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Current time:0:00Total duration:6:33

Physiological concept of positive and negative feedback

Video transcript

in this video we're going to explore positive and negative feedback in terms of physiology so many molecular and physiological processes are controlled by feedback mechanisms there are two types of feedback mechanisms that we're going to talk about the first is positive feedback it's when the rate of process works to increase the product we can think of this as a domino or chain effect so the process will work to increase one product which will then go ahead and stimulate the production of another product and so on the opposite is negative feedback or when the rate of process has to be controlled to prevent the accumulation of a product negative feedback works to decrease a product so that's important because if we have an accumulation of a product in our blood for example we can't have it build up to excessive levels that can be really toxic that's why feedback mechanisms are put into place to control the process that's increasing the product so it will work to inhibit that process by decreasing the product let's look at a physiological process that uses positive and negative feedback and more specifically occurs in females so the first structure here in blue is called the hypothalamus the hypothalamus as you may have heard in your studies is the master control gland of our endocrine system now it's signals or basically talks to this next gland here the pituitary gland the pituitary gland is further broken down into two lobes the back lobe is the posterior and the front lobe that we're going to focus on is the anterior pituitary now moving down we have another organ called the ovary so females have two ovaries that are located way further down in the body well the hypothalamus and the pituitary gland are up in the brain now I've also color-coded these four hormones that we're going to talk about so that way we can keep them straight as we go through the process the first is estrogen the second is GnRH or ganado tropen releasing hormone the third is LH or luteinizing hormone and the last is progesterone so let's start during the menstrual cycle and more specifically before ovulation small amounts of estrogen are secreted from the ovaries this small amount of estrogen is just enough to trigger the release of two other hormones so it stimulates the release of GnRH from the hypothalamus and also works to stimulate the release of LH from the anterior pituitary so this is an example of positive feedback because the process that stimulated estrogen also stimulated the release of GnRH and LH so GnRH can also then work on the anterior pituitary to stimulate the production and release of even more LH into the blood so here's positive feedback again the hypothalamus communicates its message down to the anterior pituitary now LH can also go ahead and stimulate the release of even more estrogen again positive feedback so here we have a cycle estrogen causes the release of GnRH which causes a release of LH which causes the release of even more estrogen and the cycle continues so you can see that chain effect we're talking about so estrogen is produced let's write that over here which triggers GnRH and that works to trigger a now GnRH and LH are going to be accumulating in our blood due to positive feedback so when high amounts of LH are produced in the blood another hormone will wake up so to say and that hormone is called progesterone so progesterone is triggered when it senses that these LH levels are too high and it's secreted from the corpus luteum after ovulation so after ovulation the progesterone will trigger the gnrh production in the hypothalamus to turn off and then that will also trigger Elish production in the anterior pituitary to also turn off so can you guess what this is called if you said negative feedback then you are correct since the levels of product are becoming too high in the blood something needs to cause an inhibition of those products that way they don't accumulate in the blood that's why progesterone comes in and turns off that positive feedback process and decreases the products that's where we have an example of negative feedback in this specific physiological mechanism going back we can see that the LH caused the production of progesterone or the secretion of progesterone in the first place and then progesterone is going to go back and work on inhibiting further GnRH and LH release as you can see in this little cycle so that's how we maintain homeostasis or balance in our body which is really important for maintaining molecular and physiological processes that way nothing in our body becomes too out of balance too high or too low that's the beauty of physiological feedback