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Physiology I > Lecture 18 - Renal Regulation Of [ion] > Flashcards

Lecture 18 - Renal Regulation Of [ion] Flashcards

1
Q

The normal [K]ecf is _______.

A. 142 mEq/L ( 0.3mEq/L)
B. 4.2 mEq/L ( 0.3mEq/L)
C. 150 mEq/L
D. 5 mEq/L

A

B. 4.2 mEq/L ( 0.3mEq/L)

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2
Q

ECF contains approximately what % of body K?

A. 1%
B. 5%
C. 25%
D. 79%

A

A. 1%

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3
Q

An increase in ECF [K] of _____ may lead to the development of cardiac arrhythmia.

A

3-4 mEq/L

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4
Q

Normal ICF [K] is _______.

A. 140 mEq/L ( 0.3mEq/L)
B. 4.2 mEq/L ( 0.3mEq/L)
C. 150 mEq/L
D. 5 mEq/L

A

A. 140 mEq/L ( 0.3mEq/L)

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5
Q

ECF potassium is directly controlled in what two portions of the nephron?

A

DCT and collecting ducts

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6
Q

Aldosterone is a stimulator/inhibitor of potassium secretion

A

stimulator (increased aldosterone increases potassium loss)

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7
Q

Potassium reabsorption occurs in the:

A. PCT and late DCT
B. Ascending limb of LoH
C. Collecting duct and PCT
D. PCT and ascending LOH

A

D. PCT and ascending LoH

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8
Q

Potassium secretion/sodium reabsorption occurs via the ____ in principal cells.

A

Na/K ATPase

Na+ is reabsorbed; K+ is secreted

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9
Q

K+ flow through ____ on the apical membrane

A

K+ channel

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10
Q

High K+ plasma produces an ____ in aldosterone, as well as direct K+ secretion in the ______.

A

Increase

cortical collecting tubules

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11
Q

Approximately 50% of Ca2+ is found ______ proteins.

A

bound to transport

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12
Q

Changes to ___ will affect the binding of Ca2+ to transport proteins

A. Cell size
B. Blood volume
C. Body temp
D. pH

A

D. pH (changing pH will change proteins)

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13
Q

Acidosis results in a ____ of protein bound Ca2+.

A. Decrease
B. Increase
C. No change

A

A. decrease

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14
Q

Release of _____ causes an increase in blood calcium levels.

A

PTH

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15
Q

PTH works to raise blood [Ca2+] by _____.

A

increasing bone breakdown; increasing Ca2+ absorption in the GI tract; increased Vit. D3 activation; increased tubular reabsorption (indirectly)

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16
Q

What % of Ca2+ is reabsorbed by the PCT?

A. 99%
B. 65%
C. 50%
D. 22%

A

B. 65%

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17
Q

20% of calcium is absorbed in the PCT by what routes?

A

Transcellular

  • Electrochemical gradient “pushes” Ca2+ out of the lumen
  • Basolateral Ca2+ ATPase
  • Basolateral Na+/Ca2+ exchanger
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18
Q

Calcium resorption in the loop of Henle is in the _______.

A. Thick descending
B. Thick ascending
C. Thin descending
D. Thin ascending

A

B. Thick ascending

19
Q

50% of calcium absorption in the thick ascending loop of Henle occurs by paracellular routes. The remaining 50% occurs through the transcellular route and is stimulated by ______.

A. Calcitonin
B. PTH
C. Aldosterone

A

B. PTH

20
Q

T/F: Ca2+ reabsorption occurs in all portions of the nephron.

A

False; Ca2+ reabsorption is relegated to the PCT, DCT, and thick ascending Loop of Henle

21
Q

Ca2+ reabsorption of calcium is accomplished by ____ stimulated by PTH.

A. Sodium/Calcium exchanger on the basolateral side
B. Sodium/Calcium exchanger on the apical side
C. Calcium ATPase on the basolateral side
D. Calcium ATPase on the apical side

A

C. Calcium ATPase on the basolateral side

22
Q

Phosphate excretion occurs via what mechanism?

A

overflow (Tmax=0.1mM/min)

23
Q

Resorption of phosphate occurs via a ____cellular route.

A. paracellular
B. trans

A

B. trans

24
Q

____ assists in both resorption of Ca2+ and PO4

A

PTH

25
Q

PTH causes phosphate to exceed its transport maximum; this results in _____.

A

phosphate excretion

26
Q

Of insulin, chatecholamines, and aldosterone, which produce potassium uptake?

A

all three

27
Q

Describe the mechanism of action of aldosterone in regard to potassium reabsorption

A

1) Aldosterone stimulates Na/ATPase pumps in principal cells
2) Luminal membrane permeability for K+ increases
3) Extracellular [K+] increases

28
Q

Describe the effect of metabolic acidosis on ECF [K+]

A

Acidosis (decreased pH= increased [H+]) produces changes to the proteins comprising the Na/KATPase pumps. This produces decreased re-uptake of K+ into the cells.

29
Q

Describe the effect of cell lysis on ECF [K+]

A

Increased, as lysis of cells releases large amounts of the ICF K+

30
Q

Describe the effect of metabolic alkalosis on ECF [K+]

A

Decreases extracellular K+

31
Q

Principle cells are responsible for (secretion/absorption) of K+.

A

Secretion

32
Q

Principal cells are located in what portion of the nephron?

A. DCT
B. Cortical collecting tubule
C. Medullary collecting tubule
D. DCT & Cortical collecting tubule

A

D. DCT and cortical CT

33
Q

Principle cells secrete K+ what what mechanism?

A

Na/K ATPase on the basolateral membrane

passive diffusion of K+ into tubular lumen

34
Q

Intercalated cells resorb K+ during what situation?

A. Increased ECF K+
B. Decreased ECF K+
C. Decreased tubular K+

A

B. Decreased ECF K+ (K+ depletion)

35
Q

Intercalated cells move K+ and what other ion during K+ depletion? Is this sym- or anti-port?

A

H+; anti-port (H+ is secreted)

36
Q

_____ intercalated cells secrete K+

A

Type B

37
Q

______ of the late distal and collecting tubules reabsorb K+

A

Type A intercalated cells

38
Q

By what mechanisms are internal [K] regulated?

A

Decreased ECF [K]

1) insulin - increases cellular K uptake
2) aldosterone - stimulates cellular K uptake
3) beta-adrenergic stimulation - increases cellular K uptake

Increased ECF [K]

4) acid/base disturbances - decreased pH can increase [K]ecf. The mechanism is unclear, but it’s believed to arise from decreased Na/KATPase function 2/2 acidosis*
5) cell lysis - spills out ICF potassium
6) exercise - myocytes release K with strenuous exercise
7) increased ECF Osmolarity - Complicated! Increased ECF Osmolarity promotes diffusion of water out of cells. This, in turn, raises ICF [K]. When this increase in ICF [K] occurs, K flows down its gradient into the ECF fluid.

*Remember that pumps are proteins. A change in pH affects the structure of the protein.

39
Q

Potassium excretion is primarily controlled by the _____ of the late distal and cortical collecting tubules.

A

Prinicpal (Think “Principal Potassium”)

40
Q

Outline the process of potassium excretion by the kidneys.

A

1) Increased blood [K] occurs
2) K is absorbed into renal tubule cells by basolateral Na/KATPase
3) ICF [K] is raised
4) K flows down its gradient into the tubular lumen
- occurs in prinicpal cells
- “ROMK”-renal outer medullary potassium channels
- “BK”- “Big Potassium” channels

41
Q

In severe K depletion, the ____cells act to resorb K.

A. Principle cells
B. Type A Intercalated cells
C. Type B Intercalated cells

A

B. Type A Intercalated cells

42
Q

In cases of excess potassium, the _____ act in concert with principal cells to secrete potassium.

A. Principle cells
B. Type A Intercalated cells
C. Type B Intercalated cells

A

C. Type B Intercalated cells

These are under control of aldosterone

43
Q

This hormone sees its secretion increased when ECF [K] begin to rise.

A. ADH
B. Epinephrine
C. Aldosterone
D. Erythropoietin

A

C. Aldosterone

Physiology I (28 decks)

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