These two bullet points as simple as it may
seem have profound meaning. Listen. Normally
body fluid volume, how do you control this?
Let me bring in the hormone aldosterone. With
aldosterone, when it kicks in, it wants to
do what? Reabsorb the sodium. As soon as you
reabsorb the sodium, does it affect osmolarity
or does it affect more of the volume? Interesting.
For example, if you talk about aldosterone
and increasing blood pressure and you are
reabsorbing your sodium, does that increase
more of your systolic or diastolic blood pressure?
Mean to say that sodium fluid comes in. It puts
more fluid or volume into the heart. You increase
your stretch thus you increase your systolic
blood pressure. So there I need you to understand
how profound it is to say the sodium balance
then regulates your volume. Aldosterone will
be a prime example of a hormone. Versus now
here the theme of the sentence is osmolarity
the primary determinant for this, of course,
being your sodium concentration, regulated
by well this would be osmolarity. So what
hormone are you thinking about here? What
are those called by the hypothalamus that
detects the osmolarity of the plasma? I believe
they are called osmoreceptors. Oh well, there
it is. So osmoreceptors is then going to
regulate the release of ADH, but then what
does ADH do? Only works to reabsorb water and
so the water then dictates as to what happens
to the osmolarity. Fascinating statement, aren't
they? The common theme, the first statement
aldosterone being your example, the second
one would be ADH. Let us further move on.
Regulation of water, key points.
Changes in sodium balances, thus what? Changes
in volume status. We just got them talking
about aldosterone. Changes in water balance
then changes your sodium concentration, we have
osmolarity. Certain pathologic conditions
in which, well, may I ask you something? What
is the most tightly regulated type of parameter?
What would be the volume or more so the osmolarity
on a regular basis between you and I right
now? Here I am and I am lecturing my butt off for
a number of hours and as I do so, then I can
expect there to be evaporation of water? Sure.
So therefore on a regular basis, you think
it is more amount of volume that has been
affected or it's osmolarity? That is an important
physiologic question. The osmolarity is the
one in which it is being tightly regulated.
Certain times, however, you might have a crossover
where you are losing so much volume that the
osmolarity is actually sacrificed. All I am
doing here is introducing topics and concepts
to you and as you move on we are going to
obviously plug in the details. The cross
over effect is something we should pay attention