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- [Voiceover] The
endocrine system has glands

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scattered throughout the body.

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Alright, so let's look
at the endocrine system

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of what it really is.

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Basically, just a collection
of specialized cells.

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All of these specialized
cells are secreting hormones.

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And these hormones, are being secreted

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primarily into the blood.

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They're called ductless glands.

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So secreting into the blood,

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sometimes into the fluid around cells,

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that's called interstitial fluid,

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or sometimes the lymph.

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Think of that as part
of your immune system.

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Hormones themselves,

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well you've probably
heard of a couple of them.

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Might have heard of growth hormone,

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thyroid hormone.

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So there's many different
types of hormones,

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but hormones in general

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are just chemical messengers.

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They're chemical messengers,

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that circulate throughout the bloodstream,

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and act on a specific cell in the body.

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Each hormone has certain target cells.

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So here's the basic idea of what the

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endocrine system is.

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We'll go through the major
endocrine glands first,

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and then at the end

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we'll pick up a few of
the more minor ones.

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First off, pituitary gland.

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Now pituitary is broken up
into anterior and posterior.

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Well, anterior is front,
posterior is back,

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but contains hormones
like in the anterior side,

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adremocortotropic hormone,

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thyroid-stimulating hormone,

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follicle-stimulating,

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lutenizing hormone,

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prolactin,

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and growth hormone.

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While the posterior side of the pituitary,

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is the storing,

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the antidiuretic hormone,

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storing oxytocin.

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The hypothalamus is found just above

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the pituitary gland.

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The hypothalamus,

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has a whole bunch of releasing,

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or inhibiting hormones.

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So pretty much,

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the hypothalamus,

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will send a hormone to
tell the pituitary gland

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to release something,

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or to inhibit it,

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to prevent release.

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Pineal gland,

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a little bit further back in the brain,

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produces melatonin.

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Well melatonin is kinda
like a sleep wake cycle.

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The thyroid gland,

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produces thyroxine,

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calcitonin here.

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Parathyroid?

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Well it's just little tiny dots,

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on each side of the thyroid gland.

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That's your parathyroid hormone, there.

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The thymus,

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is found just above and
in front of the heart.

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Tymopoietin, thymosin are two examples.

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Now the adrenal glands,

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are like two separate glands in one.

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You have the cortex,

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which is the outside,

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and you have medulla,

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which is the inside.

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So the adrenal gland cortex,

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produces things like
cortisol, aldosterone,

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just a couple of examples.

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The medulla, which is the inside,

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produces norepinephrine,

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and epinephrine.

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Now in the case of epinephrine,

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think of adrenaline.

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Same basic idea.

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You may have heard of an epipen before,

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that's epinephrine.

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Its meant to really get that body going.

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Pancreas.

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Glucagon, insulin, dealing
with sugar regulation

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in the blood.

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And the gonads.

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Obviously male versus female specific.

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Female ovaries, estrogen, progesterone.

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Male testes, testosterone.

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Now those are going to be
the major endocrine glands.

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But here are a few other glands that also

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are going to be having
endocrine functionality.

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The heart.

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You think of it as
cardiovascular, pumping blood,

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but it actually has a hormone.

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Stomach, you think of it holding food,

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also contains a hormone.

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Intestines, again,

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also secretes hormones.

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The kidneys.

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Usually kidneys are filtering your blood,

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creating urine.

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They're also creating hormones.

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So there's really quite a few
different glands in the body

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that create hormones.

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Now these hormones,

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because they're in the blood,

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have access to every
single cell in the body.

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Once you put the hormone in the blood,

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it's travelling from head,

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all the way down to foot.

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But the key thing is,

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the hormone only acts

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on it's own target cell.

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So there might only be target cells

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in one organ in the entire body.

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That means the rest of the body,

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the hormone just keeps on
traveling right through.

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Doesn't even stop.

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Now only very specific cells

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have receptors for specific hormones.

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So for instance,

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thyroid-stimulating hormone.

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Just from the name you'd probably guess

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that it's going to stimulate the thyroid,

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and that's right.

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That means the receptors for
thyroid-stimulating hormone

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are only on the thyroid gland.

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But yet you can find

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thyroid-stimulating hormone,

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in the blood of your hands,

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the blood down your feet,

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because the hormone goes everywhere.

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It can only act at the proper receptor.

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Now we have two different
control mechanisms listed here.

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Endocrine and nervous.

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Nervous by far is the faster response,

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but endocrine, even though it's slower,

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it can be pretty quick, though.

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Think about how fast after a
very threatening situation,

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life threatening situation,

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you feel that rush of adrenaline.

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Well that's caused by
a hormone, epinephrine.

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So it can be pretty quick sometimes,

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but still slower than nervous.

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And both these inner systems,

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interact though.

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Both endocrine and nervous

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have to communicate,

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have to work together,

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to make sure your body
maintains homeostasis.

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Now homeostasis is just a proper balance.

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So to keep your body healthy and happy,

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both the endocrine and nervous systems

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must talk,

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must work together,

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and must keep a constant interaction.