Cells of the Nervous System (Neurons and Glia)

now we know that the nervous system has a number of different cell types associated with it and these cell types can be broken up into two categories first is neurons second is glia so we're going to have a look at the different types of neurons and glia within the nervous system but first we need to divide the nervous system into the central and peripheral remember the central nervous system is the brain brainstem and spinal cord and the peripheral nervous system all the nerves that come out and away and back in to the brain brainstem and spinal cord so what we're going to do is have a look at neurons and glia separated by these two classifications central nervous system and peripheral nervous system now the one cell type that is nearly indistinguishable from the two the neurons so neurons will be found everywhere in this within the central nervous system so even just the brain for example there's going to be a hundred billion neurons within the spinal cord there's going to be about 100 to 200 million neurons even in the gut there's actually about half a billion neurons as well so neurons are all over the place what does a general neuron look like because they all look very different so I'm just going to draw up probably a picture of a neuron that you've seen before and highlight some of the important structural components all right so first thing is neurons we need to talk about very quickly what is in your honor what does it do well very simply neurons are the excitable cells so what does that mean to be an excitable cell well there's some cells within the body that can be excited through certain electrical impulses these cells are generally neurons and muscular or muscle cells or myocytes and what these cells do is when they're excited they can perform some sort of activity or function when it comes to neurons they're excitable cells and when they're excited what they do is they send signals and communicate sends signals communicate the question is what do they communicate with well a couple of things neurons can either communicate with other neurons neurons can communicate with muscles when yours can communicate with glands okay so they're the excitable cells that can communicate to other neurons muscles and glands what do they look like well you know that I'm probably one of the best drawers you've ever seen so I'm gonna try my hardest to maintain my notoriety has been a wonderful drawer alright not the best but that's okay okay so this is probably a or similar to a picture that you may have seen in your textbook for example this is a neuron a couple of things we need to identify then you're on first thing is this these projections you see at the end here these are called dendrites and what dendrites do is they receive any incoming signals so dendrites will receive a signal maybe coming from another neuron or some sort of receptor coming in and then you've got the major or largest portion of the cell here called the soma and the soma is the cell body remember so mum means body and you're also going to have a nucleus within that soma you're also going to have all the other types of organelles that you've heard of before such as the Golgi apparatus endoplasmic reticulum ribosomes mitochondria and so forth they're all located within this soma then you can have a part of the neuron which is basically the neck between the soma and the axon called the axon hillock axon hillock now the axon hillock is important because this is the area that starts to propagate and produce the action potential which is the signal that's going to be sent down this axon which means that this is the axon the axon is the longest projection coming off of a neuron and at the end of an axon where the neuron terminates they're called the terminal receptor they're called the synaptic terminals synaptic terminals or synaptic bulbs it's up to you this is where the signal finishes and then either needs to communicate with another neuron or communicate with the muscle or communicate with a gland remember neurons don't actually touch other neurons neurons don't touch muscles or glands there is a little gap here called the synapse which is where chemical signals need to diffuse across in order to tell the next either neuron muscle or gland what to do they can be excitatory or inhibitory so this is the general outline of a neuron now remember most neurons we'll be myelinated which means they have an insulation or a rubber coating protecting certain parts of the axon now I said rubber coating it's obviously not rubber but it's synonymous with the rubber coating that you have lining the outside of your wires at home why do we have this rubber coating well it protects the signal that's being sent through and allows that signal to continue so if that rubber coating was stripped what may happen is that you may lose the signal on the other end or the quality may be diminished that's the same thing that happens here we need this myelin which is basically just fatty layers okay that's just fat that's wrapped around this myelin to insulate the signal that's being sent down the axon help it propagate down without being lost okay now that's a neuron let's now talk about the other cell types within the nervous system which are called glia so firstly I want to look at glia with an essential nervous system glia in central nervous system first thing is what does glia mean glia is Greek for glue and what they are if we have a look at the function is basically the supporting cells of the nervous system so their supporting cells and what that means is they help maintain the internal environment and that environment around the neuron so there's many different types of glia all having many different roles but overall their role is to support the neurons in one way or another so let's have a look at the different types first type I want to talk about are the types of glia that help wrap the axons of the neuron within the central nervous system this type of glia are called oligodendrocytes all we got NGO sites what are they function they Milan eight neurons within the central nervous system so that's brain brainstem and spinal cord so they Milan eight CNS neurons how do they do it well this is important because fold adjust draw a very dodgy picture of neurons and another neuron here okay what the oligodendrocytes do is this will be an oligodendrocyte they have these projections these arms that come off and they start to wrap around the axons of the neurons like that so this is what the oligodendrocyte is doing the central nervous system to protect the axons of neurons what's another type of glia within the central nervous system well another topically are astrocytes astros sounds like space right Astro well this is important because Astro referring to star these astrocytes look like stars so they basically look like this and again very rough drawing you can see that the soma have all these arms projecting off it like that so it looks like a star what astrocytes do well they play a couple of different roles one of which is to maintain the environment surrounding the neurons but another important role is that it is involved in the blood-brain barrier which means it helps regulate what doesn't does not go from the blood stream in the systemic circulation into the blood stream that's supplying the brain very important what's another type of glia ependymal cells remember these are all glia of the central nervous system ependymal cells well in your brain i've done a video on this so you should know about it in the brain there are hollowed-out cavities these cavities are called ventricles and these ventricles produce cerebral spinal fluid which floats around the brain floats around the brain stem floats around the spinal cord helps to wash away any metabolic byproducts deliver nutrients and also provide a cushioning if the brain and spinal cord starts to move around the ventricles produce this CSF in these ventricles so I'm gonna try and draw so there's a brain you'll find that there's four ventricles within the brain you're gonna have two lateral ventricles one in each hemisphere you're going to have fourth ventricle third ventricle sorry and a fourth ventricle okay these ventricles here on the roof and lining other aspects of the ventricles but predominately the rooves you're gonna have these cell types called ependymal cells and what these ependymal cells do is that they produce the CSF so ependymal cells produce the cerebral spinal fluid within the ventricles what's the last cell type i want to talk about when it comes to glir in the central nervous system well it's going to be a cell type called microglia Micro means small they're small glia they are small glia and they look like immune cells so they've got these projections that come off and what they do is they phagocytose they engulf anything that should not be there so they play an immune ER --all and phagocytose so immune eran all right so the glir within the central nervous system oligodendrocytes Mullenix and the neurons astrocytes protect the neurons by forming part of the blood-brain barrier ependymal cells produced the cerebral spinal fluid in the ventricles and microglia playing immune role because they phagocytose any invading particles or substances that shouldn't be there what about the glia within the peripheral nervous system well there's only two I want to talk about first type are the Schwann cells okay what Ashwin cells well I told you that oligodendrocytes create the myelin in the central nervous system Schwann cells create the myelin in the peripheral nervous system so they're the myelinating cells within the peripheral nervous system but they do it in a different way to oligodendrocytes that's why I showed you that image there with the oligodendrocytes projecting out and wrapping around Schwann cells do it differently if I were to draw up again two neurons very dodgy Schwann cells each so here you can see one oligodendrocytes creates multiple myelinated regions one Schwann cell creates one myelinated region and then another Sean cell and then another Schwann cell and then another Sean cell okay the last type of cell I want to talk about of glia within the peripheral nervous system our satellite cells okay what our satellite cells do what they myelin out as well they myelin ate the cell bodies of neurons within the peripheral nervous system now generally speaking not all neurons look like this we've got the cell body on one end in the axon on the other end sometimes you'll find neurons look like this well the cell body sits halfway through okay this is often what you're going to find with sensory neurons for example and what satellite cells do is they tend to myelinate and protect the cell body in the peripheral nervous system okay so they regulate that environment help protect them maintain the soma or the body of the neuron in the peripheral nervous system another interesting point that you should know is this cell bodies of neurons in the central nervous system are called cell bodies cell bodies in the peripheral nervous system are turned ganglia ganglia is cell body in the peripheral nervous system okay that's a quick summary of neurons and glia within the nervous system

Channel: Dr Matt & Dr Mike

Views: 52,102

Rating: 4.9490447 out of 5

Keywords: oligodendricytes, ependymal cells, astrocytes, microglia, schwann cells, satellite cells, neuron, neurons, cells, nervous system

Id: yT9Ad01oUgc

Length: 13min 35sec (815 seconds)

Published: Mon Apr 16 2018