Ch. 35 Berne and Levy: Potassium, Calcium, and Phosphate balance

Question 1

What 3 external stimuli effect movement of K+ into cells, decreasing plasma K+?

Answer 1

insulin, epinephrine, aldosterone

Question 2

What percentage of K+ is reabsorbed?

Answer 2

85%

15% excreted

Question 3

What are the 3 principal factors regulating rate of K+ secretion by DT and CD?

Answer 3

1) Na,K-ATPase pump
2) tubular cell to tubular lumen electrochemical gradient (-40mV)
3) K+ permeability of apical membrane

Question 4

What two mechanisms mediate K+ secretion when there is a high plasma K+ conc?

Answer 4

1) Na,K-ATPase pulls K+ into the cell and that increases the permeability of K+ in the apical membrane allowing for K+ secretion
2) aldosterone (which stimulates Na,K-ATPase

Question 5

What effect does ADH have on K+ secretion?

Answer 5

NONE

Question 6

What are the 5 factors altering K+ secretion?

Answer 6

1) hormones (aldosterone)
2) tubular fluid flow (indirectly related to K+ secretion)
3) dietary intake of K+ (directly related)
4) acid-base status (acute = decrease sec; chronic = increase sec)
5) diuretics

Question 7

What are the K+ sparing diuretics?

Answer 7

spironalactone and amiloride

Question 8

What happens when Ca++ conc in the ECF is low??

Answer 8

parathyroid hormone is secreted which stimulates Ca++ reabsorption from the kidney

Question 9

What 3 things does parathyroid hormone do?

Answer 9

1) stimulates bone resorption
2) increases Ca++ reabsorption by kidneys
3) stimulates production of calcitriol which increases Ca++ absorption by the GI tract

Question 10

What does calcitriol do?

Answer 10

1) increase Ca++ resorption from the bone
2) decreases Ca++ excretion
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