Water Balance

Question 1

Two key stimuli for increased ADH secretion?

Answer 1

1. increased plasma osmolarity (more sensitive)

2. blood volume depletion

Question 2

Secondary stimuli for ADH secretion:

Answer 2

pain

nausea

drugs (narcotics in particular)

Question 3

Pathway for ADH secretion with increased plasma osmolarity:

Answer 3

Brain osmoreceptors depolarize –>

stimulates supraoptic nuclei in hypothalamus –>

Neurosecretory cells in posterior pituitary secrete ADH

**thirst is also stimulated

Question 4

Pathway for ADH secretion by decreased plasma volume:

Answer 4

low MAP –> carotid and atrial baroreceptors –>

parasympathetic stim of hypothalamus paraventricular nuclei –> neurosecretory cells in post pituitary –> increased ADH secretion

Question 5

Only nephrons that control water:

Answer 5

juxtamedullary (loops dive way down into medulla, glom still in cortex)

Question 6

Variability of water reabsorption by percent?

Answer 6

80-99.5%

Question 7

With full ADH effect, how much water gets excreted?

Answer 7

0.5%…..

Question 8

With NO ADH effect, how much water can be excreted?

Answer 8

20%…36 L

Question 9

Water % reabsorbed in prox tubule?

Answer 9

65%

Question 10

Water % reabsorbed in descending LoH?

Answer 10

10% (vs 20% NaCl)

Question 11

What joins NaCl in the interstitium around the lower loop of henle to increase osmolarity when ADH is in effect?

Answer 11

urea

Question 12

Go learn about urea in lecture notes.

Answer 12

Not very flashcardable.

Question 13

ADH deficiency?

Answer 13

Diabetes insipidus

Question 14

If diabetes insipidus corrects with exogenous ADH the it’s called?

Answer 14

Neurogenic

don’t make ADH

Question 15

If diabetes insipidus does not correct with exogenous ADH, then it is called?

Answer 15

Nephrogenic

kidney doesn’t respond to ADH (mutation of V2 receptor)

Question 16

ADH receptor that stimulates transcription of aquaporins that get stored in intracellular vesicles for release to membrane?

Answer 16

V2

Question 17

Player in the V2 receptor signaling pathway:

Answer 17

ATP

cAMP

Protein kinase A

cAMP response element binding protein (CREB)

CREB-P – the transcription factor

Question 18

AQP2 inserts where?

Answer 18

luminal membrane (collecting tubule)

Question 19

AQP 3&4 insert where?

Answer 19

basolateral membrane

Question 20

Drug that can cause diabetes insipidus?

Answer 20

lithium

Question 21

V2 receptor antagonist used in HF?

Answer 21

tolvaptan

Question 22

Most important aquaporin?

Answer 22

2 (luminal)

Question 23

If you don’t eat any protein or solutes, what happens?

Answer 23

No gradient formation in deep medullary region

no ability to resorb water because no urea or NaCl

“tea and toast”

“beer potomania”

Question 24

Location of UT1?

Answer 24

distal third of collecting tubule

Question 25

Location of UT2?

Answer 25

ascending LOH

Question 26

UT1/2 upregulated by?

Answer 26

ADH