 Hey everybody, Dr. O'Rear. So we just got done talking about what homeostasis is and the basics of how our body maintains that stable internal environment. Now we're going to look at negative feedback. So there's two types of feedback, negative and positive feedback, but I'll explain why. Almost all of your body's feedback control systems are utilized negative feedback. So let's go ahead and talk about what that is. Negative feedback is, so your body is in this state of stable internal environment, right? Everything should be within normal ranges. Your blood potassium level should be normal, blood pH should be normal, right? So if something changes, that's usually bad, right? Because you should already be perfect. So if you teeter one direction or the other, your body should not like that. So when there is a change and your body's response to that change is to bring it back or negate it, that's called negative feedback. If your blood sugar goes too high and your body brings it back down, negative feedback. Core temperature goes too high, body brings it back down, negative feedback. So hopefully you understand why almost all feedback loops or feedback mechanisms are going to involve negative feedback. I get too much of a hormone, my body stops making it till it comes back down, et cetera. Let's look at an example in the world and then we'll look at some examples in the human body. So here's the typical example in every textbook is how your home maintains temperature. So you probably have some fancy digital thermostat now, but this is what the wall thermostat looked like in my house when I was a kid. So we have our sensors would be the temperature sensors that tell your house the control center in your house here. The thermostat what the temperature is. The thermostat would be your control center and the heater air conditioner are going to be your effectors. So let's say it's set for 70 degrees. You've told the control center you want your home to be 70 degrees. It's more like 63 in my house, but let's say 70 degrees. And so the sensors are watching the temperature. If it climbs to 71 degrees, the control center is going to say air conditioner, bring the temperature back down to 70. If it drops to 69, 68 degrees, then the control center is going to say this temperature is too low heater, bring the temperature back up to 70 degrees. So that's going to be the sensor control center and effectors. That's going to be how your home maintains homeostasis, a stable environment that's 70 degrees, but your body does the same exact thing. So here's how your body would maintain temperature. The sensors, the receptors would be the thermal receptors, your temperature receptors. The control center is going to be in the hypothalamus part of your brain, which is critically important for maintaining homeostasis in lots of ways. And then your effectors are going to be all the things we see here, blood vessels, sweat glands, muscles. So if your thermostat in your hypothalamus says, I want this body to be 98.6 degrees. If it gets too cold, then it's going to tell your body to bring the temperature back up. You're going to shiver, muscles are going to contract. Your warm blood is going to go to your core to get away from your skin and keep your core, especially your liver, temperature elevated. And your thyroid gland is going to up-regulate your metabolism. That's how your body would, your temperature dropped. That's how your body would bring it back up, negative feedback, or, you know, and then if your temperature goes too high, then your body is going to do the same thing. We got to bring the temperature back down. So you're going to move blood to your skin. You're going to sweat and you're going to lower your metabolic rate to try to bring the temperature back down. So here's one example. I'll show you a couple more. I won't go into detail. We'll cover them all when we get to the appropriate area, but I just want you to see this is how your body does almost everything, negative feedback. So blood calcium levels get too high. We have ways to bring them down. Blood calcium levels get too low. We have ways to bring them up and we'll cover all that in detail in AMP2. Metabolism gets, you know, thyroid hormone levels get too low. We have ways to bring them up. Thyroid levels get too high. Have ways to bring them down. Now, of course, there are times this doesn't work, right? Which is why millions of Americans have to be on thyroid hormone replacement. If your body can no longer do this, you now have something wrong with you. And that's when you go to the doctor and get diagnosed and hopefully get treated. Same thing here with water, right? If you don't have enough water in your body, then you're going to be thirsty. And your body's going to conserve water. If you have too much water, then your body's going to find ways to get rid of it. So these are all the different ways that your body utilizes negative feedback. But just remember, there's a change in your body, which is usually bad, because you're perfect. I hope you always remember that. If there's a change in your body, you negate that change. You bring it back to normal. That's negative feedback. In the next video, we'll talk about when and how positive feedback works when you would want that to happen instead. I hope this helps. Have a wonderful day. Be blessed.