Now we're going to talk about feedback loops in the body. We're going to do this because homeostasis is largely controlled through feedback loops. A feedback loop is going to occur when a change to the internal environment causes a response, and that response is the feedback part. And the response is going to alter the internal environment. If you remember where we started, we began with a change to the internal environment. We're back at the beginning. That's the loop. There are going to be 2 types of feedback loops that we're going to discuss: firstly is negative. Negative feedback loops move the system in the opposite direction to the original stimulus. In contrast, positive feedback loops move the system in the same direction as the original stimulus. We're going to look at both of these in more depth here.
Let's start with negative feedback. Negative feedback moves the system towards the set point and that maintains homeostasis. That's why we're discussing this first, and we will explore it in much more detail in upcoming videos. We are concerned with maintaining homeostasis because that is going to be one of the major processes that happens in physiology of the body. Imagine our set point here on this little dial. We have a little dial and an arrow pointing up, and it looks like it's fallen off to the right here. Well, negative feedback is going to move the system towards the set point in the opposite direction of the stimulus, so it is going to push this dial back up to where it started. I like to think of this as a person balancing on one leg, and so we have a little image of someone balancing on one leg here to remind you of that. Homeostasis, we said, is standing still in one place, but it's a dynamic process. If you're standing on one leg, you might look kind of stable, but there's all sorts of negative feedback going on. If you lean forward, your body pushes a little back. As you lean one way, you stick your arms out to fix your balance and you come back to the center. All of your movements are going to be opposite the stimulus, so you return to your set point. This means that negative feedback kind of self-regulates. It turns itself off. It gets back to the set point, and it's all set. It also means it's going to be more common in the body. Again, we're trying to maintain homeostasis. We're trying to stay at set points. Negative feedback is really good at that.
In contrast, we have positive feedback. Positive feedback moves the system away from the set point. We have our little dial here, and our set point up the middle. Imagine if the set point falls off to one side. What positive feedback will do is just going to keep pushing it farther and farther in the same direction. I like to think of this with the analogy of a fire. When you start a fire, you light some paper, it generates heat. The more heat it generates, the more things catch on fire. The more things that catch on fire, the more heat it generates, and the fire just gets bigger and bigger, just like positive feedback. Importantly, this requires a sort of off switch in the body. You don't want these positive feedback systems to get out of control, as they have the potential to. It also means they're going to be much less common, because moving away from the set point, well, that's not what we want to do if we're maintaining homeostasis.
The last thing that I want to note here is that a misconception some people have is about the terms negative and positive. When we say negative, we often think on a number line, it means going less than. Negative feedback could push something in a positive or negative direction, it just depends on what the original stimulus was. Negative, in this case, means opposite. The same thing for positive. Normally, you think on a number line, positive means more. Well, positive feedback just means in the same direction. It could be that something is getting less, and then positive feedback just makes it get less and less continually.
With that in mind, as I said, we're going to look at negative feedback in a lot of detail, and we'll also examine positive feedback in some detail as well coming up. And I'll see you there.