 All right, so you'll notice that there's been a small costume change. I've blasted forward into the future about a year. And I'm trying something new. The OCD part of me has a very hard time with the fact that seven parts of this lecture are in one outfit at one time in my life. And the remaining two are going to be in a different outfit at a different time in my life. It's a little painful, but we're going to update those other two sections and try not re-recording the entire sequence. We're going to talk about pathways. Hopefully at this stage in the game, you're like, dude, do we ever talk about anything but pathways? If that's your sensation, then you've been paying attention. You're in good position because, no, we talk about pathways a lot. So far in this lecture, you have a whole bunch of strategies for a bunch of different tools that cells can use to coordinate action. And if you think about it, there's got to be a reason, like why are we coordinating these actions? And who's coordinating the actions that are being coordinated? And that's where the pathways come in. Every organ, every cell is going to have mechanisms and things that we're going to learn about. But really, none of them operate in a vacuum. All of them interact with other cells in the body. And sometimes those interactions are homeostatic. Sometimes they're not, but there is a lot of working together. So our treatment of pathways right now, we've seen it in a homeostatic perspective. But now we're going to get a little more broad so that we can fit any communication pathway, whether it be neural. We spent six lectures in anatomy talking about neural pathways and the anatomy of those communication pathways. It gets more complicated, it gets more lovely in physio, and so we need kind of a more broad way of looking at a pathway, a communication pathway. And again, if you have been conscious or present in any part of the rigs style classes, then this is definitely going to be familiar to you. And it never hurts to do it again and again and again in all of our different contexts. In fact, today's lab is nothing more than jillions of pathways in which you will be identifying the different parts of the pathway. Okay, so let's take a look at communication pathways. And again, in lecture number one, you got information to help you figure out is this pathway homeostatic? In this one, we're just looking at pathways in general. Not all of them are going to be homeostatic. Every, there's three parts to every pathway. All of them have these three parts. And so I'm going to give them to you. In fact, we'll do it like a like of this. We have some sort of input. You know what? I'm going to do it in the middle here. We have some sort of integrator. And we have some sort of output. And these are my three components of every possible pathway. Input has to begin with a stimulus. Am I right or am I right? We got to have a stimulus. And the stimulus is like what starts the input. The stimulus can be internal. It can be inside your own body. It can be external. Something in you has to detect the stimulus. So there has to be some kind of a sensor. Do you agree with that? Sensors can be sensory receptor organs like your eyes or your nose or your ears. They can be actual parts of a neuron. And sensors can be endocrine structures. They can be cells. They can just be Joe cell. They can be immune cells. Sensors pick up that stimulus. Somehow the stimulus initiates a change in the sensor. How does it initiate the change? That's physio. That's what we're doing in this class is to figure out how that happened. So the sensor picks up the change and generates, I knew that word would come to me in a second, and generates some kind of basically a message that is sent to the integrator. Now, if the sensor is a neural structure, then the input message, it travels along a neuron through an afferent path. I'm just going to put a little note here that this section right here, I'm going to put a green arrow. If it's a neural pathway, that's the afferent path. Afferent, that says afferent. If we're talking about a different kind of pathway, like an endocrine pathway, we don't have an afferent path. An afferent path is an actual anatomical structure. It's a nerve. And endocrine pathways don't send messages via nerves. Pathways can get super complicated and involve endocrine aspects and neural aspects. So this is only, it's only considered an afferent path if it's a neural. But for perspective, since we've spent so much time talking about our pathways, it helps to have this perspective. But the message can, there's all sorts of different ways that we can get the message to the integrator. As you know from endocrine systems, sometimes the sensor actually is the integrator. And again, so a sensor could be an actual receptor. So it could be a full-on receptor organ or it could be a cellular receptor protein. And that receptor protein could be on an integrating endocrine cell. It's really legit and that's a great pathway. The integrator receives the message and then the integrator does the processing and the integrator is the piece that stays the most consistent like the terminology is the same. Integrator is an endocrine structure or the central nervous system. And it's where the afferent path comes and the afferent message comes in and the processing happens and the integrator coordinates the output message. So the integrator is going to send, what color shall we do this time? Some sort of message, some sort of output message. And look, the output message, who does that go to? Let's make a note that if we're in the neural pathway, this is my afferent path. The afferent path can be a nerve. If you don't have an actual anatomical structure, you really don't have an afferent path. But we can still send messages because integrators can be endocrine glands and endocrine glands send out hormones through the blood. That's, we're talking endocrine system in the next lecture so we'll get more details on that. Okay, so the output message gets sent. The integrator is saying, hey, we had this stimulus. Now we need to do something about it. The output message goes to whom? Doggies of a feather. It goes to the target. Now, here again, if the target is, if the afferent path, if the output message is an afferent path, then the target is going to be an effector. These green things are terminologies that are only for neural pathways. The effector, an effector is not affected by the endocrine system. The term effector is specific to the nervous system, a neuron synapses with an effector. You can think of the effector as a target. That totally works for you and the target is going to be anybody. We know effectors are smooth muscle, any kind of muscle or glands. A target can be any other cell that has the proper receptor to be able to pick up the information that's being sent. The target is going to carry out an action, whatever the target is. So, if the target is a muscle, the action is probably contraction. If the target is a bone cell, the action might be to digest bone tissue. What kind of cells are digesting bone tissue and like breaking it down? It would be the bone crushers, osteoclasts in the house. So, your target is whoever is going to do the deed. Now, we have to introduce the idea of feedback loops because now you have a pathway. Well, we have to talk about the different kinds of feedback that you can have in such a pathway. That is assuming I can turn this off.