have you ever thought about the way the
different parts of our body communicate
you know i think we often consider the
body to be this one complete thing this
this self but really our body is
composed of lots of parts there are lots
of organ systems and each of those has
organs and all of those organs are made
of tissues and all those tissues are
made of cells and it's crazy but there
are a hundred trillion or at least
roughly a hundred trillion cells in our
body
so it's curious then
how do those 100 trillion different
parts communicate
well one way is through the through the
nervous system and through the prelate
tracks of nerves but not every part of
the body is connected by nerves i mean
how for example would part of the brain
go about communicating with part of the
kidney
well to talk about that we're going to
have to talk about the endocrine system
and the endocrine system is a system of
organs that are called glands
and these glands secrete little chemical
messages that are called hormones
and they release those little chemical
messages called hormones into the
bloodstream so that they can circulate
from one part of the body to another
part of the body in order to initiate an
effect
and there are there are many parts of
the body that use these hormones to
communicate but certain organs are
really defined by this method of
communication and we call them endocrine
glands and so one of the major endocrine
glands is the hypothalamus
and the hypothalamus is located right
here
it's a member of the forebrain and as a
member of the the brain it receives a
lot of those signals that we talked
about from the nervous system so those
nerve signals are funneling into the
brain and the hypothalamus then as a as
a kind of dual member of the endocrine
system
funnels those signals into the pituitary
gland and so because it plays that dual
role between the the endocrine system
and the nervous system it often gets
tagged line as the control center of the
endocrine system
in addition to stimulating the pituitary
gland the hypothalamus actually makes
some hormones itself also and so it
makes adh
and oxytocin
and adh is anti-diuretic hormone and
it's a main regulator of our fluid
volume in our body and then oxytocin is
a hormone that stimulates the uterus to
contract for females during pregnancy
and so that's that that's the
hypothalamus member of the brain and
member of the endocrine system where it
all begins the control center and then
right below the hypothalamus is the
pituitary gland
the pituitary gland is located right
here dangling right below and so the
hypothalamus is about the size of a
grape
and the pituitary gland is actually
about the size of a green pea but this
little green pea is so important that it
it's called the master gland
and it's called the master gland because
the pituitary gland takes that
stimulation from the hypothalamus and it
directs it to all of the other endocrine
glands or at least almost all of the
other endocrine glands such that their
function is ultimately dependent on the
pituitary gland to work well and so that
little green pea is a really important
part of the endocrine system and so one
of the endocrine glands that the
pituitary directs is the thyroid gland
and the thyroid gland is located right
here in your neck it wraps around your
trachea and your trachea is your
windpipe and so you can feel this
thyroid gland on your neck as you
swallow if you hold your hands right
around your adam's apple and swallow
that meaty thing moving up and down
that's your thyroid gland
and one of its main jobs is regulating
your body's metabolism
and it does that through the thyroid
hormones t3 and t4
and another name for t3 is
triiodothyronine and another name for t4
is thyroxine but the thyroid uses these
hormones the thyroid hormones to
stimulate the body's metabolism which is
crucial because that's how our body gets
energy and then right behind the thyroid
gland are four spots
known collectively as the parathyroid
and the main role of the parathyroid is
regulating our our body's blood calcium
level
and the level of calcium in our blood is
hugely important because calcium does a
lot of stuff in our bodies it's involved
in muscle contraction it's involved in
bone growth and all of those functions
are really sensitive to the level of
calcium that's that's floating around in
our blood and so the parathyroid glands
those four spots on the back side of our
thyroid regulate calcium through the
hormone parathyroid hormone or pth
and then moving down the the torso we
have the adrenal glands
and the adrenal glands are located right
on top of the kidneys here
and they're called the adrenal glands
because they're adjacent to or right
next to the kidney system which is
called the the renal system in in
medical speak
but we really need to further divide the
adrenal glands into two parts the outer
part and the inner part so the outer
part is the cortex
and the inner part is the metalla
and the reason for the distinction is
that the inside and the outside of the
adrenal glands have two different
functions and so we'll start with the
outside or the cortex
and that's where the steroids the
adrenal corticosteroids are made and two
major examples of steroids made in the
adrenal cortex are cortisol
and aldosterone
and cortisol is one of the body's stress
hormones so it functions to increase
blood sugar in times of stress so we
have energy
and it also has some anti-inflammatory
functioning and then aldosterone is one
of the major regulating hormones of our
body's blood volume and how much fluid
is in our veins and arteries and so
that's the cortex and then the metal
that makes a class of hormones called
catecholamines
and two major examples of catecholamines
are epinephrine and norepinephrine and
i'm going to shorten those as epi and
norepi
and sometimes epinephrine is called
adrenaline and and that might be a
little bit more familiar to you but
these catecholamines are really involved
in our body's uh fight or flight
response that adrenaline response that
we have
to uh to a stressful or scary situation
and so the metal and the cortex make up
the adrenal glands but moving down the
list and down the body we have the
gonads
and in females those are the ovaries
and in males the testes
and the gonads release this sex hormones
and so in males the testes produce
testosterone and in females the ovaries
produce estrogen and progesterone but
these sex hormones are mainly involved
in the development of our secondary sex
characteristics like
pubic hair and and
larger frames and males and and breasts
and women but they're also involved in
progressing us through those life stages
that accompany those sex characteristics
like puberty and menopause and then last
but not least we have the pancreas
and it's located right here in the upper
part of the abdomen
and i saved the pancreas for last
because it isn't involved as directly
with the pituitary glands as the other
endocrine hormones were but it still
uses those hormones to stimulate an
effect in a different part of the body
and the effect that the pancreas
stimulates is control over the blood
sugar
and it does that through the hormones
insulin and glucagon
and the pancreas is vitally important
because without its hormones insulin and
glucagon we can't regulate how much
sugar is in the body's blood versus
cells and that can lead to major
diseases like diabetes and so with the
pancreas we can conclude our list of
major endocrine glands and so as we look
at these glands and at these hormones
and we think about all of the different
effects that are being stimulated in our
body by them it becomes pretty clear
that there aren't just a few of these
circulating in our bloodstream there are
literally loads of hormones circulating
through our vasculature at any given
moment and so that kind of that poses a
potential problem if say that you're in
the brain and you're trying to
to tell something to the kidney you're
trying to send him a message and you put
that in the bloodstream and you just
float it down to him how do you know
that it's gonna get there i mean isn't
that what every other endocrine gland is
trying to do
well it turns out that hormones are a
lot like radio waves
in your city or in your town there are
many different radio stations and there
are many different songs being played at
any given time by those radio stations
and
and even maybe from the next town over
there are radio waves filling the era of
your town but unless you're tuned in
specifically to that station you're not
going to pick up on the song that's
being transmitted and in a very similar
way a hormone is not going to be
received unless there's a very specific
receptor on the target cell
and so the receptor and its location are
very important in determining the
hormone function and we have classes
that we use to help us identify which
hormones fall into which function and so
the first class are autocrine hormones
and autocrine hormones function at the
cell that makes them
an example of this is the t cell and the
immune system it actually secretes a
hormone that it makes called an
interleukin that signals the cell itself
to increase its effectiveness in its
immune function and then another class
of hormones are paracrine hormones
and paracrine hormones function
regionally
and an example of that might be the
hormones released by the hypothalamus
that direct the pituitary gland and then
last but not least kind of the classic
class of hormones are the endocrine
hormones
and these are the hormones that function
at a distance
an example of this might be the
pituitary gland stimulating the gonads
way far away and so we have autocrine
paracrine and endocrine classes that
help us determine how hormone functions
and so i know i just told you a whole
lot about hormones but this is your
introduction into one of the most
important ways that the hundred trillion
little tiny individual parts of your
body communicate