So we are continuing our series of videos on blood pressure and in previous
videos I talked about the three elements so heart rate, stroke volume, and
peripheral resistance, and how it impacts our cardiac output. I've also talked
about baroreceptors - those things that measure and evaluate the amount of
stretch and recoil in our vessels and help our body to retain the blood
pressure. And in this video we're going to talk about the
renin angiotensin aldosterone system; one of my favorites because it's such a
complex and beautiful system. I can't wait to get into it let's head to the
board. Welcome back my name is Tammy and this is NurseMinder and on this channel
we do everything nursing so if you're new here consider subscribing below so
that you get the next video when it's released. Now our second compensatory
system is the renin-angiotensin aldosterone system or in short
RAAS system but this one, unlike the baroreceptors that gets its start in the
cardiac system right off the aortic arch there, this one actually gets its start
in the kidneys. Now the kidneys also require a certain
amount of fluid or pressure in order to do their job. Now this information from the
heart and the kidneys will become important when we talk about beta 1
blockers but for now we're going to talk about the renin-angiotensin-aldosterone
system. Ok so we're going to build this system out slowly so as not to
overwhelm you with how busy this board is going to get. Now I mentioned that the
renin-angiotensin-aldosterone system gets its start in the kidneys and
there's two places in particular that are monitoring for changes in pressures,
so that stretch in those arteries and changes in salt. So one part is the
afferent arteriole, they're bringing the blood into the glomerulus. They have
these juxtago, justago,
juxtaglomerular cells that are lining the afferent arterioles and their sole
purpose is to measure the pressure, so stretch of the arteries which is related
to water, and the sodium concentration in the distal convoluted tubules. That's the
second place in the kidneys where we have juxtaglomerular cells monitoring
for salt concentratio. Both of those locations can signal for a release of
renin. So the juxtaglomerular cells are the ones that are responsible for
synthesizing and maintaining, synthesizing and storing
renin, and then of course when it's required, releasing it. So as you can see
renin is the first step and that's why it's called renin now we're going to
talk about how we get angiotensin. Okay so right now we have just come from a
decrease in pressure or salt noticed in the kidneys and that the juxtaglomerular
cells have been triggered to release renin. Renin is now in the bloodstream
where it will meet up with angiotensinoge. Now angiotensinogen is
produced by the liver, this is a multi organ system, it's fascinating! The liver
produces angiotensinogen, this is an inactive hormone, but when renin meets
up with it, it actually cleaves is the word it puts it into a different state
and it's called angiotensin one. Now this is still not at its final state so it is
still an inactive hormone in this stage. Alright guys, now I know this is a lot of
information coming at you so if you're learning something already and you're
enjoying this give it a thumbs up, and we're gonna get into the rest of that
system right after this - so just take a big breath - ah - let's dive in! Angiotensin
one then travels to the lungs where it is then transformed into
angiotensin 2. So the way that I remember the different organs and how they're
involved is I know that renin is where it starts so that is the kidney. I know that
the liver, there's one liver, so that's going to give me angiotensinogen
that meets up with renin and becomes angiotensin one. I have two lungs and
this is where that chemical change occurs to give me angiotensin 2. So
activation of angiotensin 1 occurs in the lungs where there's another coenzyme
in the capillary beds and that converts it to angiotensin 2. Now angiotensin 2 is
what does the work - this is the word horse, so we're going to look at that
next. Now when angiotensin 2 hits its target cells, it's going to cause
vasoconstriction - that's really important because this is what's going to narrow
those arteries and it's going to increase blood flow back into the
afferent arteries, arterioles that are traveling to the kidneys, which will stop
this process because now the juxtaglomerular cells have identified we
have increased pressure and so there's no need to release renin.
Ok so that takes care of the renin and the angiotensin. Where does the
aldosterone come in? Well we know aldosterone is part of the kidneys so
we're going to take a look at that next. Okay so we got angiotensin 2 will cause
vasoconstriction, it's known as a very powerful phase vasoconstrictor and that's
great it's going to increase my blood pressure but there's more to this.
Angiotensin ii also affects the adrenal glands, so that's a little hat on top of
the kidney, but in particular it's gonna go straight to the cortex. Now the cortex
has 3 different hormones it can secrete, different classifications, and so one is
mineral corticoids the second is glucocorticoids and the third is
androgens. In this case we are focusing on mineralocorticoids. This is where
aldosterone is produced. Okay so we've covered a lot of ground and we're almost
done. When aldosterone is released it actually
works on the kidney itself so it's meant to increase sodium and water retention
in the kidney. Now I know it's not mentioned here but there's one more
thing that's happening and that's in the brain. It has what's
called Osmoreceptors and it's gonna release antidiuretic hormone, anti -
against, diuresis - losing urine, and so this will also help to further increase
the volume of our blood. We have covered a lot in this video! We've journeyed from
the kidney in the blood stream meeting up with the angiotensinogen that's
produced by the liver, converting it into angiotensin one along
the route to the lungs where it's then converted to angiotensin ii which then
goes back to the kidney and has an effect and also stimulates the release
of aldosterone from the cortex and the brains of it involved in this little gig
as well secreting ADH - antidiuretic hormone. That is a lot of people working
to keep our blood pressure in the normal healthy range. So you can imagine that
there's breakdown in any one of these places there's going to be trouble and we're
going to talk about some of those treatment methods in upcoming videos.
Until next time, make it a great day :)