Hello, I'm Jennifer Carbrey, I'm a faculty member in the cell biology department at Duke, and I'm going to give you several lectures about the nervous system. We're going to start off talking about some of the cell types and one of the main cell types that I'm sure you're familiar with are neurons. And that's actually what's shown in this title slide, where we have a microscopic image of a neuron cell body that's darkly stained with a light nucleus in the center. So we'll be talking mostly about neurons in this section. We'll also talk a little about glial cells. Then, in future sessions, we're gonna talk about how these cells communicate, how neurons communicate. So keep in mind, you've already heard some about the endocrine system from Dr. Jacoy where it's responding to stimuli in a slow manner. And based on the stimuli that it's responding to that's perfectly fine. That works just well. However with the nervous system, a lot of what it's going to be responding to needs to be responded to very quickly. So if you put your hand on a hot stove, you need to remove it quickly and you also need to sense the heat quickly. If something's flying at you, you need to be able to see it and duck quickly. And so, a lot of what we're gonna be talking about is how this can be accomplished, the speed and very specificity of the nervous system and how that can be achieved. And then at the end we'll put together how these neurons come together and are organized to get these tasks done. So we're gonna start off talking about neurons, and neurons have different parts to them. They can have very different morphologies, but a typical one is they're gonna have a cell body, which is kind of the main portion of the neuron that's gonna contain the nucleus and a lot of the organelles. And then coming off of that cell body are going to be cell processes called dendrites, that are going to receive information and there can be thousands of them on neurons. So there can be many, many dendrites that are all receiving information and we'll learn more about how that happens. And then often a neuron is going to have a single axon, which you can remember since axon starts with an A, it is usually taking information away from the cell body of the neuron. So often it has a single axon that's taking information away from the cell body and where the axon meets the cell body is called the initial segment of the axon and in future sessions, we'll talk about the significance of the initial segment of the axon. And then, often, the axon can branch to form different terminals. And we'll be talking about those in future sessions, as well. So, then there's only a few other types of supporting cells, that are called glial cells, that we're gonna talk about. So one type of glial cells are Schwann cells, which are found in the peripheral nervous system. So this is going to be in the parts of the nervous system like nerves and ganglia that are outside of the central nervous system which consists of the brain and the spinal cord. So these Schwann cells are there to support more specifically the axons of neurons. And what they do is they form this extension of specialized membrane and they wrap and wrap and wrap around a specific segment of an axon. So each one of these blue structures is a separate Schwann cell that's wrapping around that portion of the axon and they leave little spaces between themselves and we'll talk about the significance of that in future sessions. So, here's kind of a close-up, where you can see the Schwann cell nucleus and the Schwann cell wrapping and wrapping around the axon, and that's acting to electrically insulate that portion of the axon. So the schwann cells are the cells are the cells that myelinate in the peripheral nervous system, and then in the central nervous system we have oligodendrocytes which are the glial cells that myelinate neurons in the central nervous system. They use a very similar process of wrapping and wrapping around a section of axon. However, these cells are a little different, because oligodendrocytes send out several processes each one myelinating a different segment of an axon or axons. Okay? And that's what's shown in this diagram where we have the oligodendrocyte cell body and it's sending out several processes that each myelinate a different segment of axon. But the idea is the same, to electrically insulate that portion of axon and we'll talk about in future sessions why that's going to be important. So most of the information on this slide we've already talked about. How in the peripheral nervous system we have Schwann cells that myelinate. In the central nervous system that's oligodendrocytes. And then there's just a couple other cell types I wanna mention. One are microglial cells which are immune cells of the central nervous system. And then another really important cell type that we're not gonna talk much about, but it's becoming increasingly clear that they're very important in supporting neurons, and these are astrocytes. They support neurons metabolically, they maintain the extra cellular environment of the neurons, and they're important in processes such as synapse formation, which is when two neurons come together. So even though we're not going to really say any more about them, keep in mind that astrocytes are crucial parts of the central nervous system in order to support neurons. So this is the end of our first video where we talked about neurons and glia cells. Neurons are gonna be the cells that are gonna transmit the information. And we're gonna talk about how that's going to happen in the next few sessions. And then glia cells are going to be what provide support to neurons in multiple different ways.
