Renal 3: Water Balance Flashcards
the kidneys regulate water excretion to maintain constant __ and ___
body fluid osmolarity and solute concentrations
ADH is secreted by the ____ and its levels in the blood are controlled by blood ___, ____ and ___
posterior pituitary gland; volume, pressure, osmolarity
t/f the osmolarity of urine changes greatly as it travels through the nephron
true
bc water cannot move across some parts of the loop of henle, the osmolarity of interstitial fluid is also not constant but shows a ____
corticocapillary osmotic gradient
the ____ in the loop of henle results in osmotic gradients in both the urine and interstitial fluid
countercurrent osmotic gradient
___ reabsorption in the collecting duct makes a large contribution to high interstitial fluid osmolarity
urea
average daily urine output
1.5 L
daily urine output can be as little as __-
0.5 L
daily urine output can be as much as ___
20 L
water balance is ahomeostatic mechanism controlled by the ___
kidneys
what is water diuresis
formation of dilute urine
the kidneys can rapidly alter urine flow rate and urine osmolarity in order to maintain near constant ___ and ___
plasma osmolarity and urine solute concentration
what are the characteristics of urine when ADH is high?
hyperosmotic (concentrated, low volume)
what are the characteristics of urine when ADH is low?
hypoosmotic (dilute, high flow)
when ADH is low there is no water reabsorption in the __
distal tubule and collecting duct
ADH increases water permeability by increasing the amount of ____ channels in the ___ membrane
aquaphorin 2 water; apical
describe the pathway of how ADH icreases AQP2
ADH stimulates the Gs ADH receptor, producing cAMP / PKA which phosphorylates the AQP2
location of AQP2 when ADH is low
dephosphorylated and moved to vessicles
location of AQP2 when ADH is high
phosphorylated in the apical membrane
plasma osmolarity ___ in low ADH
increases
plasma osmolarity __ in high ADH
decreases
travelling from the cortex to the medulla, the corticopapillary osmotic gradient / interstitial fluid osmolarity ___
increases
fluid leaving the proximal tubule and into the loop of henle is ___
isoosmotic
osmolarity of fluid at tip (apex) of the loop of henle
hyperosmotic
osmolarity of the fluid entering the distal tubule
hypoosmotic
fluid in the descending limb of the loop of henle will always be ___ wrt the interstitial fluid
isoosmotic
NaCl is absorbed without water in the ascending loop, which ___ urine osmolarity and ___ interstitial fluid osmolarity
decreases; increases
countercurrent exchange in the loop of henle generates ___
corticopapillary osmotic gradient
in the formation of dilute urine, in the descending loop, urine osmolarity ___ due to water reabsorption, equilibration with interstitial fluid osmolarity
increases
in the formation of dilute urine in the ascending loop, urine osmolarity ___ as salt is reabsorbed without watser
decreases
in the formation of dilute urine in the collecting duct, salt is reabsorbed w/o water, resulting in ___ urine
high volume; dilute
blood is supplied to the nephron by what BV?
vasa recta
in the formation of concentrated urine, high ADH has what effect on the distal tubule / collecting duct?
allows more water to be reasorbed to the blood rather than remaining in the urine
urea reabsorption __ intersitial fluid osmolarity
increases
~___% of interstitial fluid osmolarity is due to ___ under high ADH concentrations
urea
urean diffuses from tubular fluid into interstitial fluid of the ___
inner medulla
in the vasa recta, there is ___- of solute and water between blood and interstitial fluid
free exchange
in the vasa recta, the blood osmolarity is similar to ___
interstitial fluid
