hi everybody I am so excited that you guys can finally see me when we do these lessons Um this is the new format of the live lessons You can see me Um I can see the chat alongside which means that if you have any questions during the session then don't forget to put them alongside I can see those Um there's a small delay in the video which means that it takes roughly about 30 seconds for the chat to update So if you feel like I've moved on and you've asked a question and I haven't answered it yet it's because I will see it It will come up on the side So don't worry I will get to you Um a couple of things Um I am streaming so if you are a little bit blurry or I look a little bit blurry it might be just your streaming settings on your side So if you want to have a clearer picture of me just make sure that you are watching me in the highest definition possible for your device Um and yeah what I'm going to do is I'm going to do an introduction to the nervous system today It is just an introduction We're going to go through the main structures of the nervous system We're going to go through um if we have enough time the neurons and if we have enough time maybe even a reflex especially if you haven't learned that just yet in class I'm going to help you out with that as well And yeah if you missed this live lesson don't worry there will be more I know that we are um going into exam time now and we need a lot of revision And so what I'm going to be doing is popping up polls for you on the members um community page And I would love for you guys to let me know what you want me to cover in those um lessons because every school does um the order of topics differently So some of us maybe aren't doing the nervous system right now We're doing evolution we're doing something else So you let me know Um and the last thing I want to say is remember if you are a member you can get access to the cheat sheet for free You just need to be a rescue member and you simply put in um your uh request and I approve that and then you have access to that Okay So let us dive into the lesson I am going to share my screen now and minimize myself down And I'm also going to show you a really cool thing that I am working on right now which is this little board that you can see alongside up here Now this is actually a infinity board which means that um I'm going to actually make one giant summary note on the screen for you now And what's really cool is that I'm going to super zoom in to one particular section over here and I'm going to talk about the nervous system and give you a bit of an introduction So let's dive in and don't forget you can at any point put a question alongside in the chat box Okay so let's dive in So the nervous system what's important to remember is that the nervous system is broken down into sections And so the nervous system if we break it down into its first component let me make my screen a bit smaller There we go If we break it down you have the central nervous system And then on the other side we have the peripheral nervous system Oh the nervous Okay Now remember that the nervous system is responsible for alerting you to sensory experiences So in other words seeing and hearing and tasting and touch So it allows you to sense but it also is linked to things like movement balance equilibrium and responding to the environment Because remember this section technically in your textbook will say something along the lines of like how we respond to the environment So the nervous system is one way we respond to the environment The other way is the endocrine system but that's another topic for another day And so the nervous system has two ways in which we respond to the environment depending on what we're using to respond So the central nervous system is broken up into two components It's made up of the brain and it's made of the spinal cord Now a lot of people don't realize that the spinal cord is an extension of the brain It's part of the brain It's not a separate um structure And we're going to go through the structures of the brain shortly You can kind of see at the bottom of my page here Now I'm going to have a little uh brain diagram that we're going to label But then if we go on to the peripheral nervous system and I I move this over to the side here and actually let me move around There we go So the peripheral nervous system is divided into two parts Now one of them is called the somatic nervous system And the sematic nervous system refers to all the other nerves that are responsible for your let's call them um choice responses So they're not things that you um do automatically Uh for example something under the sematic system would be like walking bending your arm moving And so the peripheral nervous system is made up of all of the nerves of the body that are not in the spinal cord and that are not in the brain Okay so they're all the other nerves of the brain excuse me of the body And of that you get the sematic branch of the peripheral nervous system and you get the autonomic Now as the name suggests autonomic means like automatic These are all the automatic responses of the human body And the autonomic can actually de be divided again into two parts Um and when we think about it there are two divisions of how you can respond right and that's going to be the sympathetic and the par sympathetic Now what do those two divisions mean the sympathetic nervous system is what you know as the fight and flight And so I'm just going to put that in here the fight and flight And that's like all of your responses to the world around you that require like quick immediate reaction and that things that are going to like save your life Whereas parasympathetic is also known as the rest and digest which is pretty much probably what you're doing right now as you watch this video You're at rest You are now in your parasympathetic nervous system So just to recap something just in case it's not clear when we started this particular section The nervous system is broken into two main components right the central nervous system which is made up of your brain and your spinal cord Okay this is like head office These are the organs that do the main decision making jobs right but then the decision-making jobs need to be carried out and that's where the peripheral nervous system comes out These are all the nerves outside of the brain and the spinal cord and they're going to carry out the decisions made by the brain and the spinal cord Now those decisions that are made can be seatic which means body It means things like moving things that have a choice like I want to walk towards a point That's a sematic choice That's a sematic nervous system movement Or it can be autonomic which means you don't think about it It just happens What kinds of things can you think of in your body that just happen for example if we have the sympathetic nervous system the things like blinking when someone throws something at your face or your mouth drying up when you're nervous that's all the sympathetic nervous system in your fight and flight And your parasympathetic nervous system is your rest and digest So all your automatic functions like breathing and digesting and sleeping and and and just being at rest all of those automatic functions are controlled by the parasympathetic nervous system Now before I go on to any more and I do want to dive into the structure of the brain So I'm going to zoom all the way in over here We are going to go through the main structures within the brain now And I'm only going to focus on the ones that you actually need to know because a lot of people don't know that there are many labels and textbooks and things that you actually don't need to know And if you use your exam guideline carefully you will actually realize that there's about I'd say five major structures that you actually need to know and their functions Otherwise there's no need to go into any more detail Now if you do have any questions don't forget to pop it alongside in the chat and I can see them and so I'll be able to answer you Now while I wait for you to put in your questions I'm going to go through the main structures within the brain This is a cross-section through the brain So if we take a step back we are going to go through the structures of the central nervous system starting with the brain right and the brain has been uh cut in half here There's a cross-section here And what we're looking at are the major structures right so we're going to start off with the first main label over here which is this whole kind of gray structure that you can see on the outside That is the cerebrum And I want you to think of the cerebrum is a place in which you think and where you have memory and where you sense So when you think of cerebrum think of memories think of your senses and also think of your consciousness That's where you live You live in that part of the brain the gray part of this diagram Now another important structure that you have in your brain is this lower region over here which is called the cereabellum Now the cerebellum has a really important job Its job amongst other things is it is responsible for actually keeping you alive So one of its most important functions is that it maintains your heart and your breathing It does a couple of other things um which are things like for example I'm just going to move this up a little bit which are things like balance um and something called muscle tone And so when I talk about balance I'm literally talking about the fact that your ears are responsible for keeping you balanced But how does your brain know that you're balanced well you tell the cerebellum that you are balanced or not So your ears are constantly communicating with this back region of the brain And when I say muscle tone it doesn't mean like you're toned like your muscles are toned What it actually means is are your muscles engaged and the easiest way to understand what that means is when you go to sleep you lose all muscle tone Okay when you wake up you regain muscle tone And the reason for that is you don't want to act out your your um dreams right so you lose muscle tone when you go to sleep So when you go to sleep your some of your cerebellum switches off so it can rest okay but not all of it cuz remember it maintains your heartbeat and your breathing Right then let's move on to the next important structure Now we can't see the whole thing here but I want you to know that this pink section coming out the bottom here is the spinal cord And obviously it will go down the full length of your vertebra and your vertebral column And then sitting just above that do you see this like first little bump right there's a bigger bump over here but I'm not talking about that one I don't want to talk about that one We don't need to know that there's like this first little bump And that first little bump everyone is known as the medulla oblangata You may have heard of that before Yeah Um and the medulla ablangata is this very very important region that is also responsible for your breathing It's also responsible for things like um uh your reflexes and less important reflexes like for example sneezing and things can also come from this region It's a really old part of your body in the sense of its like age right so um it is such a vital section of your your your whole nervous system And so I'm also going to put here that it regulates your heart beat and breathing So it does work with your cerebral Okay they work in like tandem with one another And then another important structure that we need to know is inside the brain And there are two important pieces Now the first one is this large kind of peachy structure over here This is called the corpus which just means body by the way It's not like a corpse like dead Corpus just means um body And you say colossum Okay The corpus colossum What is its job well it's a it's a dense bundle of connecting tissue And the dense bundle of connective tissue connects the right and left hemispheres And what is a hemisphere well the brain is divided into two a left and a right hemisphere And so the left and the right control opposites in the body because of the corpus colossum You see what I'm trying to tell you is your left side of your brain controls your right hand and your right side of your brain controls your left hand and your left side of your body And that is because of the way the corpus colossum crosses over at the back of your of your brain You can't see it in this picture but it crosses over and it goes down your spinal cord and into your spinal cord And that's why there's like a a cross uh uh connection And so that is what the corpus colossum is And then you'll see um sitting just underneath it Let's see if I can squeeze it in over here This over here right this little space here is called a ventricle Now you might remember a ventricle from the heart right and it's not too different from an actual ventricle in the heart in the sense that a ventricle just means like a a cavity right a space And the ventricles are there for um safety They are there to cushion They are there to uh protect the brain And so a ventricle is filled with cerebral spinal fluid And that fluid everybody is the fluid that creates like a protective cushion on the inside of the brain So every time you knock your head forward or you knock it sideways there's like almost like a fluid like an airbag on the in the middle of your brain so that the one side of the brain doesn't knock into the other side of the brain Then it knocks into the skull Okay so these are the main components of our brain and their main functions But now how do we protect the brain right because this is a really important organ Okay this is where all decisions are made This is where I keep my memories This is where I sense things How do I protect the brain and also the spinal cord well we're going to have to zoom out here and we're going to have to make our way over here to this diagram Now if you're uncertain as to like what I've zoomed in on here this everyone is a cross-section through the top of the brain and there's a little bit of skull there and some of your skin Now when we are protecting the brain we are going to use membranes to do that We also protect the spinal cord with these same membranes So I'd love for you to remember that as well And in this picture you can't see the bone around your spinal cord which would be your vertebrae Oh I've lost my light Or you won't be able to see the full skull in this picture but you can see some of it So let's just pop a couple labels on here This is a cross-section through the top of your brain and through the top of your head And so this over here would be skin And then just below that you can see the bony layer there is the skull So the skull is the first protective layer around the brain right but then we've got three protective layers or three protective um membranes that sit just underneath that to protect you and to protect your brain And the first layer is this pale blue layer that we can see sticking out over here It's the first layer just under the bone that is called the jura martr and the jurora mater as the name suggests is quite durable It's quite thick Um if you ever have brain surgery or you become a neurologist and you actually do surgery on people and you you cut through the skull you will notice it's it's actually quite difficult to see the brain because there is this thick bag like this bag like structure around your brain and it's the dura mater Now the duramater is followed by another layer because one layer will not do And that is going to be the arachnoid And the arachnoid is this kind of it looks kind of green um and kind of like long like uh tendrils and fibers And what the arachnoid is are all of the little teeny tiny blood vessels that are providing blood to the surface of the brain Okay And excuse me And finally this green this green layer the actual layer touching the the brain itself that is called the pia ma excuse me Now the pia mater is the final protective layer around the brain And these three layers together So let's let me change my pen color if I can Let's see Can I oh no I'm going to stick with the black I'll stick with black I'll stick with black So we've got one two and three Those three layers together produce a protective collective structure called the men's And may I add this was a word they asked last year in the final exam And I felt like when I put this in my prediction video everyone lost their minds because they're like I don't know what it is I don't know what a men is A men is a protective membrane around the brain and the spinal cord as well Okay So you can get these three layers in the same order sitting around the spinal cord Okay So once again I'm going to take a little quick break as we move around on our picture And I want to remind you if you have any questions for me um or if you want any clarifications as I move along please let me know and I will do that for you Um and obviously it comes up on the chat that I can see that But um if you have anything let me know What I want to do next is I want to introduce you to some smaller components Um and I also I want to be able to maybe touch on the spinal cord as well today because we've done the brain right and we've done the menes but um I think if we get that far which we might not be able to do a reflex today but um maybe I can introduce you to the spinal cord just before we go I think let's do the nerves first So I think that's a better one Okay before I do Kishny has a question Please explain what is a pia ma So the pia ma I'll just quickly go back here That one there Okay Uh this is this one over here that we're referring to The piam ma is the innermost meny So it's the innermost membrane And uh like the other menes around the brain it's its function is to protect um our brain and it is the soft inner layer So if you were to classify the three layers the pom mater is the soft inner protective layer Then you have the arachnoid which provides um blood vessels and blood to the area And then you have the juror mater And the jura is the outermost layer It is the most dense and fibrous layer and it provides um the first like line of protection before the skull Grace wants to know how in depth about the menes do we need to know you just need to know their names and the fact that they provide protection That's all you need to know Um Brooke wants to know any textbook recommendations alongside my study guide I personally at school use um for the life of me I cannot remember who makes the book but it's that purple book It's a purple um textbook I think it's the mind action series and that's what I personally use And there is some flaws in it like there's some things I don't love about it but out of all textbooks that is the one that I like most And if you watch some of my oldest videos on YouTube it's actually the book I use to teach some of my very very early on lessons when I was doing it back during lockdown Okay So I hope I've answered some of those questions for you Um I think to make it make sense because I want to marry all this knowledge together I think I'm going to just quickly run over the spinal cord before I get to neurons because I think maybe I'm going a little bit too fast here So if we go back to our little diagram over here we have done the central nervous system first and so we've covered the brain structure right now we need to cover the spinal cord structure And so we're going to do the basics for now We're not going to get too crazy You do need to know quite a bit of detail about um your spinal cord And so please don't please don't ignore it when you when you study and you prepare for your exams Um a lot of students do and then they realize oh shoot I need to know a lot more than I thought Now for now what I just want to focus in on is what is inside the spinal cord So what you're looking at here is a cross-section through the spinal cord And you are looking at two different colored matters And so the brain is exactly the same It's also made out of what we call white and gray But um they are inverse or they're swapped but I'm getting ahead of myself Let me label it and I'll show you what I mean So first of all if we look at this this is the cross-section of our spinal cord And uh one of the most common questions I also get is ma'am how do I know the top of the spinal cord like how do I know that's the top and that's the bottom what happens if it's like upside down in an exam okay So when you are looking at a spinal cord diagram do you see this like little cleavage space that it's being created here that is always on the inside of um the spinal cord In other words the inside of you So this would be the top or the back of you like your your back your actual back behind you That will be behind you That's the top And this is technically the bottom or the inside of you like on the inside of your spinal cord closest to like all your internal organs Okay Now we've cut the uh spinal cord in half in this picture And there's a couple of things that I want to label for you First is this like brownie colored matter on the outside is actually called white matter And white matter is uh white because it contains something called myelin And I'm going to get back to what myelin is now soon Um and this is also why it's difficult for me to make up Do I want to teach you neurons first or do I want to teach you the spinal cord first but we'll do the spinal cord first So it contains a lot of myelin and myelin is fat basically and that's why it has like a white color to it cuz it's mostly fatty And the white matter also contains a large amount of sensory and motor neurons And I'm going to tell you what a sensory and a motor neuron is before the end of this lesson today So that's what the white matter is That's what's inside the white matter It's fatty So it has this white appearance And it's got a lot of sensory and motor neurons So sensing and moving nerves and neurons Then you will notice we have this darker gray matter on the inside Now the gray matter is really important because this is the part of your spinal cord that's going to do a lot of um decision making Okay and who's making the decision well it's mostly made out of what we call inter neurons Again I'm going to introduce you to who they are today and then I'll come back to this picture and link them together And the reason why it's gray is because it lacks the myelin So it lacks myelin is there's there's none there And it all has to do with the purpose of inter neurons and the fact that they don't need the fat Now there are many other reasons why gray matter is the way it is for example it is there for um primitive reflexes and integrative reflexes But I'm going to get back to that at a much later lesson not today because there's a lot more that we could cover there Now the one thing that I do want to cover which I didn't explain at the beginning is if I just quickly go back to our men and picture where are you men and gies there you are You will actually notice if I go nice and close that the gray and white matter have actually swapped locations You will notice that the white matter is on the inside and the gray is on the outside And so that's an important difference between the spinal cord and the brain that maybe you should note that you didn't know Again why is that the case ma'am that is the case because of what the brain does versus what the spinal cord does And the matters the colors indicate the function because you want a lot of gray matter versus white for different functions And then you want more white than gray so that you can do a different function as well It's all about their functions And I think maybe it'll be a bit easier once I've now covered neurons And once you understand what a neuron is and where that myelin that fat is it'll make more sense why the brain has it the other way around to the spinal cord and why there is more gray matter than white matter in the brain And in the opposite in the spinal cord there's more white than there is gray So if we kind of zoom out for now and I just want to give you a little overview of our spinal cord because we're not done yet You will also notice that there's this little central canal down the center here Central canal Um it's also filled with spinal fluid If you want to use the full name you can which is cerebrros spinal fluid Again what is the purpose of cerebrros spinal fluid it is for a cushion It's the same fluid inside your brain as a little airbag right and then what you have coming out of it you can see this like little extension on the side here This little extension here And you've got one here as well These I'm going to join them together for now We are just going to call these spinal nerves They actually have more specific names but I will only do their specific names when we start to do reflexes which is not in today's lesson We'll need more time for that So if we kind of zoom out here now we've got a rough idea of what our spinal cord looks like And um if I try and get everybody in focus at the same time for now you can see we've done an introduction to the nervous system the brain the menes you can see the spinal cord and the final component which we haven't tackled yet which will be the last thing that we're going to cover today are the uh neurons And so the neurons are the smallest functional component of your nervous system And so once again if we now refer back to our original diagram of how the nervous system is broken up we've done the brain and we have done the spinal cord structures right but now how do we get the information from the brain and the spinal cord how do we get it from there and send it to the peripheral and also the other way how does the peripheral tell the nervous system what's happening with the body well that is where neurons come into play Neurons are cells right they are nervous system cells And there are three main kinds we need to know I would also like you to know the following things Number one you will have to be able to identify these neurons just by looking at them in an exam without labels without any guidance You're going to have to know what these three are And I'm going to show you the easiest simplest way to tell the difference And then we'll go into a lot more detail of the actual structure So let's begin with the three kinds of neurons that you get The first kind you might be more familiar with because it looks familiar is a motor neuron Right so this is a motor neuron and its main function as the name suggests is movement Now you find these a lot in your muscles and the glands of the body and that's because motor neurons are found inectors of the body So like places where you need to carry out functions and so the motor neurons do that Now how do I know a motor neuron is a motor neuron well you are going to look for this big green swollen section called the cell body When the cell body is surrounded by these little branches here called dendrites you know you are looking at a motor neuron because the cell body is surrounded by the dendrites And now if you look at the other two you can see that there's a clear difference Motor is the easiest one to identify It's the next two that a lot of people have trouble with Okay the next one our middle one is a inter neuron Now the inter neuron um is a neuron that is going to be found mostly if not exclusively um in the spinal cord and in the brain So if I first of all if I write what its function is the inter neuron is for intergrative function You see how their names are kind of linked to what they do Um integrative means thinking and choices That's what it means And so an inter neuron is there to integrate information It's to take the information in and make a decision And where do we find it well we mostly find it in the brain and the spinal cord That's its main location Okay Now how do we identify it once again we look for the cell body And do you see that the cell body is off to the side here it's got this little extension here That is how we know we are looking at a inter neuron Now last but not least and these two are the ones that get confused So inter neurons get confused with sensory neurons Once again as the name suggests which I think we all are going to guess what this one does This one is where all of your senses are interpreted or brought in And so your sensory neurons are the neurons that are connected to the senses or the sensory organs like the eyes the skin the tongue and the mouth for taste your ears for hearing And so sensory neurons collect the sensory information and they send it through to your brain And so we find those in the sense organs We also call the sense organs the receptor organs That's the more formal name for it Now there's actually an order of um operation here This is the last thing I want to do before we do a lot of detail on the neuron structure And what I mean by that is these three neurons work together with one another and they send information from one to the next in order to communicate So let me take a step back and say this Let's say I want to feel this pen in my hand And I want to feel it Now the feeling of it my fingers touching it that is generating a sensory impulse through a sensory neuron in the skin of my fingers So I can feel this pencil or pen that I'm holding Now that has to travel all the way to my spinal cord and to my brain So information often flows from a sensory neuron to an inter neuron And an inter neuron either in my spinal cord but in this case in my brain is going to receive that information and it's going to integrate it meaning oh wow that pen feels smooth it feels cold to the touch and it has all this information that it is working with to determine what I'm touching Right but now let's say I want to move the pen around while I hold it Now I can hold it and I can feel it but now I want to move it Now the inter neuron will make a decision It will say well we're touching this smooth pimp but we want to move it It then sends an in piece of information an impulse from the inter neuron to the motor neuron And the motor neurons and the muscles in my finger allow me and my wrist allow me to move the pencil around And it's communicated with one another Now you will notice it is a one-way direction Um it doesn't have to be in my picture uh from right to left But what it is important is that information is always going from the senses to the inter neuron which is in the brain or the spinal cord and then over to the motor neuron Now it doesn't always have to get to the motor neuron In other words there could be a break here where it just gets to the inter neuron because do you agree that you don't always have to move you don't always have to um uh react Some things you're experiencing like senses you don't have to do anything like listening to me right now Your sensory neurons in your ears are hearing what I'm saying They're transmitting that impulse to your inter neurons in your brain Your inter neurons in your brain are interpreting that information and hearing me right now and understanding the words that I'm saying Do you have to move no So you don't always have to go from sensory to inter neuron to motor You'll only go to motor if you need to move Now I'm going to take a quick breath there and I'm going to ask if there are any questions on these three main kinds of neurons Um if there isn't I'm going to go into the structure or the basic structure of a neuron because for now all I've done is just identify them and show you how to identify them which oh by the way I haven't told you about sensory neurons Let's do that one quickly Sensory neurons have their cell body as you can see right in the middle of themselves like right in the middle there And this is a tricky one because I haven't taught you yet the structures yet But what you find is that the cell body is inside of something called the axon Whereas on our inter neuron over here it's sitting off from the axon like to the side there But once again don't worry I am going to go over the um cell bodies and the axons and like what are all these things because that's going to be our last little bit for this lesson today But if you don't have any questions on the neurons uh don't worry about it You can also leave comments on this video because once we finish the live it gets uploaded immediately and you can leave me questions and I can reply to you Okay it's another benefit of being a member because when you comment I do get a notification Okay Brooke has a question Will the inter neuron and sensory neuron also have dendrites yes Yes they do Okay And so I haven't drawn them in here or labeled them but these over here are the dendrites So those are dendrites and these are also dendrites on the other side So they do also have dendrites Yes And the motor neuron also has axons in the same places So axon is here and here and there So they also have axons as well It's actually all about where the cell body is That tells you where the dendrite and the axon is But I'm going to do that now for you I'm going to label that for you Okay So maybe this will also help Brooke Let's go over to this lovely picture here Now this everyone is a motor neuron I chose it because it has everything in it and it's the most common picture that we see in um exams and tests and textbooks It's also the easiest neuron to identify and it's just lying down on its side Okay don't be don't be worried that it's not the other way around Okay so let's run through the major structures in our neurons and these are all the structures that you need to know There's about six of them and I'm going to start from the top Now over here these branchy structures are the dendrites I've already introduced them to you and yes all neurons have dendrites I just want to have a quick read There's a question from Keshny How will they ask the questions of neurons in the exam and will we have to draw them okay so yes you will have to draw them You will have to label them and you will have to identify them with reasons So how do you know this is a motor neuron how do you know this is a sensory neuron how do you know that this is an inter neuron then they could ask you what is the function of a dendrite what is the function of myelin what is the function of a um axon okay so to summarize how will they ask the questions on neurons one they will ask you to draw them or label them So that's two They will ask you to give the functions of all the structures They will ask you to identify them like which one is which and when you identify them how did you know it was that one Okay lovely All right So the dendrites they're at the end there they're multiple branches Now sitting just below that this whole swollen region and I'm going to make this a long label here is the cell body And the cell body if you look at my diagram carefully has some familiar structures in it You see this round purple structure that's the nucleus And if you look very carefully you can see some mitochondria You can see some ER You can see some goli body So the cell body is essentially like the main part of the neuron of that cell Now let's move down This whole section this whole thing and this is really important everyone This is an axon Both the straight part and the branchy bit at the bottom That's all an axon That whole thing And a lot of people get a little bit like flustered because they're like "But but dendrites are just the branchy bits on the one side Aren't those also dendrites at the bottom here with the little knobs?" No no no no no Everything from the cell body down is an axon Okay that's all an axon And the purpose of the axon is to conduct an impulse and to conduct it to the next dendrite of the next neuron Okay but I'll I'll get to that Okay let's finish labeling it and I'll put all the pieces together The next thing I want to label for you is this outer layer Um and that is the myelin So if you were wondering where it is this is the myelin sheath It is a fatty layer and its purpose everyone is to speed up impulses and to contain impulses Um so I want you to think of it as an insulator You know like with electrical cables you always have like plastic or rubber around them to prevent you from shocking yourself Myelin does exactly the same thing It just makes sure that the electrical charge is is inside the neuron at all times Okay so it's not going in places it doesn't belong So that's where the myelin is And so if you don't have myelin like we mentioned earlier with the white and gray matter you will be gray If you have myelin you'll be white Okay uh Hamida asks "Does the inter neuron have a body cell?" Yes it does I will go back again and kind of put all of this together for you so you can see how it all links but it does Okay Um so the mile and sheath is on the outside Then what else have I gotten not gone to oh yes these So what are these knob things on the end here and like what is their purpose so they are called a sinaptic knob Okay knob And essentially the syninaptic knob is um where one neuron is going to transfer an impulse to another neuron So let me draw it so you know what I'm talking about Let's move this picture over slightly I want you to imagine okay that there is another dendrite another neuron sitting here So there's a dendrite here's another dendrite and they're all coming together into a cell body And so there is I'm just going to go around that There is the nucleus of the cell body I wonder if I can get rid of that No my razor is not erasing And then it goes down And then there's your myelin sitting on the outside again just like my other one Okay And if I move it over slightly it'll go down down down down More myelin And then it will branch out again with more synaptic knobs on the end All right so it's like one neuron hovering really close to the other So the dendrites and the synaptic knobs or the psychaptic terminals that's another word for it They never touch They're like really really close And you can see I didn't make them touch If we zoom in I didn't make them touch There's a space there And let's actually close them off like that they don't actually touch Okay and so what happens is if I zoom out a little bit so we can see the one neuron going into the next What happens is an electrical impulse is going to travel down the dendrites down the axon down the synaptic knobs Right it's going to jump to the next neuron and it's going to travel down that neuron's dendrites down its axon to the synaptic knobs and then it's going to get to its final destination And that destination being potentially um your uh muscles you know moving You're going to contract the muscles You're going to move them right now How do we put this all together and we're going to answer Hamida's question about the cell bodies and neurons and putting all these pictures together So if we have a better understanding of like the neurons themselves if we go back to this drawing over here once again we can look at the cell bodies So they all have cell bodies They are these green regions here and I have labeled all three of the cell bodies You will see they all have cell bodies right all of them They're just in different locations Now the final thing that I want to point out to you is as I mentioned they all have cell bodies They all have dendrites They all have axons The key which a lot of teachers don't know and I would love for you to all remember this because I think your teacher would also be impressed if you knew this before she or he taught it was where do the dendrites and axons actually begin and end okay So let me show you something If we look at the motor neuron everyone the dendrites are all around the cell body Those are the dendrites But everything from the cell body down is the axon Okay pay attention to this part please This is important If we go to the inter neuron however everything before the cell body everything I'm circling here now everything there is a dendrite everything after the cell body is an axon so the cell body indicates what is a dendrite and what is an axon on Let's do it to the last one on our sensory neuron Everything before the cell body dendrite everything after axon And if you know that I'm pretty sure your teacher will be really impressed because a lot of students don't know that's fine detail and it is really important Why is it important well we're going to have to leave that for another lesson because that is going to go into reflexes and how electrical impulses move through your body through your neurons and how your neurons actually do their job Now once again we're going to wrap this lesson up and I'm going to say goodbye If there are any questions for me please don't forget that you can of course leave a comment for me um down below in this video Um and I I will be having more of these lives as we get closer to exams And also just a little punt for those of you who are still here watching this video I have made a whole university application series that I also think you guys should go and check out It's about how do you apply for university how to prepare for NBTs how do you um you know fund your university experience and also if you chose Mathlit what can you study with MASLIT and there are some uh other videos that are going to be coming out that a lot of you are going to be interested in especially if you've taken life sciences as you probably have and what can you study with that um before I go I'm going to do one last question from Shayon which says "When studying for this section for finals do we only need to study what's in the exam guidelines?" Yes yes yes yes yes yes A lot of teachers expect you in your prelims or your mock exams to know a lot more than you actually need to know It's important that the guideline tells you what you need to learn That's exactly what you need to know And the final will only test you on that information And so you don't need to study all that other stuff Um and when I say that other stuff it basically means sometimes uh some teachers want you to know a lot more detail than you actually need to know Um and lastly I also want to point out if you if you are a rescue member and you have access to the study guide the cheat sheet I also have used the exam guideline to write that And so everything that's inside of that um study guide is exactly what you need to know No more no less That's why it's only about 130 pages And that's so it can be simplified for everybody so that you don't have to unnecessarily study stuff Okay I'm so glad that you enjoyed this lesson today If you've missed anything and you want to watch it again obviously this will be uploaded And of course don't forget to make sure your notifications are turned on so that you get notified when I go live next and when I post for it And I will see you all again soon Bye [Music]