[Music] hey everyone welcome to professor long selectors in anatomy and physiology quick disclaimer these videos are being shot very quickly very crudely in a very impromptu fashion with no editing because we're the coronavirus shut down I've been saying this with every video and my students are tired of it but these videos may end up on YouTube for a while and anyone tuning in later I don't want them to think this is the best that I can do I just don't have time to edit you learn the software and doing the editing so all of these videos are being shot from home because all of our online times all of our face-to-face classes have been switched to online and the time frame is tight with all the other things that we have to do I'm learning how to do testing software and a number of other things and I'm dealing with students emails and questions about exams and other things so time is limited so these are quick they're impromptu they're one takes if you hear a dog bark in the background or a kid say hey Dad what's up that's because I'm shooting them at home bear with me okay we're gonna really use these warts and all now we left off in the nervous system on the bottom of page 70 we were talking about synaptic activity in the last video and I have a worksheet up for my students and there's a lot of information on page 70 you guys need to understand how synapses work and once you understand one synapse you understand them all just the name of the neurotransmitter changes the name of the enzyme and the name of the receptor and then you need to know which ones are excitatory inhibitory we went over a very small sampling of neurotransmitters and synapses but you can fill in the details later on now at the bottom of page 70 we're talking about the glial cells or what some people call neuroglia and sometimes the words pronounced neuroglia you know tomato tomahto so neuroglia also are abbreviated as glia glial cells are like the glue that holds the nervous system together they do support for neurons remember the nervous system is made up of two major classes of cells neurons and neural glia we've been talking about neuron now glia are somewhat like I said the glue that holds nervous system together they support the neurons in their functioning physically biochemically nutritionally emotionally not not emotionally just kidding there's emotional support Leah no but they do is a lot of biochemical nutritional and physical support we're going to focus on six major glial cells and really five but that I'm gonna mention one of them so in the central nervous system in our brain and spinal cord we have four types of glial cells that are found there one type of glial cell is called an astrocyte astrocytes get the idea or get their name from the fact that they are star-shaped okay astrocytes do a lot of sort of physical support they make up the framework that holds all the axons and the dendrites almost like telephone poles supporting wires similar to that concept one of the things that a number of astrocytes can do is this we've talked to before I believe we talked well we have it there's a part of your brain called the choroid plexus the choroid plexus is a network of capillaries very small blood vessels the lamp that allow things to exit the blood stream to nourish our neurons and things to come in to the bloodstream like the neuronal wastes and all of this other stuff so we have to feed our neurons we have to feed them all the nutrients all the sugars and fats and proteins and amino acids and water and beneficial ions flows out of our bloodstream and in between the cells it forms the interstitial fluid of the brain those cells will consume all the nutrients make waste and dump their waste into the surrounding interstitial fluid well if we don't wash it away the waste would build up and poison our neurons they would become septic in their own fluids so one of the things we have to do is get stuff out of the bloodstream to feed ourselves and then from the cells back into the bloodstream so we can wash it away and clean it this is how our nervous system and our circulatory system we're going to kind of is that the structure called the choroid plexus so we have these specialized blood vessels that have a severity thin-wall single squamous cell thick their capillaries and all the nutrients and the good stuff will flow out of here ions glucose lipids amino acids our neurons will take in all that nutrients to make energy to rebuild to make proteins to heal and they'll dump carbon dioxide oh by the way oxygen they need oxygen for energy they'll dump carbon dioxide and waste into this fluid and it has to be reabsorbed into the bloodstream now we talked early in part one about this concept called homeostasis one of the central tenets of this course and we talked about a range of conditions for homeostatic conditions for example we talked about temperature there's a range of temperatures at which our cells chemistry can function that temperature can go up and down a little bit 98.6 is the optimal temperature in Fahrenheit and if it goes up a little bit to 99 we're okay if it goes down a little bit you know ninety eight point eight we're okay we can take small fluctuations so there's a homeostatic range if it gets too hot or too cold that shuts down the chemistry of ourselves and they die that would be pathology we also look at things like salt concentrations too much sodium and potassium can shut down neurons a neuron functioning because they used sodium and potassium and calcium and chloride so ion concentration has a range here we can look at oxygen concentrations we can look at glucose concentrations there's a range okay now some cells have a very wide range they're very tough and Hardy cells like skin cells and other cells you can mess with their conditions and they're okay some cells have very narrow ranges of homeostatic conditions everything must be precisely perfect or they start falling apart they can't hang I think of them as big whips or weenies in the nervous system the biggest wimps and weenies are neurons you mess with their oxygen concentration their sodium and potassium and glucose and lipid concentrations and they don't function very well at all now not only that but if you think about the blood stream let's look at one blood vessel look at it like a river and as water is flowing through this river if I have people living down here these would represent ourselves like neurons and other cells in the human body eventually this whole river circulates back around and we have some filter organs like the kidneys and our liver which are going to clean that blood but there are some cells that are dumping waste into there to the stream that other cells could be exposed to now some cells are pretty Hardy they can take a little bit of it but neurons can't so neurons have to take this fluid run it through a filtration membrane filter it off and then dump their waste back in okay that fluid that gets filtered out of our blood is called cerebrospinal fluid CSF and the special blood vessels are called the choroid plexus means a network so the choroid plexus is a special series of blood vessels that filter our blood pull out the cerebrospinal fluid and leave all the rest in the bloodstream and then the CSF will bathe our neurons and nutrients and ions and goodness and then they dump their waste back into the blood stream so there's a reason I mentioned the choroid plexus give me a second my dog is part [Music] all right I apologize but again I'm doing these at home and I'm not wasting seven minutes of a video and starting over else I'd never get done so now when I look at these blood vessels of the choroid plexus it would be like this little capillary what helps form part of that filtration memory now we filter cerebral spinal fluid out of our blood happens at these capillaries so inside here would be our plasma and out here would be cerebral spinal fluid well it turns out that astrocytes are these little star shaped cells and then of these long extensions or I should say short extensions and they end up in these little feet like structures that sit up against a capillary and they can make several of these sometimes not only on one capillary but on others and other astrocytes will form these little feet like structures and as we put them together from a number of astrocytes they create this little filtration membranes that membrane that allows us to keep large molecules from getting out into the cerebrospinal fluid some trash and toxins and other things but only let little tiny molecules through into and out they call that the blood-brain barrier so we say that astrocytes help form the blood-brain barrier for CSF formation again CS f stands for cerebrospinal fluid it's written in the note set so you can look at okay so astrocytes do some physical support of neurons but they're also helping form the blood-brain barrier for the filtration of CSF now a second type of glial cell that we can talk about it is called an ependymal cell and some people say ependymal cells okay tomato tomahto again ependymal cells can monitor CSF and they make adjustments to it they have the ability and they're found in certain parts of the ventricular system but of these ependymal cells can they sort of line the third ventricle and some of the other chambers the ventricular system and the central canal of the spinal cord and it's like they constantly sample the cerebrospinal fluid and can make adjustments to the concentrations of certain things that's a real generalized overview but that's good enough for us for now the third type of glial cell that's in the CNS that we can talk about is called microglia the microglia are modified immune cells or white blood cells we usually abbreviate white blood cells as WBC's and what they do is just like any immune cell anything that does sneak out through the blood-brain barrier into the brain that doesn't belong they can gobble it up they are phagocytic and they cruise around the brain looking for trash and debris things that don't belong and they literally consume it break it down and digest it they can also help digest old worn-out dying neurons as we lose neurons these guys can help digest them just like any white blood cell can attack and digest any other so so the last of the four glial cells that we can talk about is going to be the oligodendrocytes I usually do these third but I wanted to do them fourth because it's gonna lead us into another one so let me erase some of this simply because I'm running out of room on the board pardon me I dropped my eraser and it's harder to write at the bottom so now you know the function of astrocytes they help form the blood-brain barrier for the formation of CSF and they do some physical support of neurons ependymal cells do some biochemical or nutritional support by adjusting seen SF and microglia protect the neurons by cruising around and acting like immune cells now the last of the four CNS glial cells that we can talk about are called oligodendrocytes now before I talk about that let me mention in the peripheral nervous system in the pianist we have two major glial cells that we're gonna talk about one of them is called Schwann cells well you've already heard about Schwann cells they myelinate axons in the peripheral nervous system so if I have a neuron soma here that's going to taper down at the axon hillock and then the axon goes and branches into two node indriya and we have a synapse down here these cells actually wrap around and cover parts of the axon with a fatty substance called myelin they make up the myelin sheath I talked about this before when we talked about action potential velocity and saltatory conduction these would be showing cells they're filled with the fatty substance called myelin that insulates the neuron and so the action potential as it travels here when jumped to this node of ranvier jumped to this node of ranvier and they assist action potential velocity now there's a couple of other minor things that scientists have discovered that they can help with but ultimately Schwann cells myelinated axons in the peripheral nervous system to aid in action potential velocity well in the CNS we have myelination but there are no strong cells found in the central nervous system it's a look at dinner sites they myelinated axons in the CNS and therefore they aid action potential conduction in the central nervous system and one of the major differences is in the CNS if I were to look at let's say I have an axon here traveling blue the board towards you and I have several axons like this one elimi dentro site I'll put a little D for his name can actually wrap a myelin sheath or rapid membrane around several or a few hence the term illegal axons so and the pns ashwin so myelin it's a single axon and the CNS this oligodendrocytes can myelin a a few hence the term elude oh they have a few branches and the myelinated axons in the CNS damage to this to the myelin sheath would affect how action potentials travel here and that's one of the things that happens in multiple sclerosis is that in ms a lot of the neurons will lose their myelin the Schwann cells seem to unwrap so to speak it messes up for a while and then they'll rewrap and then they'll unwrap and rewrap and over that period of time every time it's kind of like if you tried to unwrap a Christmas present to look at it and then you go back and you try to rewrap it you're never gonna make the wrapping look like it did originally and every time you do it it gets worse and worse over time it gets progressively worse it's one of those episodic diseases that happens in short episodes are sometimes long episodes but happens in an episode and then it disappears for a while and then you have another episode it disappears another episode so it's an episodic disorder but each episode gets a little worse than the previous one and it's tough I have some friends that deal with it anyway so you can understand how myelination affects neurons in the CNS so now the last of the neurons are the neuroglia that we're going to talk about are called satellite cells satellite cells I tended the them as similar to ependymal cells and that they do some nutritional or biochemical support and adjustment for the cells and the peripheral nervous system okay all right so that should cover the glial cells that we've talked about I'm going to stop here and we're gonna be the very last video in the section of the nervous system so I hope you learned something I hope this was helpful and I hope to see you on the flip side so thanks for watching [Music] [Music]