 Hi, you guys. Today we're going to talk about, we're going to start a pretty in-depth review of different parts of the nervous system. And so I thought, what a great time to talk about the required anatomy for this session. So there it is. Shouldn't be a problem at all. Just memorize all those different parts. Right? Just kidding. If you have a sympathetic nervous response, this is more the degree of anatomical specificity that we are going to reach in our physiological conversation about nervous system. So just relax. This first section, we're actually going to talk about an overview of the nervous system, just so you can have everything in perspective. We've already done the neuron. You know how a synapse functions. You know how information travels through our neuron in the form of an action potential. And now we're going to look at, well, how does the information get turned into an action potential? How does sensory information get turned into an action potential? So let's draw a picture of, oh, what do you know? The nervous system. And we're going to do this Wendy style. This is my central nervous system. The central nervous system is an anatomical division of the nervous system. And it's anatomical because it includes the brain and the spinal cord. And the central nervous system only includes neurons that stay inside the brain or the spinal cord. If neurons come out, even if a piece of them is in the central nervous system, then they're going to be part of the peripheral nervous system. Peripheral nervous system is out here. And keep in mind that I'm just drawing my little, I don't know, little visual here, but I want to make sure that you're cool with the fact that a neuron can start in the central nervous system, but as soon as it leaves spinal cord or brain, it's now considered part of the peripheral nervous system. The nervous system also has divisions based on the direction that information travels. Now, I am going to draw sensory or afferent, whoa, pathways on my left side of my drawing, and I'm going to do motor or efferent pathways on the right side of my drawing. Please look into my eyes. Sensory information does not just come in through your left side, and motor information doesn't just come out on your right side. This is purely to keep our brains able to process this new information, so just relax. We know that this is our task today. We're going to talk about the afferent nervous system. We know that in some, like how, what the whole thing has to start with some kind of stimulus, right? And the whole topic of today's lecture is to figure out how does that stimulus get interpreted by some kind of sensory receptor, and then how does that information in the sensory receptor get translated into an action potential, where the action potential sends the information, okay, to the central nervous system. I have to do it anatomically correct, like a, like a this, and then look. It's going to do a little synapse like that. So we're going to receive information. This right here is an afferent neuron, and you can see that it's going, these are like dendrites, and they're somehow connected to that sensory receptor that picks up the stimulus. Here's the amazing thing. Sometimes these little dendrites actually are the sensory receptor. Other times the sensory receptor is a whole nother thing, regardless, somehow the information gets translated into an action potential. That says action potential, even though you can't see it at all. All right, I'll change the color of my action potential. Okay, and then you get into the central nervous system where, oh, who knows what's going to happen? Look, whoa, that's your brain. If we want something to happen, then we need to translate the information. The central nervous system is going to integrate that information, and then we're going to need to translate that into an action. The action message, the message that says, hey, we need you to do something. That message is carried through the afferent nervous system. And if my effector is skeletal muscle, then this is a somatic motor neuron, and the information is considered, it is considered somatic motor, and we will have some sort of skeletal muscle action from the message. But not everything is somatic motor. You can actually have visceral motor responses, and the visceral motor response is, the effector in this case is going to be cardiac muscle, smooth muscle, or glands. Visceral motor, again, we have a cell body in the central nervous system, and the anatomy in a visceral motor pathway is a little bit different, and we'll talk about that in the next lecture. So we're not going to talk about that right now, but I just want you to have an overview of what the afferent path looks like and what the afferent path looks like. I think that's everything that you need to know about the nervous system overall, but this time, today, we're going to look just at the afferent. Really, we're going to look at this right here. How does this stimulus get translated into an action potential that heads to the central nervous system? We'll start out by talking about these sensory receptors. What are they? What flavors do we have? And fun things like that.