- So we just talked about how urine is formed,
dilute versus concentrate.
We know that concentrated urine will help
to maintain the water balance.
Well, helping maintain water balance
will help to increase or decrease blood volume.
By increasing or decreasing blood volume,
that's one way to effect blood pressure.
So you have two more hormones here.
Aldosterone and renin.
Both aldosterone and renin can help
keep your salt, sodium chloride, in proper balance.
The proper amount of salt attracts
the proper amount of water.
Well, the kidneys also help with acid based balance.
Helps with the pH balancing and the pH buffering.
So it keeps the blood pH in the normal range.
The kidneys help control red blood cell production.
The kidneys can produce a hormone, erythropoietin.
That hormone will be secreted by the kidneys
when the kidneys realize there's
not enough oxygen in the blood.
So you can make more red blood cells.
More red blood cells means more oxygen transports.
Activating vitamin D.
Can take this inactive form and turn it
to an active form, the kidneys.
So really there's a lot of things the kidneys can do.
More than just this water balance we've mentioned before.
Now we start dealing with water balance and blood volume.
Blood volume and blood pressure are completely linked.
You can't really alter blood volume
without altering blood pressure
unless something else comes in the body.
So let's start dealing with how water balance
works on blood volume.
We look at the kidneys, the hypothalamus,
and posterior pituitary.
Well the hypothalamus is just the bottom of the brain.
Just part of your central nervous system.
Posterior pituitary is part of the
endocrine system, produces hormones.
We have these negative feedback loops
that help to regulate the hormone.
We're looking at AHD, or anti-diuretic hormone.
So if you have too much anti-diuretic hormone,
you conserve too much water.
Well if you conserve too much water,
you're gonna end up with basically
an overdose of water in your body.
Well if you don't have enough ADH,
anti-diuretic hormone, you can have
too little water in your body.
So we have this negative feedback loop
where if there's a problem, which means
too much or too little, it'll help to regulate
the amount of anti-diuretic hormone.
Well this also helps to deal with your thirst.
If you have enough fluids, you're hydrated,
you're not as thirsty.
But if you're dehydrated you'd need more fluid,
then you can increase your thirst.
So you say this term anti-diuretic,
well what really is a diuretic?
A diuretic will increase the formation
and excretion of urine.
That means it causes fluid to be lost in the body.
Lasix, a medication.
Caffeine, think coffee.
Alcohol, all those are diuretics.
They all cause an increase in fluid loss.
Now the case of Lasix, the medication,
a lot of times that's prescribed for high blood pressure.
If a person has high blood pressure,
they take Lasix, the drug there,
and it reduces the blood volume, reduces blood pressure.
Caffeine.
Well that causes problems with sodium reabsorption.
If you can't keep the proper levels of sodium
or salt in your body, you can't get enough water.
Alcohol, alcohol is directly works on anti-diuretic hormone.
Alcohol, the more you have, the more it inhibits ADH.
The more ADH is inhibited, the more fluid is lost
in the body because you're not trying to conserve any of it.
So how about aldosterone and renin?
Aldosterone and renin are both hormones.
Now aldosterone at least will be pretty much
indirectly dealing with a decreased blood volume
or decrease in blood pressure.
Because aldosterone itself will
help with sodium reabsorption.
So what ends up happening is when blood volume
or blood pressure goes down,
the kidneys release renin.
Renin goes this whole series of reactions,
something called angiotensin II.
And don't worry about what the reactions are in between.
The important part is renin from the kidneys
ends up being converted to angiotensin II.
Angiotensin II will cause the release of aldosterone.
So really renin and aldosterone are pretty much interlinked.
Renin from the kidneys eventually
makes it into angiotensin II.
Angiotensin II causes the release of aldosterone
from the adrenal glands.
Aldosterone causes an increase in sodium reabsorption
therefore more sodium coming in,
means it'll attract more water in.
So it's helping to increase blood volume
or increase blood pressure.
So what we're going to do is we're going
to start with this blood volume decreasing,
so we're at the top middle.
If your blood volume decreases,
what's gonna happen is it's gonna trigger your kidneys.
The kidneys will release renin.
Renin will eventually go through
and be converted to angiotensin II.
That converts to aldosterone.
So angiotensin II causes aldosterone to be released.
The release of aldosterone will help conserve salt.
The more salt you keep, the more water
will therefore follow the salt,
helping to increase blood volume.
Pretty much water follows salt.
So keep more salt, keep more water.
But another way to do it is look at the top left.
Anti-diuretic hormone.
Increased anti-diuretic hormone means
increasing more water conservation.
Blood volume goes up.
We've already mentioned that the kidneys help with
an acid-base balance, that's blood pH balance.
Well this gives a little more of how it works.
Your blood pH has to stay between
7.35 and 7.45.
Now that's not really a very large range there.
A tenth is all you get to move around.
So one way that pH is regulated is the kidneys.
There's a lot of buffers that interact.
There's also lungs that play a part.
So it's not just the kidneys.
There's one of many parts in the pH regulation.
The way the kidneys help to maintain pH
is they reabsorb filtered bicarbonates.
The bicarbonate that's reabsorbed
is a major buffer in the blood.
So by keeping more of it in the system,
it helps to keep more of a buffer going.
The kidneys can also secrete acid.
Get rid of acid, get rid of hydrogen ions.
That way it helps to also reduce the amount of fluctuation.
The hormone erythropoietin.
Well if you start with a decrease in the amount of oxygen,
this could be the fact that there's
not as much oxygen in the environment,
your red blood cells aren't carrying the oxygen,
whatever it is.
Something has caused the amount of oxygen
in your blood to go down.
So therefore if you decrease the amount of oxygen,
the kidneys can pick it up.
They can sense it.
They can secrete erythropoietin, a hormone.
The erythropoietin is going to cause
an increase in red blood cell production.
By making more red blood cells,
there's more cells that can carry oxygen
which means you will have an increase,
traditionally at least, an increase,
in oxygen content of the blood.
So erythropoietin, red blood cell production.
And this vitamin D.
When your skin is exposed to sunlight,
what ends up happening is it'll produce
an inactive form of vitamin D.
Now you can't go out there and sit in the sun
for three or four hours and say I got tons of vitamin D.
Doesn't work that way.
Usually about 20 to 30 minutes of exposure
will max out the production of this inactive vitamin D form.
So 20, 30 minutes of sun exposure is pretty much
walking back and forth to a vehicle,
maybe you're outside doing something for a few minutes.
It adds up throughout the day.
The trick is, you have to have the sun out.
So depending on the environment,
you might have a string of days of cloudy days.
It helps, ends up with a reduction of vitamin D then.
But thankfully you get some vitamin D
in your food anyways, so it's not the end of the world.
But this inactive form of vitamin D is transported to liver.
Once transported it's modified.
The vitamin D, the inactive form,
is then converted to an active form by the kidneys.
So follow this through.
Sun exposure on the skin produces
an inactive form of vitamin D.
That inactive vitamin D form goes to the liver,
it's modified a little.
From there, the inactive vitamin D
is converted to an active vitamin D,
the real vitamin D, by the kidneys.