 Okay, so this is a slice of retina. And if that last lecture piece didn't blow your mind, then surely this one will. This is a slice of retina that is not the phobia. So we have several different layers in the retina, and we're going to talk about each and every single layer. The first layer of the retina, okay, no, stop. I'm not going to really reach it down here, but you have to know that light is going to come into this scene in this direction, which makes sense because here are my photoreceptors, my rods and cones. And we'll get there in a second, but look at all this stuff that is between the light's entry point and our photoreceptors. Okay, now let's label parts. We have a layer that is the farthest away from the stimulus, and it's called the pigmented layer. And the pigmented layer of the retina, its essential function is to prevent it's dark, it's full of melanin, and it prevents light from bouncing around and reflecting around the eyeball. So light waves that get past the cones and rods don't bounce around and stimulate other things in these places and mess up your sight, make your sight blurry. So you've got your pigmented layer farthest away from the light. Then you've got your rods and your cones. And you can see here that my rods are the blue guys and my cones are orange. Do you agree that the rods and the cones are actually found in the same layer? These are my photoreceptors, and we've already talked about how they function. So we need light to reach receptors. We need the light to reach these guys first. Now it's about to get funky. Are you ready for this? Because we've got these things called horizontal cells. Seriously, horizontal cells. And horizontal cells, look at how they're set up. They're actually making contact with my rods and my cones. And they reach out and contact rods and cones in a line. And they prevent, really, this is weird, but they prevent crosstalk between the rods and cones. They prevent a stimulus from, they keep it more focused. They prevent the information. They'll inhibit that rod or cone over there that's thinking that it wants to fire a non-message. It'll inhibit it because the light, it perceives the light as being more focused right here. Okay, did you follow that? The horizontal cells prevent, how did I write it in my notes? Lateral spread. You've got to remember, these guys are all sitting in the same extracellular fluid. So any changes in ions, any changes in details of the extracellular fluid are going to affect other cells in the vicinity. So we've got this whole layer that's basically of policemen that are saying, no, that stimulus didn't come to you. So even though you're feeling the funk in the extracellular fluid, we don't want you firing, this wasn't yours. Crazy talk. Okay, you thought that was crazy. How about these bipolar cells? Bipolar cells are just chilling here. They're the ones that information gets dumped on them first from the rods and cones. So basically, they're a messenger, messenger from rods and cones. So they're going to take the message. Horizontal cells are saying, hey, you rod over there, don't you be firing, and hey, you guy over there, don't you be doing anything. But the bipolar cells receive the information directly from the rods and cones and send it on. Sometimes they don't send it on. Then you've got a set of amocrine cells, and it looks like I'm going for, you know, kind of a gray color for these amocrine cells. Amocrine cells. And I love this. I was just thinking in my brain, what do amocrine cells do? They have a huge variety of cell functions that essentially help interpret visual data before it leaves the eye. You go ahead. I mean, I feel like, okay, we could probably have six lectures on amocrine cell function and how those things work. But it's another layer. Look who's connected. My little bipolar cells are connected to amocrine cells, and they're also connected to these yellow guys, which I'm hoping are my ganglion cells. Are they? No. I don't know who the yellow guys are. They start with, I don't know who they are. But that's okay, because we don't have to know them. We have to know the ganglion cells. Because guess what? The ganglion cells, ultimately, through all these layers of don't talk to that guy, and go ahead and send your message, and don't send that message, and that message clearly is irrelevant. All of them putting in their little two cents. The message gets through to the ganglion cells. These guys are who basically become the optic nerve. So if you look, you can't really see it down here at the bottom. But I just circled the optic nerve. They get information. Come on, everybody, tell me what's up. And then they take that information. Their axons become the optic nerve. All the axons from all the ganglion cells in the retina converge on the optic disc and become the optic nerve and exit the eyeball. And that's how the information gets to the brain. If this is like, like wide eyes, like if you look like this, oh my gosh, then you did understand what we just did because it's, it's, wow, we need an eyeball class. Not only that, dude, once this information gets to the brain, there's a range of things that happen to it in there. You are so amazing. Pat your eyeballs and your ears and your nose and your tongue. Oh, that's it. That was the afferent nervous system. Now we're going to do autonomic nervous system next, I think.