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. One of the main cell types that I'm sure you're familiar with are neurons. That's actually what's shown in this title slide, where we have a microscopic image of a neuron. The cell body is darkly stained with a light nucleus in the center. 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 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. Jacoi where it responds to stimuli in a slow manner. 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 respondd to needs to be responded to very quickly. If you put your hand on a hot stove, you need to remove it quickly. 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. So, a lot of what we're going to be talking about is how this can be accomplished, the speed and the specificity of the nervous system. How can be that be achieved? Then at the end we'll put together how these neurons meet and are organized to get these tasks done. We're going to start off talking about neurons, and their different parts. They can have very different morphologies, but a typical one is going to have a cell body, which is kind of the main portion of the neuron, that contains the nucleus and a lot of the organelles. Then coming off of that cell body are cell processes called dendrites. These dendrites receive information. There can be thousands of them on neurons. So there can be many, many dendrites. All receive information. We'll learn more about how that happens. Then often a neuron has a single axon. You can remember axon starts with an A, it usually takes information away from the cell body of the neuron. Often it has a single axon that's taking information away from the cell body. Where the axon meets the cell body is called the initial segment of the axon. In future sessions, we'll talk about the significance of the initial segment of the axon. Then, often, the axon can branch to form different terminals. We'll be talking about those in future sessions, as well. There's only a few other types of supporting cells. They are called glial cells, that we're going to talk about. One type of glial cells are Schwann cells, which are found in the peripheral nervous system. 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. These Schwann cells are there to support more specifically the axons of neurons. What they do is they form this extension of specialized membrane and then wrap and wrap and wrap around a specific segment of an axon. Each one of these blue structures is a separate Schwann cell that's wrapping around that portion of the axon. They leave little spaces between themselves. We'll talk about the significance of that in future sessions. 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. This acts to electrically insulate that portion of the axon. So the schwann cells are the cells that myelinate in the peripheral nervous system. 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? That's what's shown in this diagram. 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. We will consider in future sessions why that's important. 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. There's just a couple other cell types I want to mention. First are microglial cells which are immune cells of the central nervous system. Then another really important cell type that we're not going to talk much about, but it's becoming increasingly clear that they're very important in supporting neurons, are these astrocytes. They support neurons metabolically. They maintain the extra cellular environment of the neurons. 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 where they support neurons. So this is the end of our first video where we talked about neurons and glia cells. Neurons are going to be the cells that transmit the information. We're going to talk about how that's going to happen in the next few sessions. The glia cells are going to be what provide support to neurons in multiple different ways.
