l13 osmoregulation (water balance)

Question 1

in antidiuresis, high adh, how is urea affected?

Answer 1

in antidiuresis, when plasma adh is high, water is reabsorbed from collecting ducts so urea concentration is high in CD. adh increase urea permeability and urea moves into the interstitium and is recycled. in antidiuresis, the urine osmolality is higher (1200 mosm, low volume 0.5l). in low adh, diuresis, more urea is excreted and not recycled (urine concentration 50 mosm, high volume 10% gfr or 18l). urea recycling is important for renal concentration

Question 2

name 4 general roles of adh

Answer 2

• increases water reabsorption in cd by increasing AQP2
• increases salt transport TAL to keep interstitium osm high
• decreases vasa recta flow to prevent washout to keep interstitium high
• increases urea transport IMCD to keep interstitium osm. high

Question 3

what are the water transporters in cd, and what are they regulated by

Answer 3

basolateral aqp3/4, luminal side aqp2 and it is regulated by adh

Question 4

how is the interstitial osm. profile maintained

Answer 4

countercurrent exchange vasa recta

Question 5

how are hypothalamic neurons that secrete adh regulated (5)

Answer 5

• osmoreceptors stimulate when high plasma osmolality
• baroreceptors/cardiopulmonary normally inhibit, when low ECV or hemorrhage they stop firing (inhibition stops) and adh secreted (volume depletion 10%)
• low salt/water stimulates angiotensin 2 - adh
• natriuretic hormone- inhibits adh
• alcohol/drugs can change adh

Question 6

at what volume depletion is adh secretion triggered by baroreceptor/cardiopulmonary receptors

Answer 6

volme depletion of 10% (salt/water imbalance, or hemorrhage)