Renal: Water Flashcards
net water gain per day
none
which regions of nephron does water reabsorption occur
70% in the PT, 15% in the loop, 15% in the dct and cd
which regions of nephron does glucose get reabsorbed
only the pt
when you have no water, what do you want to happen to urine flow rate
you want it to decrease, you want to preserve more water
when you have excess water, what do you want to happen to urine flow rate
you want it to increase, because you want to get rid of the excess
what compartment senses water volumes
the ICF, using specialized cells
what do the SON and PVN do
both located in the hypothalamus, send signals to the pituitary grand to secrete vasopressin, activates vaso pressin receptors, reabsorbs water.
this would happen when you have really high water intake.
where are hypothalamic osmoreceptors
in the OVLT in the anterior hypothalamus
what happens when hypothalamic osmoreceptors shrink
when they shrink, action potentials increase and you get more thirtsy.
it should make sense then when they swell, you dont need to drink anymore water
describe pathway from shrunken cells in OVLT to AVP release
osmoreceps shrink
channels open
cations enter, depolarization
ap generation
increased AVP secretion
increased thirtst
ADH vs AVP vs VASOPRESSIN. whats this pathway?
all the same
cells shrink
ap sent
avp made in hypo
vesicles transported
avp secreted in post pit
acp rleased into blood
how does plasma osmolality impact vasopressin secretion
high osmo, cells will shrink, vaso released
how does brain respond to hypoosmolality vs hyper osmolality
if its low conc that means you have enough/excess water. so you will intake less water (less thirst). you will also urinate more, and have less avp (bc youre not thirsty)
if its hyperosmo you need more water, more thirty, antidiuretic, and more avp
contrast hyper vs hypo osmolality
hyper = high conc
hypo = low conc
how is a concentration gradient created in the loop of henle
by water permeability and sodium transport
countercurrent multiplication:
most conc at the bottom of the loop of henle
describe the concentrations of fluid as it passes through the nephron
isoosmotic in pt
descending - more water leaves, so more conc
in tal- solute leaves so conc decreases
dct and cd - variable reabs, depedning on hormone activation
urine osmo depends on what was reabs in the collecting duct
describe pathway by which vasopressin increases water in the blood (reabsorption)
it binds to a MEMBRANE GCPR (as opposed to aldosterone that binds to a cytoplasmic receptor)
that receptor activates camp
makes aquaporin vessels insert into apical (luminal) membrane
water can go into the cell through the channels, and out into the blood
impact of vasopressin on urination
vasopressin decreases urination (more water reabs)
how does urine get concentrated
the medulary interstitium is super conc bc of the countercurrent mult, na from tal, and urea
vasopressin will open the channels to reabsord water, because it wants to balance out the super salty outside
in the process the urine loses water.
how does drinking water increase urine flow rate
swelled hypothal, no shrinkage, reduced ap, no avp released, no water perm, more water in urine, inc urine flow rate
does the collecting duct have water channels without ADH
nope, mostly imperm
when would you excrete dilute urine? how does this happen?
