Feedback Regulation

by Jason Amores Sumpter
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regulation is super important. Thio all metabolic and physiological processes. One of the best strategies for regulating is known as negative feedback. And this is a type of regulation where the output of a system will actually reduce the systems output. Now, that's kind of ah, confusing general way toe put it. So let me give you an example. That kind of makes this a lot more clear. Here we are looking at like Hollis ISS, which is the first step of cellular respiration and a super important process. No matter what type of biology you're doing now, you don't need to worry about memorizing any of these names or technicalities. You'll have plenty of time for that. If and when you take biochemistry. I just want you to get a sense of how negative feedback works. So, like Hollis is begins with glucose and you wind up with pyro of it. In the process, you produce Sameh tp right now. Like Collis, this is the first step of cellular respiration, which ultimately results in the production of a lot of a teepee through oxidative phosphor elation. So a teepee is not only a direct product of like Hollis iss It's also the major downstream like endgame product that this whole process is gunning for. So, like Hollis ISS is under, uh, negative feedback control. The way this works is one of the enzymes that catalyze is a reaction very early in the process. It's a very important step of the reaction for reasons that you don't need to worry about these enzymes called phosphoric geekiness, and it is negatively regulated by ATP. So ATP will feedback and shut off fossil for tackiness, shutting down this chemical pathway. So essentially, if there's too much ATP being produced either directly from like Hollis ISS. But more likely, you know, through the downstream cellular respiration. Oxidative sorry, the downstream oxidative phosphor elation process. Um, if there's too much a teepee being produced, it's going to negatively feedback and shut off the very beginning of this whole process to conserve Resource is, you know, not waste energy and just maintain the balance of generating Justus much 80 p as is needed so you can see how powerful and eloquent a system negative feedback is where ah systems output will actually reduce this output of the system in order to control the levels in a nice passive way. Now. Positive feedback is very much so. A different beast, and it's also a lot more rare to see. And the reason for that is because with positive feedback, the output of a system actually increases the systems output, right? So the most common example of positive feedback is in birth, where the infants head, uh, pushes and sets off some receptors that send a signal which induce greater labor contractions, which in turn are going to cause the infants head to push harder against those receptors, which, of course, means more labor contractions. And so these two things just upped the ante and feed back positively on each other, creating a bigger and bigger effect. So you could see why something like that you wouldn't want to use in a lot of systems. It could very easily get out of control, which is why negative feedback is everywhere, and positive feedback is a lot less common now to look at a example of negative feedback that involves actual, uh, systems in the body. Want to take a look at something known as the HP a axis? Now this is going to involve the nervous system and the endocrine system. The nervous system is going to be a A system responsible for transmitting information throughout the body, as well as receiving information from the body and the environment. It's going to transmit the signals via nerves through those electric signals Act called action potentials. Um, if you wanna know more about this, check out the nervous system videos. The endocrine system is also a signaling system, but it functions differently than the nervous system. The endocrine system is a hormone signaling system, so it's going to involve glands that secrete hormones into the bloodstream. And those hormones are going to target and set off reactions at various organs that have their appropriate receptors. So both of these air signaling systems and they're actually connected by this really cool brain structure called the hypothalamus, which basically just means underneath the thalamus, which is where it's located. So very creative naming here. Ah, this structure coordinates the autonomic nervous system, which is going to be the part of the nervous system that we don't have direct control over right things like breathing heart rate, that sort of stuff we don't have direct conscious control over is what I mean, you obviously are. Our hypothalamus is controlling that. So we have We have control. We don't have conscious control. It's not like the part of the nervous system where I can say all right, Finger wants you to poke and move or whatever. So the hypothalamus links the nervous and endocrine system by coordinating the autonomic nervous system. And also by coordinating the pituitary gland, which is a very important gland in the endocrine system and in it has a variety of functions. I don't want to get ahead. I don't wanna get ahead of myself because I could go off on tangents and all of this forever. So here's the important thing to note you have the hypothalamus that is a brain structure, right? And in the h p A axis, which stands for hype of phylum IQ, pituitary adrenal access, right, H p. A. Um, essentially, what you have is a stress hormone, uh, you know, signaling system so the hypothalamus can release something called Kordic Atropine releasing hormone. Don't worry about these names just now. This will stimulate the pituitary, the P in the h p A to release, uh, a C T. H or a Drina Adrenal cortical Tropic hormone. Again like don't worry about these names. Thes air. Just stress hormones. That's all you need to know that will eventually lead the adrenal cortex to secrete and let me jump out of the way here. Cortisol, which is that main stress hormone. Now the thing about cortisol is it actually feeds back negatively to the pituitary and the hypothalamus. As you can see here court, this is standing for cortisol. We'll actually have a negative feedback effect on the hypothalamus and the pituitary to cause them to stop releasing quarter trope in releasing hormone and adrenal cortical tropic releasing hormone. Or, as it's much easier to say, CRH and th essentially the downstream output of that system. Cortisol will go back to earlier points in the system and cause them to shut down that pathway again. This is known as the HP access and is a really nice example of negative feedback regulation. That's all I have for this video. I'll see you guys next time