this is a forward view of a transparent man

or a semitransparent man,

and this is a posterior, or back view

of a semitransparent woman.

But what these organs that are depicted,

these organs secrete molecules into the bloodstream,

and an organ that secretes things,

these are called glands,

and they secrete these molecules into the blood stream

that regulate other parts of the body,

things that might be quite far away from the organs,

the glands that actually do the secretion.

And so these molecules

that regulate other parts of the body,

these are called hormones.

And the word hormone comes from Greek hormōn,

which means to set in motion,

so one way to think about it, these are molecules

that set things in motion in other parts of the body,

and this is really to regulate the body function.

Now this entire system of glands is referred to

as the endocrine system, endo- referring to fact that

it's acting within the body, -crine originally comes

from Greek word to sift or to differentiate something

and it's a system of organs

or I guess you could say glands

that are secreting molecules,

these hormones into the bloodstream to regulate the body.

I'm not going to go in-depth

in all of these endocrine glands

but just to give you an appreciation of what they do

and what these hormones are all about,

we could list some of the more common ones

that you might hear about.

So for example, the thyroid gland produces thyroid hormone.

This is a version of thyroid hormone.

You see your carbons in the dark gray,

your hydrogens in the white.

You see your oxygens in the red, nitrogen in blue,

and these big atoms right over here, these are iodine,

and thyroid hormone plays an important role

in your metabolism.

In fact, if you have too much thyroid hormone,

that's a disorder called hyperthyroidism,

which would make your metabolism overactive.

Likewise, if you have too little thyroid hormone,

that's a disorder known as hypothyroidism,

in which case your metabolism isn't active enough.

You have hormones like adrenaline

that are released by the adrenal glands,

and that's where it gets the word adrenaline from.

It's often known as epinephrine,

and adrenaline, you might hear things like,

"Hey, so and so is an adrenaline junkie,"

which means they really like a thrill,

and adrenaline actually does play a role there.

It's involved in the fight-or-flight response,

where it'll increase your heart rate

and increase blood flow to the muscles.

And what's really interesting about all of these hormones

is they have so many impacts on the body

because they're released into the bloodstream

and to different cells they might do different things.

This right over here is a variation of estrogen,

which is produced primarily in females in the ovaries,

but it also exists in a male body

and it's associated with a lot of female bodily function,

but once again, not strictly female.

Estrogen also exists in males.

Similarly, you have testosterone,

which is associated with male function

but it also exists in females,

and it's primarily produced in men in the testes.

Thus the name testosterone,

but it can also be produced by the adrenal glands.

And women, it can be produced by the ovaries.

But you could also have a molecule like insulin

which you can see is much larger than the other hormones

that we have looked at.

It's produced in the pancreas

and it plays a super-important role

in how we process sugars and how we store fat

and scientists are constantly discovering new roles

for these various hormones.

Insulin in particular you might associate with diabetes.

People with Type 1 diabetes aren't able to produce

enough insulin to take the sugar out of their blood stream,

to have the cells absorb the sugar.

Insulin will bind to the surface of a cell

so that it will start taking in sugar

from the blood stream.

People with Type 2 diabetes, they have an insensitivity

to insulin, so they might have to take extra insulin

in order for their cells to take in the proper amount

of sugar.

But the big idea here is that the endocrine system,

although it might not be as obvious,

or it might not be as well known

as something like say the nervous system,

it plays a pivotal role in your body.

It helps regulate your body.

It helps keep it at the right temperature,

the right blood pressure,

your heart pumping at the right rate.

One way to think about this is

the notion of homeostasis, which is

derived from similar and staying the same.

So keeping your body at the right temperature

regardless of what the temperature is outside

or regardless of what your body is doing,

there's a whole series of roles that these hormones,

which are released by these endocrine glands

actually do.