Physiological concept of positive and negative feedback | Behavior | MCAT | Khan Academy

Physiological concept of positive and negative feedback | Behavior | MCAT | Khan Academy


Voiceover: 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 gonna talk about. The first is positive feedback. It’s when the rate of process works to
increase a 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 the
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 could be really
toxic. That’s why negative 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 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 are 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. While 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 gonadotropin
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 it’s message
out 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 the release of LH, which causes the release of even more
estrogen, and the cycle continues. So, you can see that chain effect we were
talking about. So, estrogen is produced, let’s write that
over here. Which triggers GnRH and that works to
trigger LH. 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 LH
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 or 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.

48 thoughts on “Physiological concept of positive and negative feedback | Behavior | MCAT | Khan Academy

  1. Thank you so much ๐Ÿ™‚ .. this video is clear and really helped me understand the difference between negative and positive feedback .. thanks and good luck

  2. In the light of physiological experiments, the fact is well established that: the action of the secretions produced by: the sex glands and resorbed [assimilated] into the blood-stream is – primarily, on: the brain and spinal cord.

  3. Thank you! It took you a little over 6 minutes to get me to understand what my a&p professor spent 3 days on and half of the class (myself included) had no idea what the difference was.

  4. now that was phenomenon .. but is it obligatory to have negative feedback against positive feed back – together- always or each can work individually ?thank you ๐Ÿ™‚

  5. well described, thank you. i have used your drawing as a revision reference! but the 'ovary' looks like a fallopian tube? and you have drawn an ovary but it looks like the oestrogen is coming out from the fallopian tube…just saying ๐Ÿ˜‰

  6. thank you so much but what happened to estrogen? is lowing the LH can high the value of the progesterone? then when it is too low, it will wake up again the estrogen? am i correct?

  7. i am looking for feedback loop in the terms of marketing and business but i stumbled upon this. after watching this video, i have no idea what is happening…

  8. Argh f am I the only dude he can not listen to the period cycle , holly shit it gross the shit out off me! These female shit is gross as f.

  9. But what about all other hormone
    The hard thing about feedbacks is that each hormone have different concept and path to take it like
    TSH or FSH and LH for male !๐Ÿ˜ซ๐Ÿ˜ช

  10. Yes I'm 1kth liker of this video.. ๐Ÿ˜Š๐Ÿ˜Š๐Ÿ˜Š๐Ÿ˜Š… It's a really worth while video.. ๐Ÿ˜Š๐Ÿ˜Š Thank you..

  11. the Video content is quite good enough but pls make sure to use a male voice instead of using female. I feel uncomfortable with her sexy voice -_-

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