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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
What two factors cause an increase in aldosterone secretion?
increased AT II Increased plasma potassium
26
A low potassium diet causes what homeostatic response?
decreased excretion
27
In a low potassium diet, what percent of filtered potassium is reabsorbed and where?
87% reabsorbed in the PT and LOH
28
The PT and LOH reabsorb 87% of filtered potassium in low potassium conditions. Where is the remaining potassium reabosorbed?
distal nephron (DT/CD)
29
Potassium reabsorption in the distal nephron occurs in what cell type?
alpha intercalated cells
30
By what mechanism do alpha intercalated cells reabsorb potassium?
via hydrogen-potassium exchange at apical membrane Potassium diffuses across basolateral membrane
31
What percent of calcium store is in the ECF?
0.1%
32
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?
50% active 40% protein bound 10% complexed
33
What percent of plasma calcium is filtered, and why?
60% filtered because 40% is bound to protein
34
Calcium reabsorption in the nephron occurs everywhere except...
the descending limb of LOH
35
What percent of filtered calcium ends up in the urine?
1%
36
Rank the sites of calcium reabsorption from greatest to least.
PT > Thick Ascending > DT > CD
37
What percent of calcium is reabsorbed at the proximal tubule?
67%
38
What percent of calcium is reabsorbed in the thick ascending limb?
25%
39
What percent of calcium is reabsorbed in the dT?
5-10%
40
What percent of calcium is reabsorbed in the collecting duct?
< 5%
41
What decreases the reabsorption of calcium in the thick ascending limb?
Furosemide
42
What increases the reabsorption of calcium in the distal tubule?
thiazide diuretics
43
Name this site of calcium reabsorption: Passive coupled/directly related to sodium uptake Reabsorbed via paracellular route
Proximal tubule
44
In the PT, when sodium uptake is high, calcium uptake will be _______
proportionally increased
45
Name this site of calcium reabsorption: Reabsorption driven by positive lumen potential enters via paracellular pathway loop diuretics interfere with calcium reabsorption
Thick ascending limb
46
What is responsible for generating the positive lumen potential that drives calcium reabsorption in the thick ascending limb of LOH?
Diffusion of potassium back into lumen after transport by NKCC2
47
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)
Distal tubule
48
By what mechanism do thiazide diuretics increase calcium reabsorption?
decreases of ICF sodium increase the inward activity of the sodium-calcium exchanger sodium pumped in, calcium pumped out
49
Sodium and calcium in the distal tubule have what relationship?
inverse due to sodium-calcium exchanger
50
What percent of plasma PO4 is bound?
10%
51
What role does PO4 have in the urine?
acts as a buffer
52
What percent of PO4 is filterable at the glomerulus?
90-95%
53
What percent of filtered PO4 is reabsorbed and where?
85% reabsorbed in convoluted or straight proximal tubule
54
What percent of filtered PO4 ends up excreted?
15%
55
Increases in what hormone will decrease PT potassium reabsorption and therefore increase excretion?
PTH
56
What relationship does PO4 have with calcium in the presence of PTH?
inverse relationship. increased PTH = Decreased PO4 reabsorption, increased calcium reabsorption

Physiology II (28 decks)

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