Hello and welcome to Anatomy & Physiology at Glen Oaks Community College, I'm Dr Ren Hartung
for this video we're going to move further into the endocrine system
this is the first in a video discussing each of the endocrine glands and the hormones that it produces or the functions that it's involved with
for this one we're going to talk about the hypothalamus
the hypothalamus is in the brain
and by the way, I probably won't write much anymore I'm not sure, I do have these videos closed captioned and I go in there and make sure
things are spelled correctly so you might use that if you're looking for spelling
the hypothalamus is here in the brain it is close of course to the thalamus which would be up in this
neighborhood here and the hypothalamus has lots of functions that are very important for example
hunger
controlling body temperature, our body's thermostat is up in here
and it controls this next gland that we'll talk about a little bit now the pituitary gland
the hypothalamus can release hormones that control what's called the interior pituitary gland the front part of the pituitary gland
the hypothalamus also contains some nuclei or small collections of neurons that have an important job
there's two nuclei up in here that produce and, ultimately cause the release of the
hormones that come from the posterior pituitary gland
in order to do this function in order to control the interior pituitary gland and the posterior
specifically for the anterior pituitary gland the hypothalamus makes hormones
and it makes those hormones and very very small amounts because
those hormones only have to travel in little blood vessels between the hypothalamus and the anterior pituitary gland, those blood vessels
collectively are called the hypophyseal portal system
so the hypophyseal portal system is a collection of veins basically, very small veins that can carry the hormones that come from the
hypothalamus down to the anterior pituitary gland where they have their effects
I said the released in very small amounts -- in fact you can't really test for the hormones
released by the hypothalamus in general circulation
because by the time they get into general circulation
they've been diluted so much that they're undetectable so researchers that study those hormones actually have to go into the blood
vessels of the hypophoseal portal system and draw blood from there
obviously we don't do this on humans 'cause this is keep in the skull, can't do it on mice are rats because these vessels are too small
my understanding is-- they do this on sheep-- I think that's one of the animals they use
at any rate let's talk about a couple of the hormones-- first I'll talk about the major classes of them and maybe I will write this
releasing hormones
so these are hormones coming from the hypothalamus that encourage various hormones to be released from the pituitary gland
and then the next one is inhibiting hormones
those would obviously have the opposite effect they would cause a decrease in the release of whatever hormone it is that's been controlled from
the anterior pituitary gland-- to give you-- just to give you some examples
for releasing hormones gonadotropin releasing hormone or GnRH
this hormone released by the hypothalamus tells the anterior pituitary gland to release the hormones FSH and LH
those are the gonadotropins-- the hormones that control our gonads, in women the
follicle stimulating hormone causes follicle maturation so that ovulation can happen
with a mature follicle-- and of course lutenizing hormone
there's a spike in lutenizing hormone that happens and that's what causes ovulation
--- so these are the gonadotropins, oh, in men by the way, both of these are important in sperm production
so that's one example I can give you another example, and that is CRH
also known as corticotropin releasing hormone CRH goes down to the anterior pituitary gland
and causes the anterior pituitary glands to release ACTH
which is adrenocorticotropic hormone
that hormone goes down to the adrenal glands and causes hormones from the adrenal cortex to be released, especially cortisol
so, again big picture here what we're saying is that the hypothalamus has control over the pituitary gland
and it has that control by releasing small amounts of hormones
through the hypophysleal portal system and that controls the anterior pituitary gland and the release of its hormones and let's go back to the posterior
pituitary gland, I mentioned there are two nuclei up in here
and forgive me anybody who knows, but I'm not sure of the exact location
so I may draw these in the wrong relationship but there's two nuclei up here
and we have neurons that are sending axons down into the posterior pituitary gland, this little neuronal tract is called the hyothalamohypophyseal tract
that tracked leads into the posterior pituitary gland
when these neurons up here in these nuclei, when they undergo action potentials
those action potentials lead to the release of the hormone from the posterior pituitary gland, very similar to what we see with neuronal
communication where an action potential comes down an axon and when it reaches the axon terminal we
get the release of neurotransmitters that then cross a synapse and communicate with another cell
in this case when these axons undergo action potentials
the axon terminals instead of releasing a neurotransmitter they release the hormone
the two hormones that are released in response to that antidiuretic hormone has an effect on the kidneys
and the other one is oxytocin
notice that we've talked about some of the hormones from the pituitary gland
but there's a lot more so I'll do that in a different video, again the major thing
here is to understand how it is that the hypothalamus controls the pituitary gland
via--- again, just for the purpose, the hypothalamus
controls to secretion of hormones from the pituitary gland
it controls the anterior pituitary gland
through the release of hormones from the hypothalamus that travel through the hypophyseal portal system
and influence hormone secretion by the interior pituitary gland
and then for the posterior pituitary gland there's actually neurons that come down into the posterior pituitary gland and bring about the
release of the two hormones from the posterior pituitary gland
Oh, there's other one I like to talk about, if you get the major point you're probably good
but there's one more that I'll talk about that has to do with metabolism
there's other releasing hormone is released by the hypothalamus and this one's called TRH
thyrotropin releasing hormone
when TRH is released by the hypothalamus it comes down to the anterior pituitary gland and causes the release
of TSH, thyroid stimulating hormone
and TSH then goes to-- I'll try and run the thyroid gland here
there's it's little isthmus--- the thyroid gland then releases T3 and T4
these two hormones
act systemically on the body causing an increase in metabolism
an increase in energy usage, one of the things they do is cause
almost all cells to increase their production of the sodium/potassium pump,
and that pump gets placed into the membrane of the cells, and if there's more
than are needed then those sodium potassium pumps still do what they do and if you recall
they use ATP to pump sodium of the cell and potassium into the cell
if they're doing that more than a need to there other proteins that help regulate and
make sure that we don't have too much sodium on one side and potassium on the other
ultimately those sodium/potassium pumps are just spinning their wheels and burning energy
as a result they produce heat
so here's a fun story to go along with this lets imagine that you're out in the wintertime
and it's very cold outside in your sledding were skiing or something
you may notice if you've done is that the first half an hour maybe hour that you're out in that cold you feel
cold you might shiver home and it's kind of uncomfortable
but once you've been out in the environment for a while especialy if you if you're physically active but
even if you're not physically active what you've done in that environment for over an hour so
your body starts to adapt to the cold and you don't feel as cold any more, you still feel that it's cold outside but you are more comfortable
here's one of the mechanisms that help to make this happen so that your body is generating
the heat it needs to be in that environment relatively comfortably
your brain especially obvious that hypothalamus where the thermostat is it detects that the body temperature is low
it releases TRH, the TRH stimulates the pituitary gland to release TSH the TSH causes the thyroid
to release T3 and T4, the T3 and T4 increase your body's metabolism and you make more heat
so I like to talk about that as kind of a fun story to understand
not just how this works in the technicals of what the hormone names are, the mechanisms, but
related back to real world so you can see why this is important
and we've already talked about why GnRH is important otherwise reproductive function is in trouble right
so that last bit, I call those little things "why we care" why do we even want to know about this
apart from it's just cool to know from a geeky science standpoint
that's all I want to share with you about the hypothalamus and I'm going to get to work on talking about the pituitary.
If you have any questions about this video or anything
please go ahead and submit questions down the comments below or make comments if you'd like
and thank you once again for watching