 We're going to start by talking about the kinds of sensory receptors that pick up sensations of touch, pressure, or vibration. And here's the thing. All of them are picking up, all of those sensations are felt, are received, are delivered to the central nervous system with the same kind of receptor. And it is called a pysinian corpuscle. Dude, how awesome is that? And wait till you see this thing. No, pysinian corpuscles are amazing. And here's the thing, if you just feel touch. Now, they're embedded in your skin. If you feel touch, the pysinian corpuscle is at the surface of your skin. And if you feel pressure, I mean, think about that. It kind of makes sense. If you just are feeling touch, that is only going to be detected by a sensory receptor that is close to the surface. But if you're perceiving sensations of pressure, in order to get the pressure sensation, you'd need to deliver the stimulus deeper. So pressure is picked up, sensations of pressure are picked up by pysinian corpuscles that are found deeper in your skin. And then vibration is nothing more than these guys being stimulated like many times in a row, you know? Like, that's vibration. But all it is is pysinian corpuscles getting the message. Now, take a look at these things. It's going to make you want to cry because it's so cool. That's what they look like. They're like little endings of the nerve that are wrapped in these connective tissue pouches. And then when the connective tissue is squished or misinformed by a mechanical stimulus, it triggers an action potential. It triggers that action of squishage, triggers the action potential that gets sent to the central nervous system. I'm going to show you what they look like in real life. Do you love histology? Oh my gosh, don't you want to go like find those things? I think I might like fall out of my chair and cry if I found something like that in a histose slide. So cool. Okay, there's another concept that I want to talk to you about when we're dealing with sensory receptors in the skin, and that is this. This is kind of a bizarre concept. And it's that sometimes, okay, visualize this. I'm going to go with sensory receptor, and I'm just going to draw little Pacinian corpuscles because they're cool. So here are a bunch of Pacinian corpuscles. So these are all just sensory receptors, right? Okay, sometimes. Now, this is just somebody's skin. Sometimes sensory receptors all converge on one inner neuron. I can't draw it like that. I have to draw it like this, right? Does that work for you? That's a nucleus. This is an inner neuron. It kind of looks like those little yellow guys in that movie that my kids are obsessed with. Now, if you activate, this is crazy. If you activate this Pacinian corpuscle, you're going to send an action potential to this inner neuron. The inner neuron is going to say, oh, touch. And the touch message is going to go to the brain and you're going to perceive, oh, touch. You, at the same time, touch and activate this Pacinian corpuscle. It's going to send a message to the same neuron, to the same inner neuron. One inner neuron is receiving all the information from multiple places. And the perception in your brain is not just touch. It's one touch. Not two touches, it's one touch. Now, imagine that I could set up exactly the same scenario. See, I'm drawing my four Pacinian corpuscles. Except this time, I'm going to have them converge. I'm going to have them divided into groups of two. And they're going to converge. These two are converging on an inner neuron and these two are converging on a different inner neuron. So in this scenario, if I touch two places, guess what the perception is going to be in your brain? One touch from this message, from this inner neuron and one touch from this inner neuron. We're actually going to mess with this in lab and play with the idea of this is called your two-point threshold. You can't imagine that if this is like your, I don't know, your back. Your back has sensory receptors that are all converging on one place. You don't have to be crazy sensitive on your back. Your lips, don't you agree that your lips are way more sensitive? Your two-point threshold on your lips is going to be much smaller than the two-point threshold on your back. And that's just because of an anatomical phenomenon of how those sensory receptors, which actually are neurons in this case, are set up. Those are organized with the central nervous system. All right. This is general senses. This was just an example. We could go on all semester long talking about all the different cool, amazing ways that information is picked up from the environment. But we're going to move on and we're going to look at taste.