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 are 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 bit about glial cells. Then, in future sessions, we're going to talk about how these cells communicate, how neurons communicate. So, keep in mind, you've already heard some about the endocrine system from Dr. Jakoi, 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 going to be talking about is how this can be accomplished. This speed and very sense, specificity of the nervous system and how that can be achieved. And at the end, we'll put together how these neurons come together and are organized to get these tasks done. So we're going to start off talking about neurons and neurons have different parts to them. They have, they can have very different morphologies, but a typical one is that they're going to have a cell body, which is kind of the, the main portion of the neuron that's going to contain the nucleus and and a lot of the organelles. And then coming off of that cell body are going to be 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 going to 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 that, 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, 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 a 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 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 have, 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 mylenating 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 sections why that is 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 want to 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 going to talk much about, but it's, it's becoming increasingly clear that they are very important in supporting neurons and these are astrocytes. They support neurons metabolically, they maintain the extracellular environment of the neurons, and they're important in processes such as synapse formations, which is when two neurons come together. So, even though we're not going to really say anymore 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 glial cells. Neurons are going to be what are, going to, the cells that are going to transmit information. And we're going to talk about how that's going to happen in the next few sessions. And then glial cells are going to be what provides support to neurons in multiple different ways.
