Renal 3: Water Balance

Question 1

the kidneys regulate water excretion to maintain constant __ and ___

Answer 1

body fluid osmolarity and solute concentrations

Question 2

ADH is secreted by the ____ and its levels in the blood are controlled by blood ___, ____ and ___

Answer 2

posterior pituitary gland; volume, pressure, osmolarity

Question 3

t/f the osmolarity of urine changes greatly as it travels through the nephron

Answer 3

true

Question 4

bc water cannot move across some parts of the loop of henle, the osmolarity of interstitial fluid is also not constant but shows a ____

Answer 4

corticocapillary osmotic gradient

Question 5

the ____ in the loop of henle results in osmotic gradients in both the urine and interstitial fluid

Answer 5

countercurrent osmotic gradient

Question 6

___ reabsorption in the collecting duct makes a large contribution to high interstitial fluid osmolarity

Answer 6

urea

Question 7

average daily urine output

Answer 7

1.5 L

Question 8

daily urine output can be as little as __-

Answer 8

0.5 L

Question 9

daily urine output can be as much as ___

Answer 9

20 L

Question 10

water balance is ahomeostatic mechanism controlled by the ___

Answer 10

kidneys

Question 11

what is water diuresis

Answer 11

formation of dilute urine

Question 12

the kidneys can rapidly alter urine flow rate and urine osmolarity in order to maintain near constant ___ and ___

Answer 12

plasma osmolarity and urine solute concentration

Question 13

what are the characteristics of urine when ADH is high?

Answer 13

hyperosmotic (concentrated, low volume)

Question 14

what are the characteristics of urine when ADH is low?

Answer 14

hypoosmotic (dilute, high flow)

Question 15

when ADH is low there is no water reabsorption in the __

Answer 15

distal tubule and collecting duct

Question 16

ADH increases water permeability by increasing the amount of ____ channels in the ___ membrane

Answer 16

aquaphorin 2 water; apical

Question 17

describe the pathway of how ADH icreases AQP2

Answer 17

ADH stimulates the Gs ADH receptor, producing cAMP / PKA which phosphorylates the AQP2

Question 18

location of AQP2 when ADH is low

Answer 18

dephosphorylated and moved to vessicles

Question 19

location of AQP2 when ADH is high

Answer 19

phosphorylated in the apical membrane

Question 20

plasma osmolarity ___ in low ADH

Answer 20

increases

Question 21

plasma osmolarity __ in high ADH

Answer 21

decreases

Question 22

travelling from the cortex to the medulla, the corticopapillary osmotic gradient / interstitial fluid osmolarity ___

Answer 22

increases

Question 23

fluid leaving the proximal tubule and into the loop of henle is ___

Answer 23

isoosmotic

Question 24

osmolarity of fluid at tip (apex) of the loop of henle

Answer 24

hyperosmotic

Question 25

osmolarity of the fluid entering the distal tubule

Answer 25

hypoosmotic

Question 26

fluid in the descending limb of the loop of henle will always be ___ wrt the interstitial fluid

Answer 26

isoosmotic

Question 27

NaCl is absorbed without water in the ascending loop, which ___ urine osmolarity and ___ interstitial fluid osmolarity

Answer 27

decreases; increases

Question 28

countercurrent exchange in the loop of henle generates ___

Answer 28

corticopapillary osmotic gradient

Question 29

in the formation of dilute urine, in the descending loop, urine osmolarity ___ due to water reabsorption, equilibration with interstitial fluid osmolarity

Answer 29

increases

Question 30

in the formation of dilute urine in the ascending loop, urine osmolarity ___ as salt is reabsorbed without watser

Answer 30

decreases

Question 31

in the formation of dilute urine in the collecting duct, salt is reabsorbed w/o water, resulting in ___ urine

Answer 31

high volume; dilute

Question 32

blood is supplied to the nephron by what BV?

Answer 32

vasa recta

Question 33

in the formation of concentrated urine, high ADH has what effect on the distal tubule / collecting duct?

Answer 33

allows more water to be reasorbed to the blood rather than remaining in the urine

Question 34

urea reabsorption __ intersitial fluid osmolarity

Answer 34

increases

Question 35

~___% of interstitial fluid osmolarity is due to ___ under high ADH concentrations

Answer 35

urea

Question 36

urean diffuses from tubular fluid into interstitial fluid of the ___

Answer 36

inner medulla

Question 37

in the vasa recta, there is ___- of solute and water between blood and interstitial fluid

Answer 37

free exchange

Question 38

in the vasa recta, the blood osmolarity is similar to ___

Answer 38

interstitial fluid