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Physiology Exam III Material > Renal Regulation of Ion concentrations > Flashcards

Renal Regulation of Ion concentrations Flashcards

1
Q

extracellular potassium is normally precisely regulated at

A

4.2 mEq/L (+0.3 mEq/L)

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2
Q

an extracellular potassium increase of __ to __ can lead to cardiac arrhythmias and higher can lead to

A

3 to 4 mEq/L. cardiac arrest or fibrillation

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3
Q

Extracellular fluid contains ___ % of total body potassium

A

2%

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4
Q

intake of potassium form a single meal can be as high as

A

50 mEq

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5
Q

____ must adjust potassium excretion rapidly and precisely in response to wide variations in intake

A

kidneys (mainly involves distal and collecting tubules)

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6
Q

What is mainly involved in kidneys adjusting potassium excretion

A

distal and collecting tubules

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7
Q

What is the normal intracellular concentration of potassium ion

A

140 mEQ/L

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8
Q

Total amount of extracellular potassium

A

4.2 mEq/L x 14 L = 59 mEq

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9
Q

Total amount of intracellular potassium

A

140 mEq/L x 28 L= 3920 mEq

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10
Q

Major factors responsible for potassium excretion

A
  • Direct influence on distal renal tubules and collecting ducts via increase in extracellular potassium ion concentration
  • Effect of aldosterone secretion on potassium excretion
    • increase in extracellular potassium stimulates increase in aldosterone secretion
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11
Q

An increase in extracellular potassium stimulates a _____ in aldosterone secretion

A

increase

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12
Q

potassium daily intake is equal to

A

100 mEq/day

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13
Q

Potassium daily output in urine and feces

A

urine- 92 mEq/day

Feces- 8 mEq/Day

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14
Q

Sites of potassium reabsorption

A
  • proximal tubule

- Ascending limb of Henle

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15
Q

Sites for the secretion of potassium in the nephron

A
  • Late tubule

- Collecting duct

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16
Q

potassium secretion by principle cells is stimulated by

A

potassium concentration and aldosterone

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17
Q

Treatment of hypertension with Beta-Adrenergic receptor blockers, such as propranolol, causes potassium to

A

-move out of the cells and creates a tendency toward hyperkalemia

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18
Q

What __ % of filtered potassium is reabsorbed in the proximal tubule

A

65%

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19
Q

What % of filtered potassium is reabsorbed in the loop of Henle

A

25-30% (especially in the thick ascending part where potassium is actively co-transported along with sodium and chloride)

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20
Q

Cells in the late distal and cortical collecting tubules that secrete potassium are called

A

principle cells

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21
Q

explain how principle cells excrete potassium into tubular lumen

A

Sodium-potassium ATPase on the basolateral side exchanges potassium for sodium. The increase in potassium inside the cell leaves to a passive diffusion of potassium from the interior of the cell into the tubular fluid

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22
Q

How does aldosterone effect extracellular potassium levels

A

Aldosterone stimulates active reabsorption of sodium ions by the principle cells of the late distal tubules and collecting ducts

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23
Q

as aldosterone levels and extracellular K+ levels increase what happens to the urinary potassium excretion

A

it increases

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24
Q

small changes in serum potassium concentration cause ____ changes in aldosterone by adrenals

A

large

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25
Q

what is the direct and indirect way that high potassium intake raises potassium excretion

A
  • Direct influence on kidneys via high potassium concentration
  • Indirect via aldosterone secretion
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26
Q

high potassium intake _____ the potassium secretion rate even at low tubular flow rates

A

greatly increases

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27
Q

A rise in distal tubular flow rate does what to potassium secretion

A

stimulates potassium secretion

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28
Q

explain how high sodium intake has a counterbalance effect on potassium secretion

A

High sodium intake leads to a decreased aldosterone secretion and thus decrease potassium secretion. But increased sodium intake also leads to increase in GFR and Decrease in proximal tubular Na reabsorption, which leads to increased distal tubular flow and increased potassium secretion.

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29
Q

A High sodium diet leads to ____ change in potassium excretion

A

little.

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30
Q

Explain how low sodium intake has a counterbalance effect on potassium secretion

A

-increase in aldosterone—> increase potassium secretion
also decreases GFR and distal tubular flow rate thus decreased potassium excretion
between the two there is now change in potassium secretion

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31
Q

about 50% of total plasma calcium is in the ___ form

A

ionized form (ionized has biological activity at cell membraes)

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32
Q

Acidosis has what changes on calcium binding

A

less calcium is bound to the plasma proteins

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33
Q

Alkalosis has what changes on calcium binding

A

more calcium is bound to the plasma proteins

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34
Q

A large amount of calcium is excretion occurs in the

A

feces; therefore, GI tract is important in calcium homeostasis

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35
Q

Almost all calcium in the body is stored in

A

the bones

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36
Q

____ is one of the most important regulators of bone uptake and release of calcium

A

PTH (parathyroid hormone)

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37
Q

Parathyroid glands are directly stimulated by

A

low calcium levels

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38
Q

Low calcium levels increase the secretion of

A

PTH (parathyroid hormone)

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39
Q

Parathyroid hormone effects

A
  • stimulates bone reabsorption
  • stimulates activation of Vitamin D
  • Indirectly increases tubular calcium reabsorption
40
Q

About __% of filtered calcium is reabsorbed in the proximal tubule.

A

99%

41
Q

What percentage of filtered calcium is reabsorbed in the proximal tubule through the paracellular route

A

65%

42
Q

What percentage of filtered calcium is reabsorbed in the proximal tubule through the transcellular route

A

20%

43
Q

How is calcium reabsorbed in the proximal tubule by the transcellular route

A
  • electrochemical gradient

- Basolateral calcium-ATPase and sodium-calcium counter-transport

44
Q

Calcium reabsorption in the loop of Henle is restricted to the

A

thick ascending limb

45
Q

of the calcium reabsorbed in the thick ascending loop of Henle what percent is through the paracellular route

A

50% (passive diffusion and slight positive charge of tubular lumen)

46
Q

of the calcium reabsorbed in the thick ascending loop of Henle what percent is through the transcellular route and is stimulated by

A

50% stimulated by PTH (parathyroid hormone)

47
Q

Calcium reabsorption in the distal tubule is almost entirely via _____ transport in the ____ membrane

A

active transport (calcium-ATPase pump) in the basolateral membrane

48
Q

Calcium reabsorption in the distal tubule is stimulated by

A

PTH (parathyroid hormone)

49
Q

Factors that regulate tubular calcium reabsorption

A
  • PTH
  • plasma concentration of calcium
  • metabolic acidosis
50
Q

Factors that increase calcium excretion

A
  • decrease in PTH
  • Increase in extracellular fluid volume
  • increase in blood pressure
  • decrease in plasma phosphate
  • Metabolic acidosis
51
Q

Factors that decrease calcium excretion

A
  • Increase in PTH
  • Decrease in extracellular fluid volume
  • decrease in blood pressure
  • increase in plasma phosphate
  • metabolic alkalosis
  • Vitamin D3
52
Q

compensatory responses to decrease plasma ionized calcium concentration is mediated by

A

PTH

53
Q

Vitamin D3 is activated by

A

increase in PTH

54
Q

Vitamin D3 functions in

A

increasing intestinal calcium reabsorption

55
Q

who does the calcium exhanger in the proximal tubular cells work

A

3 sodium in and 1 calcium out (into the renal interstitial fluid)

56
Q

phosphate transport maximum for reabsorption equals

A

0.1 mM/min

57
Q

phosphate excretion by the kidneys is controlled primarily by an

A

overflow mechanism

58
Q

phosphate normally begins to spill into the urine when its concentration in the extracellular fluid rises above a threshold of about

A

0.8 mM/L

59
Q

When less than .1mmol of phosphate is present in the glomerular filtrate than

A

essentially all the filtered phosphate is reabsorbed

60
Q

When more than .1 mmol of phosphate is present in the glomerular filtrate than

A

the excess (over .1mmol) is secreted

61
Q

____ % of phosphate is reabsorbed in the proximal tubule via what pathway

A

75%-80%, transcellular

62
Q

___% fo phosphate is reabsorbed in the distal tubule

A

10%

63
Q

how does PTH effect phosphate concentrations

A
  • PTH promotes bone reabsorption and thus an increase in phosphate in the extracellular fluid-
  • PTH decreases transport maximum for phosphate by renal tubules —> greater loss of phosphate in urine
64
Q

Whenever plasma PTH is ____ , tubular reabsorption is decreased and more phosphate is excreted.

A

increased

65
Q

extracellular fluid potassium concentration normally is maintained at

A

4.2 (plus or minus 0.3 mEq/L)

66
Q

only ___ % of the total body potassium is in the extracellular fluid

A

2%

67
Q

____ must be able to adjust potassium excretion rapidly

A

Kidneys

68
Q

____, ____, and _____ stimulate potassium uptake by cells

A

Insulin, aldosterone, beta-adrenergic stimulation (epinephrine)

69
Q

What is conn’s syndrome. What does it lead to

A

increased secretion of aldosterone. Leads to hypokalemia

70
Q

What is Addison’s disease?

A

is adrenal insufficiency

decreased levels of aldosterone leads to hyperkalemia

71
Q

Aldosterone stimulates active reabsorption of Na+ by _____ cells via sodium-potassium-ATPase pump

A

principle cells

72
Q

Can beta-adrenergic receptor blockers lead to hyperkalemia

A

yes

73
Q

____ potassium intake stimulates aldosterone secretion

A

increase

74
Q

metabolic acidosis has what effect on extracellular potassium concentration

A

increases extracellular potassium concentration

75
Q

metabolic alkalosis has what effect on extracellular potassium concentration

A

decreases extracellular potassium concentration

76
Q

Cell lysis, strenuous exercise, and increased extracellular fluid osmolarity have what effect on extracellular potassium concentration

A

hyperkalemia

77
Q

increased H+ concentration —-> reduction in activity of ________ pump —-> decrease in cellular uptake of potassium

A

Na+-K+ ATPase pump

78
Q

What is the rate of potassium filtration

A

Normal= 180 L/day x 4.2 mEq/L= 756 mEq/day

79
Q

what is the rate of potassium reabsorption in the proximal tubule (%)

A

65%

80
Q

What percent of potassium is reabsorbed in the loop of Henle

A

25-30%

81
Q

90% of the cells in the late distal tubule and cortical collecting tubules are

A

principle cells

82
Q

Principle cells in the late distal tubule and cortical collecting tubules have what function

A

Secrete potassium into tubular fluid

  • have Na+-K+-ATPase pump in basolateral membrane
  • passive diffusion of K+ into tubular lumen
83
Q

What factors stimulate potassium secretion in the principle cells

A
  • increase in extracellular fluid potassium concentration
    • stimulates Na+-K+-ATPase
    • increase potassium gradient from ECF to cellular fluid
    • stimulates aldosterone secretion
  • increase aldosterone
  • tubular flow rate
84
Q

What are the controls of Potassium secretion

A
  • activity of Na+-K+ ATPase pump
  • electrochemical gradients
  • permeability of luminal membrane
85
Q

What is the role of intercalated cells

A
  • Reabsorb K+ during K+ depletion:
    • possibly through a H+-K+-ATPase
    • secrete H+ into tubular lumen
86
Q

Most of the potassium reabsorption occurs at

A

proximal convoluted tubule

87
Q

what type of cells play a major role in the secretion of potassium

A

principle cells

88
Q

Approximately how much of the body’s supply of calcium is stored in the bone

A

99%

89
Q

how much of the filtered calcium is secreted by the kidneys

A

1%

90
Q

What cells reabsorb potassium during potassium depletions

A

intercalated cells

91
Q

a high potassium intake would have what effect on potassium excretion associated with increased renal tubular flow rate

A

-potassium excretion would increase with an increase in tubular flow rate

92
Q

which of the following describes a valid change in potassium distribution due to an acid-base abnormality?
A.) metabolic acidosis decreases extracellular K+ concentration
B.) Metabolic alkalosis increases extracellular K+ concentration
C.) metabolic acidosis increases extracellular K+ concentration
D. both A and B are valid

A

C.) Metabolic acidosis increases extracellular K+ concentration

93
Q

At high levels of angiotensin II greater _______ in arterial pressure are necessary to ______ sodium excretion

A

increases, increase

94
Q

at reduced angiotensin II levels, normal levels of sodium can be maintained at ______ arterial pressures

A

reduced

95
Q

Blood volume ___________ in normal range of daily fluid intakes

A

remains relatively normal

Physiology Exam III Material (13 decks)

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