Water Balance

Question 1

What is the hypothalamic Osmoreceptor?

Answer 1

it’s located in the anterior hypothalamus (OVLT). it is strech-inhibited cation channels.
When osmoreceptor cells shrink, channels open, cations enter and depolarize cell leading to action potentials which lead to increased VP secretion and increased thirst

Question 2

What are the actions of Vasopressin?

Answer 2

binds to V2 receptor on basolateral membrane of DCT and CD cells
-signals via cAMP
-insertion into luminal membrane of water channels - aquaporin 2
huge increase in water permeability of collecting duct cells
*V1 receptors on blood vessels cause vasoconstriction

Question 3

Blood becomes progressively concentratted as vessesls enter the inner _____, this always for very ____ concentrations in the _____.

Answer 3

medulla, high, urine

Question 4

serum sodium >135

Answer 4

stimulates vasopression

Question 5

serum sodium >145

Answer 5

stimulates thirst

Question 6

What is the overview of urine concentration throughout the nephron?

Answer 6

Isosmostic fluid gets more concentrated down the descending limb, ions are reabsorbed back into the body in the ascending limb (not water), hormones control what happens in the distal tubule and depending on what the body needs will determine the concentrtaion of urine in collecting duct

Question 7

What is hypoatremia?

Answer 7

too much water
it is common
failure to suppress ADH (vasopressin)
happens because of reduced effective circulating volume like heart failure which has low output and blood pressure, and/or baroreceptors are activated to increase vasopressin secretion.

Question 8

What are the consequences of hypoatremia?

Answer 8

brain cells can swell, pressure on intracranial, seizures, coma, death. if it occurs slowly though brain cells can adapt

Question 9

What is hyperatremia?

Answer 9

much less common, problem with thirst or intake of water or loss of water

Question 10

what are the consequences of hyperatremia?

Answer 10

brain cells shrink, may be seizures, coma, death

chronic - then brain cells can adapt by adding new osmoles and protecting their volume

Question 11

What is Polyuria?

Answer 11

It is a large volume of urine. deficiency of vasopressin or kidneys can’t respond to it (abnomal V2 (x-linked disorder) or abnormal aquaporin 2)
excessive intake of water, osmotic diuresis, can be caused by a hemorrhage