The endocrine system is a complex network of glands and hormones that regulate various bodily functions through chemical signaling, acting as a slower but longer-lasting communication system compared to the nervous system.
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hi everyone dr mike here in this video
we're going to take a look at the
[Music]
now the endocrine system is a collection
of cells and glands that produce and release
release
hormones these hormones are just
chemicals that jump into the bloodstream
and have their effect in distant areas
of the body
now it's a communication network similar
to the nervous system that controls
physiological activity but it's a little
bit different it's different in the
sense that the nervous system
is very fast it's very direct and
usually it's short acting
the endocrine system is the opposite so
it's quite slow to have its effect
it isn't direct because it jumps into
the bloodstream and travels to very
distant areas of the body
and it can last a long time some
hormones when they're released
can have their effects that last hours
to days to sometimes
weeks so in this video we're going to go
through some of the important
cells or glands that produce and release
hormones and go through
what these hormones are and have a quick
look at their activity or function in
the body
we're going to do this a top to toe
mechanism start at the top and move our
way down so to begin we need to start at
the brain
specifically at the base of the brain
there's something called the
hypothalamus which is telling you
it sits below the thalamus this is the
hypothalamus it sits here
we've taken it across here here's the
hypothalamus and you can see that there's
there's
an extension of the hypothalamus that
has two lobes to it or two parts
this is called the pituitary gland and
that's another endocrine
tissue or gland that itself produces and
releases hormones
the hypothalamus produces another a
number of hormones
that has its effect to control and regulate
regulate
the endocrine system of many other
tissues of the body so we call the hypothalamus
hypothalamus
the master regulator or the control
center of the endocrine system
now five important hormones that the
hypothalamus produces
and releases to control many other
aspects of the endocrine system
these hormones are thyrotropin releasing hormone
hormone
corticotropin releasing hormone growth
hormone releasing hormone
prolactin releasing hormone and
gonadotropin releasing hormone so a
couple of points here
releasing hormone tells you it goes
somewhere else
to release a hormone all right makes
sense also
tropon as a suffix tropin sitting at the
end of the word
if you see a hormone with tropon as a
suffix it means it's going to go to
another tissue of the body to tell it to
release another hormone all right
so how does this work well the hypothalamus
hypothalamus
talks to both aspects of the pituitary gland
gland
posterior and anterior but interestingly
the anterior is connected to the
hypothalamus through a blood supply
which means the only way the
hypothalamus can talk to it is it
releases hormones and they travel
through this blood supply to tell the
anterior pituitary gland to release its hormones
hormones
the posterior pituitary gland is
connected to the hypothalamus through
nerves which means the hypothalamus
doesn't need to release hormones to tell
the posterior to do it
it just sends a nervous signal down to
tell the posterior to release
hormones all right these hormones
that are named here that the
hypothalamus produces
moves through the blood supply to the
anterior pituitary
to tell the anterior pituitary to
release a number of hormones
number one the hormone that is told to
be released from the anterior pituitary gland
gland
the second hormone now there's no
particular order i'm just
ordering it here for ease basically but
there's no particular order
but the second hormone that's released
and the fifth is the gonadotropin
gonadotropins and there's two
gonadotropins you need to know
and follicle
all right what happens
thyrotropin-releasing hormone released
from the hypothalamus
stimulates the release of thyroid
stimulating hormone
this is a hormone that now jumps into
the bloodstream and goes to the
thyroid to tell it to release its
hormone so let's have a look at this
number one tells that one to be released
that jumps into the bloodstream
goes to the thyroid so let's have a look
at the thyroid quickly
the thyroid is endocrine tissue that
hugs the front of your trachea
your windpipe what you'll find is that
the thyroid produces a couple of
important hormones it produces
interestingly t4
well most of it is turned into t3 t3 is
the most active
thyroid hormone so when we talk about
thyroid hormones we're talking about t3
predominantly 80 percent 20 that's the
ratio that we see here
there's another hormone that's released
by the thyroid called calcitonin
calcitonin talk about that in a sec
so thyrotropin releasing hormones
released by the hypothalamus travels
down this blood supply tells the
anterior pituitary to release thyroid
stimulating hormone
that jumps into the bloodstream tells
the thyroid to release t3 and t4
what do they do they play an extremely
important role
and catecholamine release
what's catecholamine catecholamines are
neurotransmitters these are things and
hormones are things like
adrenaline or noradrenaline or
epinephrine norepinephrine for example
that's what thyroid hormones do calcitonin
calcitonin
is interesting what calcitonin does is
it decreases the amount of calcium in
the bloodstream
if there's too much calcium in the
bloodstream calcitonin
drops that calcium down helps us
reabsorb and hold on to that calcium
predominantly in our bony tissue that's
the thyroid hormone
what happens when corticotropin
releasing hormone is released from the
hypothalamus traveling through this
blood supply stimulates
adrenocorticotropic hormone
to be released also known as acth
that jumps into the bloodstream and
travels to adreno
adrenal adrenal gland cortico the
outside of the adrenal gland
tropic is it's telling it to release
another hormone
so it's all in the name let's go to the
the adrenal gland now if we look at the
adrenal gland you've got the cortex
which is the outside of it like the shell
shell
which is the inside they release
different hormones so for example
adrenocorticotropic hormone will go to
the cortex more specifically
aldosterone and androgens
we'll leave androgens out but androgens
which are male sex hormones
so cortisol what does cortisol do cortisol
cortisol
increases blood glucose
and cortisol also stimulates our fight
or flight
response really importantly what does
aldosterone do
aldosterone increases our reabsorption
of salt what does that mean
increases our reabsorption of salt
aldosterone travels
to our kidneys and tells our kidneys
don't pee out that salt or that sodium
keep it in the blood this is important
because wherever sodium goes
water follows so if we reabsorb more
sodium into our bloodstream
water follows and it increases our blood
volume which means it increases our
blood pressure aldosterone helps
increase blood pressure increase
blood volume and also maintain hydration
really important
what about the medulla well the medulla
isn't stimulated
very strongly at all by acth but the
hormones that are released by the inside
of the adrenal gland are predominantly noradrenaline
and adrenaline what are they that's
norepinephrine and epinephrine all right
what else growth hormone okay growth
hormone is released
from the anterior pituitary gland and
that stimulates
growth unsurprisingly growth hormone
increase growth things like
increased protein synthesis
increases growth increases metabolic processes
processes
all right prolactin prolactin lactin lactation
lactation
the production of breast milk
pro-lactation so
prolactin which is released by the
anterior pituitary gland in response to
prolactin releasing hormone from the hypothalamus
hypothalamus
increases milk production
now it's not milk ejection which is let
down through breastfeeding
that's oxytocin which i'm going to talk
about in a second
and then the gonadotropins the
gonadotropins so tropon it's going to
the gonad so for the females the ovaries
for the males the testes and these
hormones go to both
for females goes to the ovaries for
males go to the testes and has their function
function
what is their function all right
luteinizing hormone let's look at
it stimulates progesterone
it also stimulates ovulation
follicle stimulating hormone stimulates
follicle maturation
what's that mean in the female
reproductive cycle
you've got these immature primordial
follicles they ultimately turn into an
oocyte or an egg that gets released so
fsh released by the hypothalamus
well specifically the anterior pituitary
gland stimulates these follicles to start
start
moving through the process to go towards
the release of a mature
egg the actual release of the egg is
luteinizing hormone
so follicle maturation also leads to estrogen
so two really important hormones that
are released here in response to lh
is progesterone and fsh estrogen
what about in the testes let's have a
look for males in the testes
well luteinizing hormone stimulates a
certain type of cells called
latex cells and what they produce is testosterone
testosterone
that's the hormone produced here testosterone
testosterone
what about follicle stimulating hormone
well there's no follicles in males
but what it does is it stimulates a
certain type of cells in the testes
called setoli cells so both ladies and
setoli cells are in the testes
lady produces testosterone so tole
produces something called
androgen binding protein and both of these
these
to promote sperm production so
unsurprisingly the ovaries
luteinizing hormone follicle stimulating
hormone produced hormones here
and what this does is it leads to
so if you're preparing the uterus and
producing sperm
both of these things coming together is
going to support reproduction
that's going through the anterior
hormones what about those are the
posterior pituitary hormones there's
only two you need to know here
and anti
diuretic hormone known as adh
all right firstly hypothalamus doesn't produce
produce
any hormones to travel down to tell them
to be released
it's just a nerve signal in actual fact
the hypothalamus produces these two hormones
hormones
and sends them down and they're simply
stored in the posterior pituitary gland
now what oxytocin does is we know it's
an important hormone for building relationships
relationships
but it also tells smooth muscle to
contract tells the uterus
to contract and tells a smooth muscle in
the breast to contract to eject
in addition to building relationships
both positive and negative it's not that
feel-good hormone
that everyone says anti-diuretic hormone
diuresis means to release
urine to release fluid from the body
it's anti-diuresis so it stops
the release of that fluid so it stops
peeing so
this hormone gets released in times of
dehydration if we need to maintain water
we release this hormone this travels to
the kidneys
and the kidneys hold on to water and we
don't pee it out so it stops urination
it's there to maintain hydration
all right so that's the hypothalamus
pituitary glands we've gone through the
adrenal glands we also and we've gone
through the
sex hormones and the thyroid there's a
hormone or
i should say there's a gland that sits
behind the thyroid
and what the parathyroid gland is it
hormone
and it opposes the activity of calcitonin
calcitonin
so calcitonin decreases calcium
parathyroid hormone increases blood calcium
calcium
so if our calcium too low parathyroid
releases parathyroid hormone
calcium jumps up if calcium is too
high calcitonin's released and it drops
calcium levels
can you see that what's happening here
is the endocrine system maintains
homeostasis maintains function for the body
body
brilliant that's the parathyroid hormone
the kidneys also release some hormones
what renin does is it works in conjunction
conjunction
to aldosterone increases
blood pressure increases
blood volume erythropoietin increases
red blood cell production why would the
kidneys be in control of red blood cell production
production
well because the kidneys need to
maintain itself being fed oxygen because
it's such a hungry tissue
so red blood cell production the
pancreas we can't forget about the pancreas
pancreas
the pancreas is both an endocrine tissue
and an exocrine
exocrine means it produces chemicals
that get released into ducts
these ducts are contained and this is
part of the digestive system so it
releases digestive enzymes
but it also releases hormones two really
important hormones
are insulin and glucagon
and again these are opposing hormones so
insulin drops blood glucose levels when
they're high
drops blood glucose glucagon
increases blood glucose levels
after a meal insulin's released pulls
the glucose into the cells to be used
for energy
if we're not eating and it's been four
to six eight hours and we haven't eaten
glucagon's released
and it releases stored glucose into the
bloodstream and then the cells can use it
it
for energy and so what we've had a look
at here is a
relatively quick run through an overview
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