 Because both the endocrine systems and the nervous system can act as integrators in various physiological pathways, you should know what the differences are, what are the characteristics that we're going to see in these integrating systems. So the first thing that we want to look at is, what is the message? They're integrators, but how do they communicate? And in the endocrine system, hopefully you're like, dude, I got this, the endocrine system communicates by hormones and hormones are chemical messages, right? That makes perfect, and that's it. So some gland that's involved in the endocrine system is going to secrete a chemical hormone into the blood, dump it into the blood and send it off to do its business. And that's what makes it endocrine. In the nervous system, the message is in the form of an action potential, and don't worry, I believe potential, I think this is the topic of our next one, and action potential is electricity, and that says electricity. Action potentials are electrical messages that travel down neurons, which are the primary cell in the nervous system. The electrical message is not the end of the story, there also is a chemical component of the nervous system's communication techniques, and that's called a neurotransmitter, and this is chemical. So see me right, Kim, right there, I fit it in. Endocrine, only chemical. In the nervous system, we've got an action potential, which is electrical, and the neurotransmitter, which is chemical at the end. So you can see that our messages themselves are different. Now, there's a couple of differences as far as like who's getting the message. Talk about the effector, who is the target. In the endocrine system, the target is anyone. In the story, anyone who has a receptor that matches the hormone that got dumped in. So if a no-cell has the receptor, then the no-cell can be the target. If the stomach has the receptor, then the stomach can be the target. So it's a general, the endocrine system acts generally. In the nervous system, it's extremely specific. The neuron has to touch. Now, I say touch, and I mean that vaguely. They're not actually making contact most of the time. Most of the time, there's a space between the neuron and the effector, but that space is like really tiny. And so for all intents and purposes, especially compared to the endocrine system, they're basically touching, neurons touch the effector. So the target is super specific. Like if you do not touch, if the neuron does not touch the effector, then that effector is not going to be a target of that neuron. There is some speed questions here. The question is the speed of information getting out, information transmission, and the speed of the effect. So let's do transmission. How quickly does the message get out and effect? How quickly does the message translate into action? And here's the bottom line. The endocrine system is slow. We love it anyway, but it's slow. Nervous system, holy fast. You know that action potential that we were talking about? This crazy talk, 268 miles per hour? What? That's crazy fast. So the message, when there is a neural pathway involved in any kind of system, the message from the neuron cell body all the way to the effector, that message can travel at 268 miles per hour. It'd be really interesting to calculate the speed of a hormone and how quickly it can go through your whole body. I want to say that your blood travels through your whole body in like a minute. And of course, that's going to vary depending on how quickly your heart is beating, so how active you are. But a minute to get to a target, and even then, like, did the hormone actually hit the receptor that it was supposed to hit? A minute to get all the way through as opposed to whatever it would translate into if it's going 268 miles per hour. The nervous system is a lot faster. This is interesting. The effect duration, like, how long does the effect last? And in the endocrine system, it's long lasting. So when the endocrine system acts on something, it stays acted upon. The nervous system, the message goes out, the information is barfed, the effect is immediate, and then it goes away. If you want to keep the effect happening, you have to send another message at 268 miles per hour. So how do you say this? The nervous system message is short lasting. I know there's a better way to say that, but it's quick. It's almost instantaneous. It happens at that speed, and then it stops. So if you want to get another, if you want to see it again, you have to send another message. And that actually relates to the intensity of the effect. And how you can actually increase the intensity. So if you wanted to amplify the effect, for example, you send one action potential down your little neuron effector to try to get something to happen. If you want more effect than that, well, all you're going to have to do is increase the number of action potentials. And they're super fast, so you can. And you can actually get kind of an exponential increase in effect if you fire, fire, fire, fire your action potentials really fast. To increase the effect of the endocrine system response, you just need to increase the amount of hormone. And that there's a whole feedback system responsible for making that happen. Now, the rest of this entire lecture, we're going to focus just on the endocrine system. So we're going to start out by looking at, dude, what is this hormone that you speak of? And some of that's going to feel like review. There actually are multiple different kinds of hormones. We're going to look at them, how they differ in their chemistry, and then how they differ in the effects that they come up with. We're going to look a little bit at some anatomical structures that are important in the endocrine system, at least at this point for us. We're not going to spend a huge amount of time talking about endocrine anatomy because the endocrine system really is, we will see it, we will see its involvement throughout this entire semester. It's involved in pretty much everything. All right, let's talk about hormones.