 While you might actually be feeling overwhelmed by the quantity of content in this first lecture, hopefully what you'll see is that there's a pattern, and we're repeating the pattern, and you see it again and again and again, and we'll continue to do that throughout the entire session on the nervous system. So yes, it is a lot of information right now, but it's building the foundation for your understanding. So right now, we're going to repeat what we just did. You just learned that, you know what, there are different structural divisions of the nervous system. We have the central nervous system, and we have the peripheral nervous system. So central nervous system included who? The brain, which looks something like this, and who else? The spinal cord, which clearly looks something like that. This is the central nervous system. Only neurons that travel within this structure are included in the central nervous system. The peripheral nervous system was anything that went out. Oh my gosh, that looks like a little butterfly. Maybe it'll look... focus. This is the peripheral nervous system. Look how disciplined I've become. Right now, I want to just take a closer look at the afferent nervous system. So let's just look at incoming information. Now, does information come into your central nervous system from just one side? No, not even close. Information travels into your central nervous system from all over the place through all sorts of nerves to get there. But to simplify things, I'm just going to draw a map from one side. There are two flavors of afferent information, which means that there are two flavors of afferent pathways, keeping in mind that the afferent pathway is nothing more than neurons. Now, I'm telling you that this is an afferent pathway. So you tell me which direction is information traveling? This is easy. You know this. Done. Information has to be traveling this way because it's an afferent pathway, which means this is your dendrite and this is your axon. And our cell body, I've drawn it this way on purpose. This will make sense as we go. Afferent information, we have to have some kind of something out here receiving information. And you actually have specialized receptors. You have specialized dendrites that pick up sensory information from the world. You have sensory receptors. Your eyeballs are a giant sensory receptor that pick up light information and take it to your brain to be processed. Your skin is full of sensory receptors that pick up temperature and touch and pressure. Tickle. All of that is transmitted to your central nervous system. But how did it even get started? Well, there's some kind of little receptor out here that said, oh, here's some information. If the information that is traveling in is conscious, if you're conscious of the information, whoa, that was a really pretty light. That's a really hot piece of metal that is on my hand. That is a cold room that I'm sitting in. That information is conscious. Like, I'm aware of that sensory information or it has a label. It is somatic sensory. Now, information can be somatic sensory. A neuron that carries somatic sensory, somatic. A neuron that carries somatic sensory information to the central nervous system can be described as somatic sensory. So a neuron can be somatic sensory. The information can be somatic sensory. Sometimes we call this neuron, this pathway a fiber. The fibers can be somatic sensory. The bottom line is that you're conscious of the information and it's traveling toward the central nervous system. That's one flavor. If somatic sensory is one of them, what's the other one? Look, it looks exactly the same, only a little bit different. Very useful piece of information. Well, it's probably not conscious. And guess what? That's true. And it's called visceral sensory. And visceral sensory, you can actually abbreviate it as VS. And you can abbreviate somatic sensory as SS. And this, again, is describing the kind of information that's traveling in, the kind of afferent information that we're dealing with. Visceral sensory fibers, visceral sensory neurons, can travel from your heart or your blood vessels or your guts. You're not really aware of the fact that you need to change your blood pressure, but the visceral sensory nervous system is sending information to your central nervous system saying, hey, we're about to pass out over here. Why don't you increase the blood pressure? Somatic sensory, again, is just things that we're aware of. We're just conscious of this. The anatomy of somatic sensory and visceral sensory fibers is very similar. You can't really tell them apart unless you see where the information is coming from. So we could throw in like a little heart here. And information from the heart is going to be visceral sensory. We could throw in a little eyeball here. Look at my little eyeball. That's an eyeball. With eyelashes, it looks just like a neuron. We'll throw some eyelids on there. That looks like a really tired eyeball. So that is your conscious sensory information is coming in. I think that's everything you need to know about the afferent nervous system. Shall we do the different flavors of the afferent nervous system? Why not?