Types of hormones | Endocrine system physiology | NCLEX-RN | Khan Academy

Types of hormones | Endocrine system physiology | NCLEX-RN | Khan Academy

OK. So when I introduced
the endocrine system, I mentioned that hormones
can be classified by where they function. And we talked about autocrine
function and paracrine function and endocrine function. But maybe even more
importantly, hormones can also be classified
by structure. And I say more importantly
because the structure of a hormone really
determines how it works. And so that’s what I
want to talk about today, the three major
types of hormones. And the first major
type of hormones are proteins and polypeptides. And just as a refresher,
proteins and polypeptides are made up of amino acids. And these amino acids are linked
together with peptide bonds. And so many peptide
bonds come together to form a polypeptide
or a protein. And these proteins
and polypeptides form most of our
body’s hormones. And these hormones can
range from small to large. And to give you an example
of what I mean by that, imagine it’s three or so
amino acids linked together forming a hormone. That would be a
small polypeptide. In three amino
acids, we’re talking about a handful of atoms,
maybe 20 or so atoms. And just as a
frame of reference, a cell in your
body, one cell, has on the order of a trillion
atoms just inside that one cell. And there are 100 trillion
cells in your body. And so we’re talking about
very, very, very small things. And they can range from
these small collections of amino acids, all
the way to hundreds and hundreds of amino acids. So they can get quite large. And the break point
becomes right around 100. And that’s where we
shift from calling them polypeptides to proteins. And just like all
proteins in your body that are going to be excreted,
proteins and polypeptides hormones are made in the
rough endoplasmic reticulum of the cell. And I’ll shorten that to “RER.” And they go from the rough
endoplasmic reticulum to the Golgi apparatus. And from the Golgi
apparatus, they’re kind of repackaged into
vesicles that can eventually be excreted from the cell. And because proteins
and polypeptides are made of amino acids,
they’re typically charged. Which makes them water
soluble, but it also gives them a really hard
time crossing cell membranes. And so typically
the receptors are located in or on a cell surface. And because the receptors are
located in or on a cell surface and these protein and
polypeptide hormones can’t actually travel into
the cell, what they do is they initiate
a cascade effect of secondary messengers
inside the cell. And I’m going to
do an entire video about how that
signaling cascade using secondary messengers
actually works. But the main idea is that when
these protein and polypeptide hormones bind to
the cell surface, they initiate a response
inside the cell. And we refer to that as a
secondary messenger system. And so to save some
time, I went ahead and drew in an example
of a polypeptide hormone. And I’m going to kind
of fade it in for us. And I want to show
you on this drawing where the peptide bonds are
because these peptide bonds really pull this class
together and unify them. And so right in between
the carbon and the nitrogen here and the carbon
and the nitrogen here, I’ll draw some arrows. These are the peptide bonds
that I was referring too, these carbon-nitrogen bonds. And so they can be small
and they can be large. But these links of
amino acids that are used as chemical messengers
to signal effects in the body are called proteins
and polypeptides. And one example is insulin. Insulin is a relatively
large hormone. And it’s a protein hormone. OK. So we’ve got proteins
and polypeptides. And then the second major
type of hormones are steroids. And when we hear
steroids, I don’t know, the first thought
that comes to my mind are a bunch of athletes
getting in trouble with their regulating
committees. But steroids are actually one
of the major types of hormones used in our body to communicate. And so there are a lot
of steroids in our body. But steroids come from lipids. And the major lipid that
these steroids come from is cholesterol. And because they come
from cholesterol, steroids have a really
characteristic structure that all of them share. And so I went ahead and
I predrew that as well. I’m going to fade that in. And so this is kind of
the characteristic steroid backbone. And so you can see there are
four ring structures here. And these rings are
made of carbon atoms. And so there are three
cyclohexane rings or six-membered carbon rings
and one cyclopentane ring. And I’m going to label
those A, B, C, and D. And what this
characteristic structure, comes a really characteristic
way of signaling a cell. And so unlike proteins and
polypeptides, whose receptors are on the cell
surface, steroids, because they’re made of
lipids, have a really easy time passing through
the cell membrane. And their receptors are
located inside the cell. And so steroids usually
go all the way inside of the cell to signal the
receptor as primary messengers. They’re actually
doing the signaling. And oftentime,
their receptors are located either in the cytoplasm
or all the way in the nucleus. But steroids typically
go in, and their effect goes all the way down to the
transcription and translation level of proteins. And so as primary messengers,
they’re going inside the cell, and they’re effecting a
change in that cell that’s going to result in
the transcription and the translation
of new proteins and new products
inside the cell. And I’m going to do a video
on how these steroids actually affect the cell as well. But for now, I want
you to be thinking of steroids as one of the major
hormones that are in our body, not just a means
for athletes getting an edge on the competition. And so some examples of
big steroids in the body are those that come
from the adrenal cortex, like cortisol and aldosterone,
and those hormones that come from the gonads, like
the sex hormones, testosterone and estrogen and progesterone. And so we’ve got steroids. And we’ve got proteins
and polypeptides. And the third major type
of hormones by structure are tyrosine derivatives. And tyrosine derivatives come
from the amino acid tyrosine. And you might have
caught on that I said these come from tyrosine,
which is an amino acid. And I told you earlier that
protein and polypeptide hormones are made
of amino acids. And so you might
ask yourself, why do these get their own major
class if these are also made of an amino acid? And what makes them
really special, A, is that they’re made
up of one amino acid. So one amino acid,
tyrosine, is manipulated to make these hormones. And B, these hormones that
are derived from tyrosine end up being able
to sometimes act like proteins and
polypeptides and sometimes act like steroids. So they really get
their own class. And an example of tyrosine
derivatives in the body are those that come from the
thyroid gland, like T3 and T4, or triiodothyronine
and thyroxine, that stimulate metabolism. And these tyrosine derivatives
act really similarly to steroids. And then another example
of tyrosine derivatives are catecholamines. And catecholamines
are those hormones that are produced in
the adrenal medulla that are involved in our fight
or flight responses, like epinephrine
and norepinephrine. And these thyrosine derivatives
act really similarly to peptides by binding on
the outside of the cell and releasing those secondary
messengers inside the cell. And so the thyroid hormones
that are tyrosine derivatives act like steroids. And the catecholamine
tyrosine derivatives act like proteins
and polypeptides. But it’s important
to remember that they form their own unique
class because they’re all derived from the
amino acid tyrosine. And because I did
it for proteins, and polypeptides, and
steroids, I went ahead and I drew in what
tyrosine looks like. So that’s tyrosine. And that’s the amino acid
that this class of hormones is derived from. And so I know it’s
hard to make learning these types of hormones fun. But maybe at least we
can let our minds blow up a little bit over the
fact that the structure of these hormones dictates
almost everything we think or do, from fear, to hunger, to
urinating, and pushing babies out. All of our responses
to the world around us are signaled by hormones.

26 Replies to “Types of hormones | Endocrine system physiology | NCLEX-RN | Khan Academy”

  1. ALL THESE LECTURES ARE MISS LEADING; IN THAT NON OF THEM ADDRESS ELECTRICAL OR CHEMICAL COMMUNICATION AND the optimal condition which allows these communications to take place.  That would be called conductivity and only Salt with trace minerals permit this.

  2. prolly a slip of tongue but nevertheless thot i wud point out n correct:  steroids are NOT made of lipids, most steroids are hydrophobic and as a result they r classified as lipids…

  3.  @Harsh Bhavsar actually, to correct you, hydrophobic molecules are lipids! and, steroids are made of lipids! now, steroids can possess an OH grouping.which makes it partly hydrophilic  but "none the less"  ALL STEROIDS ARE HYDROPHOBIC IN WATER DUE TO THEIR CH3 BONDS! 

  4. I'm a med student and I really appreciate these videos. Although my assignments are up to 300 pages long, this make things simple enough to understand the concepts before I do my assignments.. Thanks Khan-academy!

  5. Very nice video . When u were talking about tyrosine derivatives. You said they can work as protein being an amino acid but how it can work as steroid. Can you plz elaborate. The rest of the video is superb

  6. My book has it classified as proteins, steroids and biogenic amines. So I'm assuming tyrosine derivatives fall under biogenic amines?

  7. Hello KhanAcademy! thank you so much for all of your videos I have learned a lot! and I just Passed my NCLEX yesterday! thank you so much! 😘

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