 Hey everybody, Dr. O here. So we've covered the neurons, now we're going to cover the other half of your neuro tissue or your nervous system, which is the neuroglia. So glia means glue, so this word actually means nerve glue. These neuroglial cells will cover six types, four in the central nervous system and two in the peripheral nervous system. They make up about half the volume of your nervous system, so they're very, very important. They don't send and receive electrical impulses like neurons do, but they support the neurons and protect them so they can do their job. So we're going to start with the central nervous system. There are four types here. We see appendable cells, astrocytes, microglial cells and oligodendrocytes. Let's go ahead and go through them. So let's start with appendable cells. When you hear appendable cells, think cerebrospinal fluid. You'll see that the four ventricles in the brain and the central canal that runs down the center of the spinal cord are going to be full of cerebrospinal fluid. They're also going to be lined with these special appendable cells that form an epithelium, which is called the appendoma. So appendable cells make the appendoma. Everything associated with cerebrospinal fluid is caused by these appendable cells. Some of them secrete cerebrospinal fluid. Some circulate it. Some monitor it. It monitor its composition. Others have stem cells that can repair it. So anything associated with cerebrospinal fluid, think appendable cells. You'll see here in the middle this coroid plexus. That's going to be the combination of vascular supply and appendable cells that play a major role in production of cerebrospinal fluid. But you'll find these appendable cells everywhere that you find cerebrospinal fluid. So that's the appendable cells. Next we have the astrocytes. I mean, these are critically important key players. They do lots of different functions. But the two key ones that I want you to know, number one, they maintain what's called the blood-brain barrier. There are physical things that protect your brain, like your skull and your cerebrospinal fluid is going to cushion your brain and these types of things. But the blood-brain barrier is a biochemical barrier that tries to keep your brain and even the spinal cord tries to keep them sterile. It tries to keep things out. So the blood-brain barrier, if it's fully intact, there are lots of things that cannot enter the brain in ways to get under other parts of your body. This can be really good or really bad. This means it's way less likely to get pathogens or get infections in your brain, but it also means if you have those infections, then your immune cells can't get to the side of infection either. So the blood-brain barrier is very important. The astrocytes are what maintain the blood-brain barrier. The other key feature of astrocytes is they create the scaffolding. They create the three-dimensional framework that builds your central nervous system. They play a role in repairing damage to neural tissue. They guide neuron development when new nerves are developing and they also control the environment of the central nervous system. So as you can see, lots of important functions, but the blood-brain barrier and creating the three-dimensional framework that your CNS is built on are the two key functions that I want you to know. So those are your astrocytes. Next, we have the oligodendrocytes. So these are these small little cells, but they have these huge processes that can come off of them. So they don't look anything like the other cells, but their function is super, super important. The main thing they do is they myelinate the nerves of your central nervous system. So myelin is a fatty insulation that decreases resistance. So a myelinated nerve can send a signal much faster than an unmyelinated nerve. I hate saying that. So we have different types of nerves, basically the size of a nerve and whether or not it's covered in myelin will determine how quickly it can send and receive electrical impulses. So oligodendrocytes, just remember they myelinate the nerves of your central nervous system. So why is myelin so important? Let me just give you a couple of examples. When a baby's born, they have all their nerves. The reason they can't control their bodies, can't control their arms, and then later can't control their legs, is because the nerves need to be myelinated as they develop. Another good example would be, and this is also why it's very important to make sure kids get enough fat in their diet. You need adequate fat to build the brain and to build these myelin sheaths. The other example would be MS. MS is a multiple sclerosis is an autoimmune disease that affects the myelin sheath. The underlying nerves are fine. I'm sure they're taking some damage from inflammation, but think about all the symptoms and all the problems that can be caused by multiple sclerosis. It's because those nerves are losing their myelin sheath. So whether you're a baby or an adult, myelin is super important. The oligodendrocytes are the cells that myelinate the nerves of your central nervous system. We do have some nerves that aren't myelinated, they're unmyelinated, and they're going to send signals much, much more slowly. A couple meters a second versus over a hundred potentially. All right, that's the oligodendrocytes. The last neuroglia or nerve glue cell or glial cell of the central nervous system is the microglia, which you see up there in the corner. These are small. They have these little tiny fine branch processes on them. I consider them the immune system of the central nervous system. So because your other immune cells can't get into the central nervous system because of that blood brain barrier, the microglia, they have to play a big role in engulfing debris, recycling things. So they clean up cellular debris, they clean up waste products, and they also can kill and destroy and clean up pathogens. So that's why I call them the immune system of the central nervous system. These seem to be more and more important with new research coming out over the last few years that microglial dysfunction, if these cells become dysfunctional, they can actually start to churn out a lot of inflammatory mediators. They can increase brain inflammation, and this has been linked to dementia, Alzheimer's, all sorts of things. So we don't actually know for sure what causes Alzheimer's, but these new theories of brain inflammation being caused by dysfunctional microglia is something I would definitely pay attention to. All right, so those are the four types of neuroglial cells in the central nervous system, the ependymal cells, astrocytes, oligodendrocytes, and microglia. Now let's go to the peripheral nervous system. So here you see, anywhere you see cell bodies of nerves in the peripheral nervous system clustered together, it's called a ganglion. So here at this ganglion, we see the two types of neuroglia that are in the peripheral nervous system. Let's talk about satellite cells first. Pretty simple. They surround these ganglion and satellite cells, they regulate the environment around the neuron. So they create an environment where the neuron can function. They make sure that the neurons are getting the, have the right pH, make sure they gain the nutrients they need, removing waste products, these types of things. So satellite cells, just remember, they regulate the environment that these peripheral nerves are in, similar to the function of the astrocyte in the central nervous system. And the last neuroglial cell is called the Schwann cells, or neurolemicytes. I'll put that on the screen for you, the other name. They myelinate the peripheral, the nerves in the peripheral nervous system. So just like the oligodendrocytes are going to myelinate the nerves, neurons in your central nervous system, Schwann cells will myelinate the nerves of the peripheral nervous system. Okay, so those are your six neuroglial cells, the four of the central nervous system and the two of the peripheral nervous system, very important that you know these. So watch this again, take some notes, do whatever you need to do. I hope this helps, have a wonderful day, be blessed.