 there are two main ways that cells can communicate with each other. And they're chemical through chemical signals or through electrical signals. And some cells actually communicate with each other via both types of signals. I'm going to give you some examples here. And then you can actually figure out, like, how is this even related to communication. Think about the fact that we've talked about pathways. We know that somehow information has to be carried from place to place. Sometimes that information is in chemical format. Sometimes it's in electrical format. Either way, the cell knows how to interpret that message. A responding, receiving cell down the line somewhere knows how to interpret and understand the message that was sent. And if you think about that, if they don't understand the message, then something is wonkadoosy. And if you've got wonkadoosiness going on, you probably aren't maintaining homeostasis very well. Okay, tools for communicating with people in your body. Tools to communicate with cells in your body. Okay, this is somebody familiar. Do you remember our gap junctions from the last lecture? Gap junctions are tunnels between cells and because cytoplasm can move between cells, gap junctions enable communication. In one cell, here's cell A, here's cell B, they're attached to each other, but look, I just put in a gap junction. The gap junction is holding them together, but it's also allowing stuff from one cell into another cell. So I can literally say cell A is going to send a chemical message or an electrical message to cell B and that can be done because we just can share cytoplasm. You can also have, there are some cells that communicate with each other by touching each other. So this is like, I don't know, like they check surface molecules. And I say they check molecules. So the reason why I say it like this is because this is a common form of communication with the immune system. So the immune system is going to come along. Like an immune system cell is going to come along. So it's somebody new and I'm making it look like a giant old macrophage going around and doing his thing. And it's going to have some sort of cellular protein that connects to another cellular protein on the cell and the act of connecting with each other allows for communication. So they connect, let's not say check. They connect surface molecules and when those two surface molecules connect with each other, information passes between them. In this scenario that I've given you, this would be an example of a macrophage coming along and saying, okay, Joe epithelial cell with that receptor, I have this molecule. Do you fit with my molecule? If you fit, awesome, you're cool, no problem. You're golden. If you don't fit, intruder, intruder in the house. And then we initiate an immune response. So actually contacting each other's, like touching each other's faces, is another way that cells can communicate with each other. I'm going to go back and I'm going to do gap junctions allow for chemical and electrical messages to pass. Checking surface molecules is just chemical. Also, you can dump chemicals into the environment. Really? Okay, that makes total sense. But it's a little more novel than you might think. There's a couple ways that that can allow for communication. One cell can dump chemicals into the environment and those chemicals are paracrine signals if they act on the neighbors. So if I dump messages, chemical messages, out into my environment and the messages go and act on just my neighbors, just the people like in my little office space here, then that would be a paracrine chemical signal. And it came from the environment itself. There are also signals called autochrints. Guess who they act on? Auto-self. They act on self. Now this is wild if you think about it, that a cell could produce a message. This is like sending flowers to yourself. So the cell thinks, dude, I deserve flowers. And so it sends out the message, it barfs out the message that I need some flowers and I deserve flowers or hell, I'm just going to go buy myself some flowers. And then in comes that message acts on me. I made it. I deserve flowers. And now the message of flowers, here they are, acting on me. That's an autochrine signal. Chemical or electrical? They're chemical. Dude, I wrote chemical right there. You tell me, are these long distance strategies or like all in the neighborhood strategies? Every single one of these strategies is a local strategy. Those are only going to work on cells in the vicinity. Of course, we actually have messages that have to travel long distances. And those messages happen via, well, in, I don't even know, do I want to say via action potentials in the neuron or via hormones dumped in the blood? Okay, what's the point? The point is that these guys, these strategies are long distance. And I'm struggling with how to say this to you because the fact is we're going to spend, I can't remember, like four lectures, five lectures on the nervous system, on understanding and action potential. On an action potential, what a wild thing. So think about a neuron. And I'm just using your background in anatomy to help you understand this. You know, a neuron has a cell body and then has that crazy, wonky, long axon. And it can go on out and attach to an effector way out there. That is a long distance message. Hormones. Hormones are chemicals just like the perichrons and the autocrines except they're dumped into the blood. That's the definition of a hormone. That's what we're talking about in the next section when we get into the endocrine system. When a hormone gets dumped into the blood, it heads off to La La Land and it will eventually meet up with somebody who has the correct receptor and then initiate its action. But its target is far away. That's actually the definition of it. Endocrine system and nervous system are systems that cover the whole body and allow communication long distances. Gap junctions, surface molecules and local chemicals, these happen at a much smaller scale. Those really aren't body system wide. Okay, so the next thing that we're going to spend the rest of the time talking about is specifically receptors because the fact is that these guys aren't going to be able to communicate jackaloodle unless the cell receiving the information has the correct receptor. That's what jackaloodle means.