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Physiology I Final > Lecture 18 Renal Regulation of Ions > Flashcards

Lecture 18 Renal Regulation of Ions Flashcards

1
Q

Normal intracellular concentration of potassium ion is:

A

140 mEQ/L

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2
Q

Normal extracellular concentration of potassium ions is:

A

4.2 mEQ/L

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3
Q

What is the clinical significance of excess extracellular potassium?

A

Extracellular potassium is regulated precisely at 4.2 mEq/L. An increase can lead to cardiac arrhythmia, even higher can lead to cardiac arrest or fibrillation.

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4
Q

Why must the kidneys be able to rapidly adjust extracellular potassium concentration?

A

We have a wide variety of intake for potassium. The kidneys are the only method of adjusting for that.

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5
Q

What is the overall effect of aldosterone secretion on potassium excretion?

A

Increase in extracellular potassium stimulates increase in aldosterone secretion

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6
Q

What part of the renal tubule is responsible for potassium reabsorption and what part is responsible for potassium secretion?

A

the DISTAL renal tubules and collecting ducts will be stimulated to EXCRETE excess potassium. (aldosterone) is the key

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7
Q

Describe the mechanism by which principal cells secrete potassium.

A

.Potassium secretion and Sodium reabsorption done by principal cells. The potassium secretion is stimulated by the potassium concentration and aldosterone.

On the apical side: Na+/K+ ATP exchanger. Lumen side: ENaC brings Sodium in, and Potassium goes out.

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8
Q

What factors stimulate principal cells to secrete potassium?

A

High potassium intake raises potassium excretion. Direct influence on kidneys via high K concentration, Indirect via aldosterone secretion. Very small changes in potassium concentration will cause a LARGE change in aldosterone secretion by adrenals.

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9
Q

Describe the relationship between tubular flow rate and potassium secretion.

A

High potassium intake greatly increases the potassium secretion rate, even at low tubular flow rates.

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10
Q

Describe and explain why high sodium intake has little effect on potassium excretion.

A

Increased sodium intake causes decreased aldosterone secretion. THEREFORE it will cause Cortical collecting ducts to KEEP the Potassium. This is counteracted by: Increase in sodium causing increased GFR and Lowered Sodium absorption in the proximal tubule … this will cause the distal tubular flow rate to increase, but also increase K+ secretion in the cortical collecting ducts, and therefore the K+ excretion will be unchanged!

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11
Q

What is the overall effect of aldosterone secretion on potassium excretion?

A

Potassium secretion by principal cells is stimulated by potassium concentration and aldosterone.

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12
Q

How does plasma pH effect the amount of plasma calcium bound to plasma proteins?

A

Acidosis: less calcium is bound to the plasma proteins
Alkalosis: More calcium is bound to the plasma proteins

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13
Q

List the effects of PTH

A

PTH:
Stimulates bone reabsorption
Stimulates Activation of Vit. D
Indirectly increases tubular calcium reabsorption.

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14
Q

How much filtered Calcium is reabsorbed?

A

99% of filtered calcium is reabsorbed: 65% in proximal tubule.

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15
Q

Where in the kidney tubule does calcium reabsorption take place?

A

65% of it happens in proximal tubule via paracellular route.
20% in the proximal tubule via transcellular route. using Electrochemical gradient and Basolateral calcium-ATPase and Sodium-Calcium Counter transporter.

Calcium Reabsorption is restricted to thick ascending limb: 50% through paracellular route
…passive diffusion and slight positive charge of tubular lumen.

50% via transcellular route stimulated by PTH

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16
Q

List the factors that decrease calcium reabsorption.

A

Increased Levels of PTH
Plasma concentration of phosphate
Metabolic acidosis

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17
Q

What effects do insulin and catecholamines have on extracellular potassium levels?

A

Epinephrine: Stimulates potassium uptake by cells. If you take a Beta-adrenergic receptor blocker: Hyperkalemia

18
Q

What are the relationships of Conn’s syndrome and Addison’s disease to aldosterone secretion and potassium levels?

A

Hypokalemia: CONN’S Syndrome
Excess secretion of aldosterone

Hyperkalemia: ADDISON’S Disease
Deficiency in aldosterone

19
Q

What effects do metabolic acidosis have on EC Potassium Concentration?

A

Increases Extracellular K+ concentration

20
Q

What effects do metabolic alkalosis have on EC Potassium concentration ?

A

Increase in EC K+ Concentration, and increase in H+ concentration, leads to a reduction in activity of Sodium/Potassium ATPASE pump and that will lead to a decrease in cellular uptake of K+

21
Q

What effects do cell lysis have on EC Potassium concentration ?

A

Hyperkalemia

22
Q

What effects do strenuous exercise have on EC Potassium concentration ?

A

Hyperkalemia

23
Q

What effects do increased extracellular laid osmolarity have on EC Potassium concentration ?

A

Hyperkalemia

24
Q

Describe the role of intercalated cells in controlling potassium levels.

A

Reabsorb K+ during K+ depletion:

Possibly through a H+/K+ATPase pump, secrete H+ into tubular lumen

25
Q

Increase in extracellular potassium stimulates what?

A

increase in aldosterone secretion from Adrenals.

26
Q

Increased levels of PTH, plasma concentration of phosphate, and metabolic acidosis:

A

decrease calcium excretion

27
Q

what would promote a decrease calcium excretion?

A

increased levels of PTH
increased plasma phosphate
metabolic acidosis.

28
Q

Insulin and aldosterone do what?

A

stimulate the uptake of potassium by cells?

29
Q

What two hormones would promote the uptake of potassium by a cell?

A

Insulin and aldosterone

30
Q

Conn’s Syndrome

A

Hypokalemia from excess secretion of aldosterone

31
Q

Addison’s disease

A

Hyperkalemia from a deficiency in aldosterone secretion

32
Q

Almost all of the filtered calcium…

A

is reabsorbed by the kidney.

33
Q

How much filtered calcium is excreted by the kidneys?

a. 1%
b. 47%
c. 78%
d. 99%

A

A. 1%

34
Q

% Calcium supply is stored in the bones:

a. 1%
b. 47%
c. 78%
d. 99%

A

D. 99%

35
Q 
Major role in stimulating potassium excretion by kidney tubules:
a. aldosterone
b. Angiotensin II
c. Sodium ion
D. PTH
A

A. Aldosterone.

36
Q 
Which cells play a major role in the secretion of K+?
A. intercalated
B. principal cells
C. chief
D. Podocytes
A

B. Principal Cells

37
Q 
Which cells play a major role in the reabsorption of K+?
A. intercalated
B. principal cells
C. chief
D. Podocytes
A

A. Intercalated

38
Q 
Most K+ reabsorption occurs at which of the following sites:
A.  Ascending LOH
B. DCT
C. PCT
D. Collecting Duct
A

C. Proximal Convoluted Tubule

39
Q

A blockage of the aldosterone system would ultimately do what?

A

impair regulation of potassium concentration

40
Q

What effects do metabolic alkalosis have on EC Potassium Concentration?

A

Decrease in extracellular K+ concentration

Physiology I Final (9 decks)

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