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Physiology II > Renal Physiology: Ion Regulation > Flashcards

Renal Physiology: Ion Regulation Flashcards

1
Q

Resting membrane potential depends on the concentration gradient of what electrolyte?

A

potassium

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2
Q

This ion has a major role in the excitability of nerve and muscle tissue…

A

potassium

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3
Q

What is ECF potassium concentration a function of?

A

amount of K in body

distribution between ICF and ECF

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4
Q

What percent of potassium is located inside the cells?

A

98%

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5
Q

What three hormones exert control on potassium?

A

Epinephrine

Insulin

Aldosterone

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6
Q

Epinephrine’s activation of alpha-1 receptors causes what, which could lead to what condition?

A

shift of potassium out of cells

hyperkalemia

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7
Q

Insulin has what two effects on potassium?

A

increase uptake

stimulates sodium-potassium ATPase

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8
Q

Aldosterone has what three effects on potassium distribution?

A

increases potassium uptake to tubule

increases potassium excretion

stimulates sodium-potassium ATPase

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9
Q

Acidoses causes potassium to move where?

A

out of cells

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10
Q

Alkalosis causes potassium to move where?

A

into cells

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11
Q

Does transport of potassium in the PT and LOH change with changes in total body potassium?

A

no

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12
Q

Where does physiological regulation of potassium occur?

A

DT and CD

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13
Q

The magnitude of potassium secretion depends on the size of what?

A

electrochemical gradient across luminal membrane

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14
Q

The below factors have what effect on potassium secretion?

Increased dietary intake

Aldosterone presence

Alkalosis

High urine flow rate

Increased sodium to distal nephron

A

increase

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15
Q

What causes the secretion of potassium when sodium loads in the distal nephron increase?

A

stimulates sodium-potassium ATPase

intracellular potassium increases, and is then secreted

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16
Q

Which drugs cause an increased delivery of sodium to distal nephron, and therefore can lead to hypokalemia?

A

loop diuretics

thiazides

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17
Q

Which two diuretics are potassium sparing?

A

spironolactone and amiloride

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18
Q

What stimulates aldosterone?

A

high plasma potassium levels

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19
Q

How does aldosterone promote potassium secretion?

A

stimulates basolateral sodium-potassium ATPase

Increases luminal membrane permeability to potassium

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20
Q

Aldosterone increases potassium secretion in the DT from ____ to _____ %

A

10-50%

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21
Q

Aldosterone increases potassium secretion in the CD from _______ to ______ %

A

5-30%

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22
Q

In which cell type does potassium secretion (as regulated by aldosterone) occur?

A

principal cells

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23
Q

Aldosterone stimulates the upregulation of which two channels in the principal cells?

A

Apical potassium channels

sodium potassium ATPases

24
Q

Aldosterone causes increased tubular reabsorption of _______ and increased tubular secretion of ______

A

reabsorption of sodium

Secretion of potassium

25
Q

What two factors cause an increase in aldosterone secretion?

A

increased AT II

Increased plasma potassium

26
Q

A low potassium diet causes what homeostatic response?

A

decreased excretion

27
Q

In a low potassium diet, what percent of filtered potassium is reabsorbed and where?

A

87% reabsorbed in the PT and LOH

28
Q

The PT and LOH reabsorb 87% of filtered potassium in low potassium conditions. Where is the remaining potassium reabosorbed?

A

distal nephron (DT/CD)

29
Q

Potassium reabsorption in the distal nephron occurs in what cell type?

A

alpha intercalated cells

30
Q

By what mechanism do alpha intercalated cells reabsorb potassium?

A

via hydrogen-potassium exchange at apical membrane

Potassium diffuses across basolateral membrane

31
Q

What percent of calcium store is in the ECF?

A

0.1%

32
Q

Of the 2.5 mmol/L of plasma calcium, what percent is ionized and biologically active?

What percent is bound to proteins?

What percent is complexed to anions?

A

50% active

40% protein bound

10% complexed

33
Q

What percent of plasma calcium is filtered, and why?

A

60% filtered because 40% is bound to protein

34
Q

Calcium reabsorption in the nephron occurs everywhere except…

A

the descending limb of LOH

35
Q

What percent of filtered calcium ends up in the urine?

A

1%

36
Q

Rank the sites of calcium reabsorption from greatest to least.

A

PT > Thick Ascending > DT > CD

37
Q

What percent of calcium is reabsorbed at the proximal tubule?

A

67%

38
Q

What percent of calcium is reabsorbed in the thick ascending limb?

A

25%

39
Q

What percent of calcium is reabsorbed in the dT?

A

5-10%

40
Q

What percent of calcium is reabsorbed in the collecting duct?

A

< 5%

41
Q

What decreases the reabsorption of calcium in the thick ascending limb?

A

Furosemide

42
Q

What increases the reabsorption of calcium in the distal tubule?

A

thiazide diuretics

43
Q

Name this site of calcium reabsorption:

Passive

coupled/directly related to sodium uptake

Reabsorbed via paracellular route

A

Proximal tubule

44
Q

In the PT, when sodium uptake is high, calcium uptake will be _______

A

proportionally increased

45
Q

Name this site of calcium reabsorption:

Reabsorption driven by positive lumen potential

enters via paracellular pathway

loop diuretics interfere with calcium reabsorption

A

Thick ascending limb

46
Q

What is responsible for generating the positive lumen potential that drives calcium reabsorption in the thick ascending limb of LOH?

A

Diffusion of potassium back into lumen after transport by NKCC2

47
Q

Name this site of calcium reabsorption:

enters via calcium channels across the apical membrane

Crosses basolateral membrane via calcium ATPase and sodium-calcium exchange

Reabsorption stimulated by PTH (cAMP mediated)

A

Distal tubule

48
Q

By what mechanism do thiazide diuretics increase calcium reabsorption?

A

decreases of ICF sodium increase the inward activity of the sodium-calcium exchanger

sodium pumped in, calcium pumped out

49
Q

Sodium and calcium in the distal tubule have what relationship?

A

inverse due to sodium-calcium exchanger

50
Q

What percent of plasma PO4 is bound?

A

10%

51
Q

What role does PO4 have in the urine?

A

acts as a buffer

52
Q

What percent of PO4 is filterable at the glomerulus?

A

90-95%

53
Q

What percent of filtered PO4 is reabsorbed and where?

A

85% reabsorbed in convoluted or straight proximal tubule

54
Q

What percent of filtered PO4 ends up excreted?

A

15%

55
Q

Increases in what hormone will decrease PT potassium reabsorption and therefore increase excretion?

A

PTH

56
Q

What relationship does PO4 have with calcium in the presence of PTH?

A

inverse relationship.

increased PTH = Decreased PO4 reabsorption, increased calcium reabsorption

Physiology II (28 decks)

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