either one two or three of you guys that are here I want you guys to unmute your mics and tell me which one you think that I'm describing so we have the circuitry where we have multiple inputs multiple inputs that come together and give us one output so diverging converging reverberating or parallel after discharge multiple inputs that come together to give us one output anybody can be Virgin yes now what happens if I have one input and it splits and gives me multiple outputs one input splitting and giving me multiple outputs split diverging yes no I Bosley I'm not moving on it so somebody says something now what happens if I get an input and it travels down its circuitry and when it gets to the end it goes back within the system and then gets to the end and goes back into the system and gets at the end and then goes back any guesses reverberating I know right this is so easy and then here's another one I have an input I have an input and to get to my output I have paths that are right next to each other adjacent and it would be like you know being you know blocked on one Street and having to take a detour to get to your same exit in order to get to the same place you'd have to get to a street that runs parallel so as silly as it sounds right I have an input I have an input but there are parallel pathways that will get me to the same output and that of course would be parallel after discharge my promise to you is it's everything that I just said one input multiple outputs that's divergent right it splits and gives me multiple outputs here is my convergent I have one two three inputs so multiple inputs and gives me one output so they came together to give me one that's convergent reverberating I travel through the pathway and at the end I go back within the pathway travel to go back in the bath with travel through go back in the pathway travel through reverberating so it goes back in its chain of neurons this is parallel after discharge here's my input here's my desired output and I can go in this direction or I could take a pathway that's parallel and still get to my output or another direction that's parallel or another direction that's parallel and still get to the same output so parallel after discharge and guess what ladies and gentlemen that is the end of the nervous system well the intro to the nervous system lecture