- THERE'S A SET OF HORMONES
THAT ARE DERIVED
FROM AMINO ACIDS,
AND THESE ARE
THEIR OWN CATEGORY.
AND ACTUALLY, HALF OF THEM
HAVE A MECHANISM THAT'S SIMILAR
TO THE STEROID HORMONES,
AND HALF OF THEM
HAVE A MECHANISM THAT'S SIMILAR
TO THE PEPTIDE HORMONES THAT
WE'RE GOING TO TALK ABOUT NEXT.
SO THEY DON'T HAVE THEIR OWN
INDEPENDENT MECHANISMS
OF ACTION, SO WE'RE NOT
GOING TO TALK ABOUT THOSE.
BUT I DO WANT TO TALK
ABOUT WHICH HORMONES
FALL INTO THIS CATEGORY.
WE HAVE TWO PRIMARY AMINO ACIDS
THAT ARE THE PRECURSORS
THAT GIVE RISE
TO SOME SPECIFIC HORMONES.
ONE OF THEM IS TRYPTOPHAN.
TRYPTOPHAN IS THE ONE
THAT ERRONEOUSLY WE'VE ALL BEEN
TOLD MAKES US FALL ASLEEP
AT THANKSGIVING
AFTER WE EAT TURKEY.
APPARENTLY THIS IS NOT
A TRUE STORY.
BUT TRYPTOPHAN,
IF IT IS MODIFIED,
IT CAN BE USED
TO PRODUCE MELATONIN,
WHICH IS A HORMONE.
NOW, SEROTONIN IS ALSO
PRODUCED FROM TRYPTOPHAN,
BUT SEROTONIN IS
A NEUROTRANSMITTER.
NOW, I'M GOING TO TELL
THE NEXT LITTLE PIECE,
AND THAT PIECE IS GOING TO
SHOW YOU THAT-- YOU KNOW WHAT?
SOMETIMES THE EDGES
AROUND THE DEFINITIONS
OF NEUROTRANSMITTER
VERSUS HORMONE,
SOMETIMES THE EDGES ARE,
LIKE, SUPER BLURRY,
AND IN FACT, LIKE,
REALLY BLURRY.
RIGHT NOW THEY'RE ABOUT TO GET
REALLY BLURRY.
TRYPTOPHAN GIVES RISE
TO MELATONIN.
TYROSINE IS AN AMINO ACID
THAT GIVES RISE TO TWO GROUPS OF
AMINO ACID DERIVATIVE HORMONES,
AND THEY HAVE TWO
DIFFERENT MECHANISMS.
SO ONE OF THE GROUPS ARE--
THE WHOLE GROUP IS
CALLED CATECHOLAMINES.
AND THE CATECHOLAMINES,
HOPEFULLY YOU LOOK AT THESE GUYS
AND YOU'RE LIKE,
"WAIT A MINUTE.
I'VE HEARD OF THOSE GUYS."
DOPAMINE IS ONE OF THEM.
NOW, IF YOU KNOW ANYTHING
ABOUT THESE CHEMICALS,
YOU PROBABLY ARE GOING,
"WAIT A MINUTE.
DOPAMINE?"
DOPAMINE IS A NEUROTRANSMITTER.
AND THEY ACTUALLY ARE REFERRING
TO THESE GUYS AS NEURO HORMONES,
BECAUSE NOREPINEPHRINE
AND EPINEPHRINE ARE
ALSO IN THIS CATEGORY.
BOTH OF THESE, ALL OF THESE,
CAN ACT LIKE HORMONES,
BECAUSE THEY CAN BE
DUMPED INTO THE BLOOD.
ACTUALLY, I DON'T KNOW
IF THAT'S TRUE ABOUT DOPAMINE,
BUT IT IS TRUE ABOUT
NOREPINEPHRINE AND EPINEPHRINE.
IF THEY'RE DUMPED
INTO THE BLOOD,
THEY ACT LIKE HORMONES,
BUT THEY CAN ALSO ACT
LIKE NEUROTRANSMITTERS.
AND IF THEY'RE TRANSMITTED
ACROSS A SYNAPSE
TO A VERY SPECIFIC TARGET,
THEN THEY'RE
CONSIDERED NEUROTRANSMITTERS.
SO TECHNICALLY,
THE CATECHOLAMINES ARE--
I CAN DO THIS.
TECHNICALLY THEY
ARE NEURO HORMONES.
ALL RIGHT.
THEIR MECHANISM OF ACTION IS NOT
THE SAME AS A STEROID HORMONE.
AND YOU COULD ACTUALLY
THINK ABOUT THAT,
AND THAT WOULD BE A PHENOMENAL
ESSAY QUESTION ON AN EXAM.
WHY, IF YOU HAD TO GUESS,
IF YOU HAD TO ARGUE
AND DEFEND YOURSELF,
WHY WOULDN'T
THESE GUYS HAVE THE MECHANISM
OF STEROID HORMONES?
PROBABLY THE FIRST THING
YOU SHOULD THINK OF IS, "DUDE,
STEROID HORMONES ARE SLOW."
AND EPINEPHRINE
AND NOREPINEPHRINE, REMEMBER,
THESE GUYS ARE INVOLVED IN
A SYMPATHETIC NERVOUS RESPONSE.
THIS IS BASICALLY ADRENALINE.
AND IF THEIR ACTION WAS SLOW,
YOU, MY FRIEND,
WOULD BE EATEN BY THE BEAR.
THAT WOULD BE TRAGIC.
SO THAT TELLS YOU RIGHT AWAY
THAT THE MECHANISM
OF THE PEPTIDE HORMONES
THAT WE'RE GOING
TO TALK ABOUT NEXT,
THE MECHANISM IS FASTER
THAN THE MECHANISM
OF THE STEROID HORMONES.
HOWEVER,
ALL OF OUR THYROID HORMONES ARE
ALSO BUILT FROM TYROSINE,
AND ALL OF THEM
HAVE THE MECHANISM
OF THE STEROID HORMONES.
SO A TOTALLY SAME PRECURSOR,
BUT A TOTALLY
DIFFERENT MECHANISM.
PROBABLY A GOOD IDEA
TO REMEMBER BOTH OF
THOSE DIFFERENT CATEGORIES.
NOW, LET'S LOOK
AT OUR PEPTIDE HORMONES,
AND LEARN ABOUT THE MECHANISM
OF ACTION FOR THOSE GUYS,
AND SOME CHARACTERISTICS
THAT THEY HAVE.
AND THEN CONSIDER AGAIN,
WHY IS IT BENEFICIAL
TO HAVE OUR ADRENALINE TYPE
SUBSTANCES ACT IN THAT MANNER?
