# Organization of Cell Type v2

## Метаданные

- **Канал:** Neuroscience Online
- **YouTube:** https://www.youtube.com/watch?v=PoeBrtOrlJ0
- **Источник:** https://ekstraktznaniy.ru/video/34001

## Транскрипт

### Segment 1 (00:00 - 05:00) []

now you will hear more complete from dr wehrmeyer he is a professor in the department and he is one of the experts on this topic and you will enjoy here prepare you wonderful and colorful presentation please dr weymouth my area is dopamine norepinephrine serotonin neurotransmitters i've been working for about 40 years in that area the lectures i'm going to give you today is the beginning of a series the lecture is on the nerve cells and the glial cells a little more about their properties uh the glen cells we don't talk about a whole lot in the course because uh they're that's not where the real action is that we're interested in but they are very important and uh i'll talk about those today a bit and then uh occasionally during the subsequent lectures i will bring them up when important so what i'm going to do today is talk about neurons dr burn already talked to you about neurons in some detail and then uh about glial cells the supportive tissue of the cns and the peripheral nervous system as well uh have questions just raise your hand if you have it probably other people do as well so we just want to understand the properties from a functional perspective that's what this course is all about uh is the function we are going to talk a little bit about how we name nerve cells there's a number of different mechanisms that evolved over the years the nervous system has been studied beginning with cohol and other early scientists spanish for a couple hundred years and they named these cells early on just on the basis of their shape for the most part but now we have chemical ways that we can label the cells which actually are more important in terms of the function and then as i said i'll talk about the glyph cells uh as well so first to start off with nerve cell structure and properties dr byrne talked to you about four parts of the neuron we can divide this up conveniently into this uh soma or cell body uh the this is what you would uh refer to as being the what every other has muscle cells secretory cells in endothelial epithelial cells they all have the same kinds of material in them as the cell body so i'm going to talk about that first we call it the cell body or the cell soma then i'm going to move on to i don't have two on here two actually was this region right here which i'm not going to focus on today uh dr bernal talk to you about that i want to make this simpler uh than going into the axon hilla so where there's the cell soma the axon the dendrites up here was looking in the right place the axon and the nerve endings which impinge on the dendrites and the cell body itself and when those nerve endings are on to a muscle it's called a neuromuscular junction or the motor end plate they often talk about in physiology so i'm going to start off with the soma is as you know contains the nucleus in cells that are neurons there is a large amount of ribosomes and uh and rough endoplasmic reticulum that's contained in this selma and that is referred to in the light microscopic reference as to nissel substance she learned about that in histology so this region is what we call the metabolic and biosynthetic core of the neuron because neurons often have axons that project for three or four feet and lots of dendrites can go out here and cover this entire room this is a large responsibility for this cell soma so they're going to

### Segment 2 (05:00 - 10:00) [5:00]

all of the proteins that are going to be made and a large amount of the energy that's going to be necessary is generated in this structure the cell soma it contains the same kind of structures that i'm going to talk about that are in axons and dendrites later on and those are the microtubules that are responsible for the axoplasmic for the transport of proteins and other kinds of molecules we have neurofilaments there are filaments you should know are what gives neurons their structure their support they're like the bones of a body the neurofilaments they're a three protein i'm not going to go into what subunits make up that protein three protein molecule that is arranged uh in a polymerized manner to form the neural filaments so they're going to be very important in here providing the structure of the cell body and when i get when i talk about the other parts of the neuron i'll go into those there as well there is also a thing called a microfilament is made up of polymerized actin and microfilament is almost always related to the movement of either some kind of a subcellular structure or the actual uh shape of the neuron and i'll get i'll talk about that a little bit so there's only three there that we really need to worry about the neurofilaments the microtubules and the microfilaments i say and i mentioned on the slide here that there is a table which describes the details of their structure that's no longer in the syllabus so you don't have to worry about that so on the lecture next wednesday i'm going to go into the function of the rough endoplasmic reticulum the smooth endoplasmic the golgi in the process of forming these vesicles that we find in here because these vesicles are the same vesicles that are you find down at the nerve ending that dr byrne talked to you about containing neurotransmitter i'm going to talk about it again today but that's where these vesicles are formed originally we can recycle those when we get down to the nerve ending and we'll talk about that later but this is where they're formed dendrites these processes that stick out one of the things that we did in this particular course is we called what we're gonna what we the nerve cell that we refer to most of the time in terms of structure versus function we call the model neuron because neurons as i'm to talk about in a few minutes have all different kinds of structures but in order to have some place to start we just label this a model neuron and the model neuron is what's called a multipolar neuron and has all these uh cell body with all of these dendrites that are radiating out and these dendrites as dr byrne mentioned are the uh increase in the area of the neurons membrane that allows numerous synaptic contacts and so there have been estimates of around 10 000 synaptic contacts on this on a model neuron like this if it were for example a motor neuron the neuron that sends processes out to contract the muscle so there's a large amount of input here and i'll show you that in a second this then pretty much defines the shape of the neuron where those dendrites are this shows these um cytoskeletal elements that i talked about and these uh broken lines represent the microtubules and why is it appropriate to use broken lines well microtubules in fact aren't continuous there are breaks in the microtubules are made up of tubulin as you recall from your previous lectures and they form a hollow structure that has a positive and a

### Segment 3 (10:00 - 15:00) [10:00]

negative end and the movement of substances both in the uh what we call the anterograde reaction direction out the dendrite and the retrograde direction back down towards the cell soma is mediated by these microtubules again i'll talk about this on wednesday because i'm going to go into exoplasmic transport in some next wednesday in some detail then these are representative of the neurofilaments remember they're the ones that provide the structure for the neuron and then we have these little wiggles in here which are the microfilaments which are made up of actin so this is a representation of a dendrite and you'll see that we have something here that's very characteristic of some neurons and that is an outpocketing of the dendrite into what we call a spine a dendritic these have been determined to be really important in synaptic plastic in neuroplasticity synaptic plasticity over the last 20 or 30 years as they can change their shape and the lectures that dr byrne will give you uh in the subsequent days will illustrate how a change in the diameter of this spine is going to have some dramatic impact on the conduction of the signal through that particular area so and you i've placed in this model neuron slide some of these actin filaments in there because they do change their shape if there's anything else that we want to talk about here we do have i haven't drawn it in here there are some mitochondrion dendrites and there are and rough endoplasmic reticulum associated with the dendrites so what does that mean we can make protein in these areas in these processes this is not true of the next thing i'm going to talk about and that is the axon the oxon appears as if it's not capable of making any protein the region of the axon so we can make protein here and there's some theories about the biosynthesis of proteins that are associated with these different regions which may be important in the function of the of the cell so this is a slide which has been stained with a silver stain or a gold stain heavy metal stains have an interesting characteristic of only staining specific cells nobody really knows why that is but it allows us as scientists basic scientists for the most part and some clinical scientists to see the structure of uh neurons and glia if this stained everything you'd always be just black but for some reason only this particular process took up the stain and that's how we can see the structure of the uh of this particular uh dendrite these protrusions are the spines that i talked about and these uh this is obviously just one dendrite there would be you know um many more of these that we could look at this then shows uh the spine here and this is a t stands for uh axon terminal so here is a synapse that dr byrne talked to you about i'm going to go over a little bit more its structure in a second and here again s is a spine apparatus and then this is a nerve terminal here with the vesicles that dr byrne talked to you about outline that in red just to illustrate it more detail okay the axon uh it's always fairly smooth it doesn't have the rough characteristics that the dendrite has so if you're a scientist trying to understand the function of a particular neuron you can usually with a sectioned electron microscopy find out where that axon is another characteristic is that it has a very acute angle here between where the axon is and the cell body whereas the dendrites don't they're sort

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they're very gradual formation as you can see here this region here is where the spike that dr burns going to talk to you about is initiated and he'll go into that in some detail this region right here so this is the axon it can bifurcate and trifurcate and lead to many different in this particular case motor end plates that are interacting with the skeletal muscle it can also put off a collateral and synapse with another axon which will be the mechanism to have feedback and again dr burns going to go into all the details about how that works this is just a introduction to the structure the axon uh is filled with these neural filaments microfilaments and neurotubules one of the characteristics of the axon is that the neural tubules that are in the axon have a very specific microtubule associated protein a map that i presume that you've heard about if not this is a introduction to that the microtubule associated proteins which obviously are proteins that are associated with microtubules in the axon are made up of cow is becoming a very important protein if you haven't seen concussion yet you'll learn about tao there when i talk about alzheimer's disease at the end of the course i'm going to talk about tau and the characteristic that's really important is the tau that's found here it's usually only in axons in alzheimer's disease and obviously in this characteristic of professional football players where they have a increase in tau it's found in the dendrites in the and the cell body as well so this is called a tau apathy it's a it's a really important observation and it relates to what causes dementia both in the professional football players situation and in alzheimer's there's a lot of evidence that amyloid is really important in alzheimer's the reality is tau is really important as well and we'll get into that when we i talk about that at the end of the course so we i have a cross section here of showing you the microtubules that are these round they're usually in clusters we have clusters of neurofilaments and you can see the microfilaments usually located in the axon close to the membrane the axillema as we call it so that illustrates the large number of these structures that you would find in the axon so remember again these uh black dots here are responsible for the structure of the axon they give it its uh characteristic structure its shape nerve endings we have here see that i yeah the nerve endings coming in here on this particular spine apparatus and another one here where there's a spine nervin this is a modified nerve ending with neuromuscular junction all these are points at which and dr byrne called these synapses rather than nerve endings so there's the nerve ending and where the nerve ending connects to the next the cell that it's innervating is the synapse it's become generally accepted you just call the nerve ending itself the synapse so don't be confused by that so as uh we've talked about over and over now these are the site of connection between one cell and another one thing that uh has been emphasized yet and dr byrne will go into this in great detail about how this functions is that a nerve ending can either excite

### Segment 5 (20:00 - 25:00) [20:00]

the cell that it's synapsing with or it can inhibit it and he's going to talk about the mechanism of that the the ionic mechanism of that particular difference in synapses i'm going to show you a little bit about the structure of the two so this is the characteristic of an excitatory nerve ending where this is an excitatory synapse as we call it so the characteristics are that we have round vesicles here that are a lot of these are located throughout the nerve ending and a lot of times they're attached to microfilaments keeps them in place the ones that are important for the actual synaptic transmission are the ones that are down here close to this dark stuff that i have drawn in here because they're going to have to fuse with that membrane just as soon as the stimulus reaches the nerve ending so they really rapidly release their neurotransmitter and these are drawn as round vesicles containing the neurotransmitter so that's the most important aspect of the nerve ending or those vesicles remember those came down from the soma so we have a lot of mitochondria in the nerve endings because there's a lot of energy necessary for the pumps that are working down here and dr bernal talked about those pumps we also have uh these microfilaments which are necessary for the movement it's believed and the tethering of the vesicles that are not right next to the release site we can have smooth endoplasmic reticulum that's within this nerve ending have you in other courses learned why smooth endoplasmic reticulum is so important anybody tell me what that is calcium storage and a lot of calcium comes in from the outside in the mechanism of releasing the neurotransmitter but a lot of calcium is released from the endoplasmic reticulum as well and the endopla this endoplasmic reticulum is necessary to take that calcium up rapidly so that you can have a very discreet release process so mitochondria synaptic vesicles smooth in the plasma reticulum uh the dense material is the area where the release actually occurs there are proteins there that we'll talk about on next wednesday that are involved in that release process uh on the post-synaptic side though this that's a that's another thing that i've introduced a word that i should define this is presynaptic and this cell is postsynaptic that's the way we talk about it dr byrne may have talked to you about that but he'll really go into it in detail in his lecture today and in subsequent lectures so in the post-synaptic cell we can have the dense material also here it's really not illustrated it is in the next slide so recall that's where the receptors that dr bean talk to you about are tethered so that they're uh in the location that's necessary in order to receive the neurotransmitter and propagate the stimulus okay we also have here a slide showing and this is not in the syllabus for some reason i took it out i can't remember why the uh the this is exactly the same as with a excitatory synapse the difference is the process of preparing for electron microscopy causes the these vesicles to flatten and so a scientist who is studying various areas of the brain to understand the mechanisms of whether it's inhibitory excitatory can tell whether it's inhibitory if the vesicles are flattened otherwise it's identical we have dense material we have the smooth endoplasmic reticulum mitochondria microfilaments and

### Segment 6 (25:00 - 30:00) [25:00]

the release of the transmitter at this site is going to inhibit the cell this is a nice slide i like to show just to illustrate the large number of synapses on this particular motor neuron cell and you can see these are synapses that are on the cell soma we really can't tell where the dendrites are here but this is illustrative and these black dots are the synapses that are on the and this is only one section a light mic a light microscopic section through this so this is obviously a three-dimensional structure so they're going to be all over this particular neuron this shows the difference between the excitatory and inhibitory when we do electron microscopy but it also is really nice to illustrate the large number of vesicles that you find in a nerve terminal the mitochondria that are uh prominent shows a little bit about the structure these uh process these uh their terminals okay that's all for the cell biology the structure and function that is just to expand on what dr byrne talked about what i've shown here is the cell that we talked about was this multipolar cell this model cell with the soma and the dendrites and the axon and the terminals that's fairly common structure characteristic of neurons but we have others many others so for example we have what's called a unipolar cell so the cell bodies down here the axons here and the dendrites are here whenever we talk about any one of these where the dendrites are is a functional thing the the nerve endings that are going to be stimulated the cell are up here and so this is this red dot illustrates where the action potential is going to be generated here is a bipolar cell again here's where the action potential is going to be generated this is axon cell body axon so this is for instance found in the olfactory system and in the retina bipolar cells in the here's uh one that's fairly common that is a pseudo-unipolar cell we call it that because it cell body is off to the side and here we have down here the uh where stimulus is occurring and this is common to sensory neurons so we have pain fibers down here we may have temperature fibers uh different kinds of sensory uh modalities the ac the axon is the uh the action potential the spikes generated here it goes up and leads to the central axons that are in the spinal cord so these are different kinds of variations that of shaped that we talk about that's different than this one that we use to illustrate the uh and dr byrne is going to continue to use this particular structure as the example so this just shows the direction that impulse is moving in each one of these cases how else can we name neurons other than all of this uh was based on shape unipolar the number of processes basically multi uh multiple processes by two processes one process and then this pseudo uniprolate well there are other ways and that is uh the early scientists that i mentioned like uh kahal and golgi they based it on and they're the ones as it turns out that discovered that heavy metals will stain specific neurons and so they named on shape others and some of them are named for the guy who discovered it so we have that process but the one that's really the most important is this one and that is the neurotransmitter that the cell utilizes and we'll be talking about that um in more in the lectures later uh in this blog so for example a pyramidal cell it's shaped like a pyramid down here this isn't a very good pyramid but it's it's the and it's the pyramidal cells that are in the

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cerebral cortex you have five layers of these cells so that's one way we have granule cells they're just little itty bitty spots so when we talk about the cerebellum they're going to have granule cells uh they're stellate cells and so forth so that's one of the other ways we talk about this all based on the ability to look at the specific structure using these heavy metals here's based on the scientist this is an example of a purkinje cell her kenji discovered this in the cerebellum this is the actual stained cell here we actually have three of them uh together here this is very and this kind of shape is important because for this kind of cell is important because this particular cell looks like it might have a huge number of dendrites radiating from the cell body the reality is that the prekenji cell if you look if you turn this direction there would be one process because all of these are in a single pane so it's like i'm standing like this and i turn like this looks like this is the plane of the purkinje cell and that's because that the shape of that cell dictates and is responsible for the very unique characteristics it has in the cerebellar physiology and we'll talk about that later in the course when we talk about movement control in the cerebellum but golgi and purkinje are examples of scientists who named these kinds of cells and this is a purkinje cell so then the last of this particular theme is the neurotransmitter that the cell contains so acetylcholine cells norepinephrine secreting cells dopamine serotonin gaba neuropeptide secreting cells glutamate secreting cells all of these are existent in specific organization of the brain so how do we know where they are well there are two approaches one is you can make an antibody that will specifically recognize acetylcholine then you use that antibody to stain slices of the brain and you can then reconstruct the cholinergic system of the brain the same is true for norepinephrine dopamine serotonin gaba neuropeptides these are all important neurotransmitters that you've heard of and we're going to talk a lot but we now know a lot about where they are because we can use this approach of either making antibodies to the these uh transmitters themselves but there's another way we can go about it and it turned out to be even more effective and that is some of these cells contain enzymes that are only in cells that make the neurotransmitter so you can make an antibody to those enzymes and then map where those cells are so we have a adrenergic system a norepinephrine system we have serotonin system and so forth and we'll talk about that in the course where that becomes important for behavior especially so what to know about what i've just told you um just basic structure i don't expect you to know what the components of uh neurofilaments are anything like that just know that neurofilaments are important where the organelles are and what generally what their function is how we name neurons there's these different ways okay glia cells glial cells are the predominant cell in the cns there are uh 80 to 90 of all the cells in the cns or glass cells this usually surprises people it surprised me when i first learned it they are the basic shape of the cns is made up of glial cells the nerve cells are superimposed on that so the glia cells are the supportive uh physically supportive makeup of the cns but even as important they're all

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a supportive cell because they maintain the ionic environment that all of this nerve function that you're going to learn about in the next week or so takes place without those gly cells to maintain that ionic milieu none of it could happen so they're really important they're classified based on size and on shape so size that we have macroglia which there are four different and we have microglia one cell how what's the difference between glia cells and neurons uh they are less electrically excitable they are but not their primary function they can be depolarized they do have a membrane potential but that's not their function that's why i say less electrically excitable they don't form synapses at all they only have one process type they don't have dendrites and axons they can retain their capacity to divide and in fact they divide upon receiving the proper stimulus pretty readily so you can have glial cells dividing uh in response to some kind of an injury for example nerve cells don't divide as a general rule the reality is they do divide but it's so rare that they divide that we talk about them not dividing and it's only in certain regions that they appear to divide there we geosize are identified with their size their shape and the type of process but i add this because if you become a or you talk to a neuropathologist they talk about glia cells based on what the nucleus looks like because that's what they see when they slice the brain and stain it and the different glia cells have different nuclear morphologies in the syllabus i go into more detail on this don't worry about that detail it's not really important at this stage like this chromatin density and so forth don't worry about that just know that that's another way of classifying uh glial cells so the macroglia are astrocytes they look like stars they're oligodendroglia oligo means few these just have a few processes there are ependymal cells uh in lab yesterday i don't know where no way you wouldn't have seen the ependyma but it's uh these are the cells that line the ventricles you saw the ventricles presumably but you wouldn't see the epinephrine and schwann cells which are comparable to the lingua dendrocytes which i'll get into in a second are the source of uh axon myelin in the periphery so astrocytes we have two kinds of protoplasmic and fibrous these guys are prominent in the gray matter and these white matter fibers are in the white they have different shapes this is a drawing that i made of a protoplasmic astrocyte that is kind of has thicker processes we call it murky kind of looking processes and it uh is different than the fibrous which has these thin processes the protoplasmic astrocyte actually forms sheets around neurons the fibrous astrocytes makes contacts with these long extensions onto blood vessels and onto some neurons and onto the glute next the glio-limatans that lines the outer boundary of the cns and as i said these prominate and predominate in the white this just shows you this difference it is kind of a envelope type process that comes out and this is this very spiky fibrous process physical structure barrier between neurons metabolically they maintain the ionic environment the ph is maintained by them and when we talk about certain neurotransmitters they all actually remove the neurotransmitters from the extracellular space uh very important function for amino acid

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transmitters that dr waxen will talk to you about in about two weeks they uh dr bean talked to you about how they would can guide axons during development and finally this is one of their more important functions is that they migrate and proliferate if there's injury and they'll form what's called a glial scar in the and you'll see some of the brains that you guys look at later on when you look at the slices you may find glial straws uh the next one we're going to talk about is the oligodendroglia few processes not nearly as many as the astrocytes these form the myelin in the cns and they also insulate the soma of neurons uh and then they're called satellite cells this shows you the dense staining oligodendroglia coming out here and wrapping around an axon to form the myelin sheath they have a very characteristic that all the cells that do this aren't associated directly with the axon they're out here in the periphery away from the axon and they send processes out which wrap around the axon and so you'll have a number of different oligodendroglia which will form the um the myelin sheath in for a particular axon so here's one here's one and so there'll be a number of oligar gender glitter that do that this shows the process of their doing i show that specifically because the schwann cell which forms the um myelin sheath for peripheral neurons this is all the oligar all cns neurons forms it uh in a different manner it forms it uh it forms the same kind of a insulating membrane around the uh the myelin around the axon you can see here that we have a schwann cell that now is directly adjacent to this axon and it has formed the myelin sheath the way it does that it squeezes its plasma its cytoplasm out as it wraps around and that's shown this kind of a way where it wraps around and so each one of these particular areas of insulation is formed by a single schwann cell so that's the difference between the schwann cells and the oligodendrogram the macroglia that are lining the uh that the ventricles and the spinal cord canal are these ependymal cells they are composed of either columnar or more flattened cells which can propel the cerebral spinal fluid down there down the ventricle there is both the uh release of substances and the uptake of subs substances through these dependable cells in certain areas it's more prominent than others but it's an important mechanism when these are uh situated on a basal laminar membrane and there's blood vessels associated with that then this is called the choroid plexus and whether you saw a choroid plexus yesterday when you looked at the brains and the chloride plexus is responsible for the formation of the cerebral spinal fluid there's tufts of these in the ventricles and when you look at your brains in the course you can pick out these little tufts of choroid plexus this just shows them in electron micrographic and that's the choroid plexus last we have the microglia these are really small cells all the ones that i've talked about so far derived from ectodermal region these are derived from a mesoderm and they're so small that you can't find them for the most part they multiply in response to injury

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similar to what the astrocytes do uh and like the astrocytes they phagocytize material and so if you have a an injury in the brain you if you slice that brain later on and try to understand what's going on you may well find lots of microglial nuclei that are there it's hard to find the neck microglia themselves so what to know about glial uh that there are more of those than neurons they're supportive in the ways that i've talked about uh they're important in a lot of different ways maintenance development uh if we didn't have them obviously we wouldn't have neural functions they facilitate axon regeneration we'll talk about that later in the course taliyah are the major source of cancer in the brain it's probably the one of the most important uh to know about okay thank you very much for your attention you