Renal: Water

Question 1

net water gain per day

Answer 1

none

Question 2

which regions of nephron does water reabsorption occur

Answer 2

70% in the PT, 15% in the loop, 15% in the dct and cd

Question 3

which regions of nephron does glucose get reabsorbed

Answer 3

only the pt

Question 4

when you have no water, what do you want to happen to urine flow rate

Answer 4

you want it to decrease, you want to preserve more water

Question 5

when you have excess water, what do you want to happen to urine flow rate

Answer 5

you want it to increase, because you want to get rid of the excess

Question 6

what compartment senses water volumes

Answer 6

the ICF, using specialized cells

Question 7

what do the SON and PVN do

Answer 7

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.

Question 8

where are hypothalamic osmoreceptors

Answer 8

in the OVLT in the anterior hypothalamus

Question 9

what happens when hypothalamic osmoreceptors shrink

Answer 9

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

Question 10

describe pathway from shrunken cells in OVLT to AVP release

Answer 10

osmoreceps shrink
channels open
cations enter, depolarization
ap generation
increased AVP secretion
increased thirtst

Question 11

ADH vs AVP vs VASOPRESSIN. whats this pathway?

Answer 11

all the same

cells shrink
ap sent
avp made in hypo
vesicles transported
avp secreted in post pit
acp rleased into blood

Question 12

how does plasma osmolality impact vasopressin secretion

Answer 12

high osmo, cells will shrink, vaso released

Question 13

how does brain respond to hypoosmolality vs hyper osmolality

Answer 13

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

Question 14

contrast hyper vs hypo osmolality

Answer 14

hyper = high conc
hypo = low conc

Question 15

how is a concentration gradient created in the loop of henle

Answer 15

by water permeability and sodium transport

countercurrent multiplication:
most conc at the bottom of the loop of henle

Question 16

describe the concentrations of fluid as it passes through the nephron

Answer 16

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

Question 17

describe pathway by which vasopressin increases water in the blood (reabsorption)

Answer 17

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

Question 18

impact of vasopressin on urination

Answer 18

vasopressin decreases urination (more water reabs)

Question 19

how does urine get concentrated

Answer 19

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.

Question 20

how does drinking water increase urine flow rate

Answer 20

swelled hypothal, no shrinkage, reduced ap, no avp released, no water perm, more water in urine, inc urine flow rate

Question 21

does the collecting duct have water channels without ADH

Answer 21

nope, mostly imperm

Question 22

when would you excrete dilute urine? how does this happen?