The Adrenal medulla, composed of neural tissue, functions as a crucial component of the sympathetic nervous system, releasing epinephrine and norepinephrine in response to acute stress to initiate the "fight or flight" response.
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all right Niner in this video we're
going to talk about the adrenal gland if
you guys haven't already seen it go into
our uh Endocrinology playlist and watch
all of the videos up until this point
first one was on the zone of glosa
second one was on the zone of facula
third one was on the zone of reticularis
in this video we're going to
specifically be focusing in on the
Adrenal medulla okay so Adrenal medulla
is this inner part right and it's
actually made up of neural tissue
because if you see we're zooming in on
it cuz what's this part right here again
Adrenal
medulla okay so what I'm doing is I'm
zooming in onto the Adrenal medulla and
I'm looking at specifically one neuron
because you know that this this actual
Adrenal medulla is made up of neural
tissue specifically they call these uh
cells here these neurons they call them
okay now these chromin cells are
basically going to be cell bodies of the
postganglionic motor neurons of the
sympathetic nervous system let me say
that one more time these chromin cells
are going to be the
postganglionic motor neurons of the
sympathetic nervous system and I'll
explain what I mean by that all right so
in order for us to do this we have to
start here in the actual cross-section
of the spinal cord in the cross-section
of the spinal cord about from thoracic
one to
L2 is your sympathetic component or
portion of the spinal cord okay from T1
lumbar outflow or
output okay this right here is where
you're simp sympathetic nervous system
is actually going to be coming out of
the spinal cord now the only time the
Adrenal medulla is really stimulated is
during shortterm stress okay so
stressful situations in other words
fight or flight okay so what is the
primary stimulus of this the primary
stimulus of the sympathetic nervous
system is when there is usually a short
term or another term we could use here is
is acute
acute
stress okay
or anything that's going to try to
trigger our sympathetic nervous system
so you if you like to think about it
like this
fight or flight
right so for example if I were to give
you an example in this let's say that
I'm getting chased by an orangutang okay
little vicious little suckers okay that
sucker is chasing after me okay I'm
going to want to activate my sympathetic
nervous system so that I can do a whole
bunch of different types of
physiological functions so that I can
can run away from that little guy okay
how am I doing that well one way that
our sympathetic nervous system is
activated is through our hypothalamus
you know hypothalamus is actually a very strong
strong
regulator okay because he has a
sympathetic and a
parasympathetic component so he actually
can send down fibers he can actually
send descending fibers down
to the spinal cord where in T1 to L2 so
let's say that there's some type of
short-term acute stress or some type of
fight ORF flight situation right where
you need to be able to run away from
that little orangutang and this
hypothalamus sends down these pratic
potentials all the way down to about T1
to L2 which is the thoraco lumbar
outflow right specifically right in this
area you see this area I'm going to kind
of like dot around it you see that area
right there this component that
gray
Horn of the spinal
cord okay and in the lateral gray Horn
of the spinal cord you see these little
orange like structures there these
little orange like structures are the
cell bodies of the preganglionic motor
neurons okay again one more time these
orange structures right there are the
cell bodies of the preganglionic motor
neurons of the sympath itic nervous
system so what happens is usually if I
were to follow this thing out here
usually what happens
is let's say that I have the axons
coming out here all these
axons okay all the axons are coming out
and they're moving through you know this
actual ventro Ramis and then eventually
they go into a chain ganglia right so
they go into a sympathetic chain ganglia
however these ones are different they
don't go to a chang gangle they actually
move right through the Chang ganglia and
they come to
the Adrenal medulla and in the Adrenal
medulla guess what I called these again
the chromin cells were the specifically
they were the cell bodies of the
postganglionic motor neurons of the
sympathetic nervous system now again one
more time why am I explaining this
because uh normally for the sympathetic
nervous system the preganglionic motor
neurons are very short and they have to
go to a chang ganglia right and then
they'll get taken to their target organ
because then their postganglionic motor
neurons are long this time it's opposite
for the adrenal Med it's an exception
where the preganglionic motor neurons
are very long they pass through the
ganglia the chain ganglia and they go
out to the cell bodies which are inside
of the actual organ so this is an
example of what's called an intramural
gangon okay so again what would this be
an example of this is an example of one
of the exceptions called a intra
intra mural
mural
ganglion one of the exceptions of the
sympathetic nervous system okay now that
we've cleared that up now let's go ahead
and get into all these
mechanisms so what's going to happen
what what kind of fibers are these these
purple fibers these purple fibers are
actually called colonic they're Cola
Cola
nergic meaning that they release
acetylcholine so they're going to start
releasing acetylcholine and
acetylcholine is going to start binding
onto this receptor here in this chromen
cell which could be on it could be on
the cell body or it could be on the
dendrites but once it binds onto the
cell certain ions start flowing in right
so you're going to have cations like
sodium flowing in here and when it flows
in what happens it could activate
specific Action potentials which could
stimulate certain processes within the
cell look what happens as a result of
these sodium ions coming in and what
kind of receptor would this be this
receptor here is actually called a nicotinic
receptor now once there's this action
potential and it places a charge on the
membrane it might activate specific
enzymes so certain enzymes might get
activated by this uh
depolarization and then look what
happens it might activate specific
Pathways that help to trigger a specific
biochemical pathway because you know we
have to make specific chemicals in this
area look what happens okay so who's
going to be the first guy that we start
off with up here okay it's it's going to be
be
tyrosine so tyrosine is the guy that we
start with he's an amino acid he's the
building block for these processes but
then we can take these Tyro
tyrosines and we can lead to this
tyrosine we can actually cause it to be
converted into El
Doopa okay and then elopa is converted into
into
dopamine and then dopamine is converted into
into
norepinephrine and then norepinephrine
is converted into epinephrine so you
know what actually this guy is secreting
it's secreting a lot of different
secreting two main chemicals out here
two main chemicals from these synaptic
vesicles one is going to be
epinephrine okay the other one's going
to be noro epinephrine but out of these
two that are being secreted or released
out of the synapse into the bloodstream
80% of it is going to be epinephrine and
20 % of it is going to be neuro
epinephrine all right so you know in
order for this Pathway to occur there's
multiple enzymes involved in each of
these steps I'm just going to mention
them for you um again you could actually
have tyrosine to L Doopa this could be
through What's called the tyrosine
hydroxy enzyme I'm just going to
abbreviate it for you l dopa to dopamine
this is actually dependent upon dopa D
carboxilate so it stimulates this step
dopamine to norepinephrine is actually
through dopamine beta
hydroxylase and then then this
norepinephrine this one's a heck of a
name it's called pheny ethanolamine in methyl
methyl
transferase and it stimulates this step
okay so all of these enzymes are helping
this whole Pathway to occur whenever
this is providing a
stimulus this whole pathway can occur
and and actually enhance this process
here now normally epinephrine and
norepinephrine they can actually be
presynthesized and form here in these
vesicles and technically what can happen
is whenever there is this sodium rushing
in it helps to be able to reach
threshold for this axon and then what
happens is action potentials are
actually going to be produced down this
axon once it's produced down this axon
these Action
potentials it gets down to this actual
terminal bulb and what happens is when
it gets down to this terminal bulb you
know down in the terminal axon bulb here
there's actually calcium channels and
once you hit about positive 30 molts
these calcium channels open and calcium
starts flowing in here and then what
does calcium do it acts as the bridge
between these little called synaptop
protein synapt breven and syta taxin it
actually causes these vessicles with the
cell membrane to merge and whenever it
merges guess what
happens we release out
into the synapse which is actually going
to go into the bloodstream we're going
to release out the norepinephrine
and epinephrine these are the two
chemicals that we're releasing into the
bloodstream so again let's do a quick recap
recap
the colonic neurons are going to be the
neurons specifically from the
preganglionic sympathetic so these are
preganglionic sympathetic motor neurons
they're releasing acetylcholine onto
these chromin cells which are in the
Adrenal medulla which are acting like
the sympathetic postganglionic motor Nur
right so this is an example of an
intramural gangon then so once this
acetylcholine binds onto this receptor
this nicotinic receptor it allows for
sodium to flow in right triggers like
it's called a graded potential once it
causes that graded potential it brings
the resting membrane potential closer to
threshold right once it hits threshold
here in the axon hilic it triggers these
Action potentials that start moving down
the axon and then when it moves down the
axon what happens calcium ions flow into
the axon terminal bulb and lead to the
exocytosis of norepinephrine and
epinephrine now this whole pathway can
actually be enhanced based upon certain
stimuli but usually epinephrine neopine
phrine are pre-formed they're already
synthesized and they're sitting down
here in these vesicles waiting for these
Action potentials to occur and again if
you want to remember this it's tyrosine
to elopa Via the tyrosine hydroxylase
lopa to dopamine via the dopa
decarboxylase dopamine to norepinephrine
via the dopamine beta hydroxylase and
then norepinephrine to epinephrine via
the pheno ethanolamine in methyl
transferase out of most of these enzymes
this is probably the more important one
because he's helping to convert Norm
epinephrine to epinephrine so in these
cells here more of this enzyme is
expressed so that you can have more
epinephrine via 80% versus 20%
norepinephrine okay so now we've done
that okay how is this epinephrine and
this norepinephrine that we release can
to help us to run away from this
orangutang all right let's see you know
our actual muscles and our brain and a
lot of our body actually depends upon
glucose so usually when we're in a
certain type of stressful situation our
sympathetic nervous system wants to get
as much nutrients into the bloodstream
as it possibly can so look what it does
here let's say we fall this epinephrine
onto this liver and it comes onto the
liver and what it does is it stimulates
a specific adrenergic receptor here once
it stimulates this adrenergic receptor
look what it does it activates specific
uh G protein pathway you already know
this G stimulatory and then normally
it's bound to GDP which keeps it off if
it's bound to GTP it turns it on then
what happens it helps to go over and
activate a specific type of affector
enzyme this affector enzyme which
actually embedded into the cell membrane
is going to do what's its name his name
is AD denate cyclas he converts ATP into
cyclicamp and then cyclicamp actually is
going to activate protein kyes
a how is this significant well let's
see you know there's a big storage
molecule inside of our liver about 300
gr of it is actually still worthin a
liver look at this guy here I'm going to
give you it's a string of glucose
molecules a polymer of glucose molecules
if you guys have already watched the zop
ficula video you already know what's
going to happen here but this is called
glycogen right this is called glycogen
so this molecule here is a polymer of
glucose and he is called
glycogen now what happens is there's
certain types of enzymes that are
involved in this process particularly G
glycogen phosphor and debranching enzymes
enzymes
but look what it does I can start
cutting this
glycogen and converting it into a whole bunch
bunch
of individual monomers what are these
individual monomers here called these
individual monomers here are called
glucose oh I love it so what happened
glycogen went to glucose what is this
process called whenever you go from
glycogen to glucose this process here
and a hole is
genalysis right and if you guys remember
from the zop ficula video who was
helping to be able to increase the
sensitivity of those receptors cortisol
right so if you remember cortisol was
actually helping to remember if you
remember cortisol was that little purple
molecule here's our
cortisol just a tiny little correlation
it helped to increase the sensitivity of
these receptors because you know
cortisol on its own actually does the
reverse pathway glycogenesis
okay now what else can this liver do
this beautiful liver look what else it
can do it can
take amino acids so let's say that we
have amino acids here okay it can take amino
amino
acids it can take
glycerol and I'll show you where that
glycerol comes from it can take lactic
acid and it can take odd
chain fatty acids and look what it can
do to it it can take all of these things
and convert all of these things
things into
into
glucose that's wild right guys so what's
the overall result of these guys they
get converted into glucose so you're
going to make more glucose so what is
this right here called again these are
odd chain fatty acids glycerol amino
acids lactic acid they can get converted into
into
glucose what is this process called as a whole
whole
it's called glucon neo genesis so what
is it called gluco
gluco
neo genesis what's the overall result
what are we putting into the blood
what's going to get put into the blood
so let's say that there's a circulation
here right so let's say I actually draw
a small little vessel here here's a small
small
vessel and this glucose gets put into
the bloodstream what happens to the
glucose levels within the blood it
increases so we have increasing blood
glucose levels what is that called when
you have increasing blood glucose levels
hyperglycemia why is that
relevant to the sympathetic nervous
system because you know your skeletal
muscles can use that glucose to start
helping to contract and run away from
that crazy little orangutang right
that's one reason okay so that's one
pathway so far let's see what it does on
our fat tissue okay it comes over here
and acts on the fat tissue so let's
let's show this because again
norepinephrine is also going in this
pathway but but again more of it is
actually going to be epinephrine so then
epinephrine comes over
here and it binds onto this G protein
coupled receptor and you guys already
know this we have already talked about
this what enzyme does he activate you
guys remember that little
scissors he activates a specific Cutters
and these cutting enzymes help to be
able to cut up the
triglycerides what were these enzymes
called do you guys remember they were called
called
hormone sensitive lipase so this called
hormone sensitive lipase hormone
sensitive lipas hormone sensitive lipase
he stimulates these enzymes if these
enzymes are stimulated what are they
going to start doing they're going to
start cutting up and going Chop sooy on
these triglycerides and what is it going
to break out what's going to come out of
it out of this is actually going to come
what glycerol so glycerol is actually
going to be one component this is
actually going to be that glycerol that
head of the triglyceride right what was
the other component that's going to be
coming out of
this fatty
acids and what were the fatty acids
represented as they were represented as
these fatty acid Tails right they're
represented as these little Tails could
be like pil COA right or pic acid which
can get converted into P COA in your
liver but this glycerol where was it
going you can utilize it there so this
glycerol can go to the liver and it can
be utilized
look look what happens to this glycerol
he can actually
be utilized in this pathway of
gluconeogenesis beautiful all right what
about these fatty acids these fatty
acids could go to the muscle and they
could actually come to the muscle and if
they're utilized by the muscle what's
the muscle going to use these fatty acids
acids
for they're going to use it to break it
down right baa oxidation and then what's
the overall results of that what's the
muscles going to produce as a result a
lot of ATP what is ATP in important for
within the muscles contraction to allow
for that cross Bridge right so it helps
with contraction of the muscle why
because I got to start you know cranking
out some I got to start running or I
might have to you know fight the
orangutang you know to be able to
protect myself right so it's activating
spec specific types of fatty acid
oxidation to increase the ATP so that I
can have to fight off that little crazy
arit thing Okay so we've increased of
our glucose levels we've caused fatty
acid us to be utilized by the muscles
and we've used glycerone gluconeogenesis
what else can to do you know our heart's
responsible for being able to pump blood
right and we need our blood pressure to
go high you ever notice when you're
really really stressed or you have a
fight or flight attack what happens to
your heart it's pumping like crazy right
why because epinephrine and or
epinephrine are acting at these guys too
so you know on the heart you have these
uh beta adrenergic receptors so like
this one right there and this one right
there so these beta adrenergic receptors
let's say it's on the SA node if it's on
the SA node what can epinephrine or norepinephrine
norepinephrine
do they can B bind
onto this receptor and they stimulate
this beta adinc receptor by how
increasing the calcium influx increasing
the action potentials which does what to
the heart rate increases the heart rate
so what's the overall result here it's
going to increase your heart rate which
does what to your blood pressure
increases your blood pressure it's going
to activate these beta aeric receptors
on the contractile cardiac muscle cells
and cause an increase in contractility
what happens if you increase contract
ility you increase stroke volume if you
increase stroke volume you increase
cardiac output if you increase cardiac
output you increase blood pressure okay
so what is the overall result of these
two things an increase in blood pressure
let's actually show that so an increase
in this guy and an increase in this guy
all results in an increase
in blood pressure why do we want to
increase our blood pressure because by
increasing our blood pressure we help to
be able to get get as as much of these
nutrients to the vital tissues as
quickly as possible that's one reason
but you know it also can act on specific
uh types of adrenergic receptors Alpha
adrenergic receptors like certain blood
vessels in our
body by doing that if it acts here at
these adrenergic receptors let's say
that this is an alpha 1 adrenergic
receptor what can it do to the these
actual Alpha 1 adrenergic receptors
cause vasil constriction if you
cause Vaso constriction what happens if
you you have Vaso constriction of the
blood vessel Vaso
Vaso
constriction what happens what to the
Lumin diameter it decreases if the Lumin
diameter decreases what happens to the
resistance it goes up if the resistance
goes up what happens to your BP your BP
goes up your blood pressure right and
that should make sense why because we
want to get these nutrients that glucose
that fatty acids those glycerols to the
actual skeletal muscles or other vital
organs like the heart muscle so that it
can provide those different types of
increased activity so we can run away or
fight off that orangutang
okay okay what else have you ever
noticed do you ever notice that you know
your GI traed if you're actually having
um to run away from a orangutang and
let's say that you have a piece of pizza
that you just ate right so you got a
double pepperoni pizza and you just ate
it so let's say in here in here here's
your stomach and there's this like
double pepperoni pizza love pizza so good
good
but you have double pepperoni pizza with
the cheese stuff crust oh that's the
best okay but you're digesting this
pizza so are you going to be caring when
you're running away from aut Tang about
digesting the pizza no you don't give a
crap about that you'll you'll digest the
pizza later what's going to happen to
the blood vessels going to the actual GI
tract or the GI tract activity it's
going to decrease so you're going to
divert blood that's coming to the GI
tract away from it so that it can go to
the skeletal muscles or go to the lungs
or go to the heart muscle or to the
brain okay okay same thing with the
kidneys and the skin even in your
kidneys you're going to want to
constrict the blood vessels that are
going to the kidneys because you'll
worry about peeing later you don't want
to pee on the orangutang you want to be
able to hold that pee for later so
you're going to want to constrict the
blood vessels that are going to the
kidney to prevent that activity and
you're going to want to constrict the
blood vessels to your skin because
you're not really caring about the skin
activity at that point in time your
concern is getting as much blood and
nutrients to the skeletal muscles and
your heart muscle and your lungs and
your brain so that you can avoid by
fight or flight of that AR
okay so that's the goal
there now that being said what is it
going to do to your respiratory system
okay you ever notice that when you get
really really have a fight ORF flight
situation what happens you start
breathing really really heavy right so
it's going to want to increase the
actual amount of air or oxygen coming
into the lungs and increase the amount
of CO2 being
exhaled so if you actually know here you
have smooth muscles surrounding your
bronchi you have some smooth smooth muscle
muscle
there the sympathetic nervous system
actually comes over here let's say that
you have the epinephrine or the the
norepinephrine it's going to come over
here and it's going to act on that
smooth muscle when it acts on the smooth
muscle with inside of the bronchials
it's going to cause those bronchials to
do what it's going to actually dilate
the bronchioles if you dilate the
bronchials what's going to happen to the
amount of air that can flow in and out
it's going to increase so you're going
to have an increased air flow going in
and out so there's going to be an
increase in respiration so what will
happen here what's the overall result
with the lungs there'll be an increase in
in
respiration by how what's the mechanism
by which it does it it dilates the
bronchioles okay so that would be
working by some type of usually Alpha 2
adrenergic receptor right all right
engineer so throughout this video we
covered a lot of information about the
Adrenal medulla and the the pathway by
which it's being synthesized for the
norepinephrine epinephrine we talked
about its release we talked about its
stimulus via the uh sympathetic part of
the actual spinal cord from T1 to L2 we
talked about its effects on the target
organs and all of those amazing and
beautiful effects it does and you guys
can imagine that any kind of condition
in which there could be like a tumor in
this area and you're producing excessive
amounts of epinephrine and
norepinephrine could be potentially
disastrous on on specifically your blood
pressure and your glucose levels and
your respiration if you're interested
enough this is called foch chromosoma
okay it's whenever you have a tumor
within the adrenal medou it's usually
neuroblastoma and it causes excessive
amounts of epinephrine and
norepinephrine release and it's very
very dangerous so I I really hope all of
this made sense guys I hope you guys
really enjoyed it um and the in the next
video we're going to basically cover a
lot about all of the hyper and hypos
secretions I hope you guys enjoyed it
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