The last little bit that we have in a nephron.
Never thought we will get
here and here we are already. One of those
things during the journey at sometimes feels
like it is perhaps a little taxing but once
we actually get here, then it is not so bad
and what do you want to do later is keep reviewing,
reviewing, reviewing, be able to answer the
questions that I have been posing at you. Be
able to identify the patients that I have
been giving you over and over again and that
way the more number of times you go through
this the easier it becomes and the more that
you are able to integrate the material as
needed. Where we are now is an epsilon or collecting duct.
We took a look at this picture earlier once
again quickly recap. We have the urine luminal
side on the left. On the right is your blood
interstitium. That green cell that you are
seeing there is, in fact, the epithelial cell.
One will be the principal because we are in
the collecting duct, the other one would be
in fact your intercalated. Next what kind of
receptors do we have here
when dealing with two other major hormones?
We have an aldosterone receptor and we have
an ADH receptor known as V2 receptor. Aldosterone
is what our topic here will be as we peruse
through this lecture series and aldosterone
could potentially work on two sides of the
cell. If it is on the side of the luminal
membrane or apical, it then works on the ENAC.
What does that mean to you again? Epithelial
Sodium Channel whereas if it works on your
sodium-potassium pump that would be on the
basolateral all in the hopes of doing what,
please? Reabsorption of sodium. What kind
of effect does aldosterone have on hydrogen?
It gets rid of it. So therefore if you have
excess and you have an increase in pH. It
gets rid of your potassium, what kind of effect
would that have? Obviously, if there is too
much aldosterone, it results in hypokalemia.
Once again if you have hypokalemia, then how
is your patient going to present? Tired, fatigued
because of muscles that are not working properly.
Finally, get difficult to reach the threshold,
and the heart obviously is an issue. Collecting
tubule when dealing with the principal cell
let us look at sodium and potassium. If we
are dealing with intercalated, the hydrogen. Aldosterone
results in increased sodium reabsorption. And
then ADH here as you see of two kidneys does
as the V2 receptors. ADH, as we talked about
earlier, is responsible for strictly inserting
your aquaporin and as long as what the pending
is to the osmolarity of the plasma. The example
that I gave earlier was severe sweating. You
taste yourself and you taste salty, but
you are losing more fluid, are you not?
So, therefore, it is hypotonic loss of sodium.
When you are losing that amount of fluid,
then you know that your plasma osmolarity
increases. Your osmoreceptors are very sensitive
up by the hypothalamus resulting in release
of ADH, which then flows down in neurophysins
in your infundibulum into the posterior pituitary
and out it comes. Are we clear? It also
has effect on your V1 receptors and
vasopressin is what it is called.