 Hey everybody, Dr. O'Hare. We just got on talking about negative feedback, now we're going to look at when that won't work. So remember, negative feedback is there's a change and you try to stop that change, you try to bring it back to normal. But positive feedback is needed when we need to see a lot of change. So think emergencies, when things have to happen very quickly and we know exactly what our destination is, we have a defined endpoint, then positive feedback is the way to go. So here you see labor and delivery is one of the two key examples of positive feedback, the other being blood clotting. So imagine if you started to go through the process of labor and delivery, you started to deliver a baby and the body said, wait, this is a change, we don't like change. So it would try to stop you from having the baby, that would be catastrophic. Or imagine we'll cover blood clotting in a moment. Imagine when your blood starts to clot, if your body says, ooh, we don't like change, we need to stop your blood from clotting. These would be catastrophic, these would be disastrous. But on the flip side, imagine if your blood sugar went too high and your body said, oh, let's crank your blood sugar even higher. So positive feedback would not work in most situations. But in emergencies, when something has to happen very quickly, positive feedback is the way to go. So the two key examples of positive feedback, I already mentioned, are labor and delivery and blood clotting. So let's just look at these real quickly. I mean, enormous changes have to occur in a woman's body in order to deliver a baby. And it has to happen super quickly. The quicker you can get this baby out, the better. So that's why we have this positive feedback. So you see anywhere you want to start. So let's start with the bottom there. We stimulate some contractions. So you're already having some contractions. Oxytocin stimulates contractions, which is going to push the head of the baby into the cervix, which is going to send signals to the brain that lead to more oxytocin, which means to more contractions. And this is positive feedback. So the key with positive feedback is every step speeds up the step after it. It's like a snowball rolling down a hill. So this process is going to go, and it's going to get faster, and it's going to build, and it's going to build until this baby comes out. There's no longer pushing on the cervix, and this system would shut down. That's what I meant by a defined endpoint. You wouldn't want this to go on for the rest of this woman's life. You only want it to go on until the emergency getting out the baby is done. So here we see blood clotting, and we'll cover the blood clotting cascade later, but still a really good example. If you're when your blood starts to clot, you want it to clot as quickly as possible. You need an immediate response before pathogens get in or before, excuse me, before you lose too much blood. So the blood clotting process is called a cascade. Whenever I hear the word cascade, I think of that, that snowball rolling down a hill. So the first step in the blood clotting process speeds up the second step, which speeds up the third step. It makes it hard to learn because we have these large, complicated cascades that are used to clot your blood. But in the end, if we didn't have this cascade and all we had was the conversion of fibrinogen to fibrin, your blood would clot a million times slower. So this positive feedback mechanism speeds up blood clotting by a million times. That's pretty unbelievable. So just imagine how important it is in these types of emergency situations that we do have a system that will take us out of normal because having a baby and bleeding are not normal. So it's good that we have these positive feedback mechanisms. OK, so that's negative and positive feedback in these two videos. And those are the two ways that your body maintains that stable internal environment. I hope this helps. Have a wonderful day. Be blessed.