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Physiology I Exam 2 > Lecture 8: Regulation of Potassium Balance > Flashcards

Lecture 8: Regulation of Potassium Balance Flashcards

1
Q

Where is most K+ located?

A

ICF

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2
Q

How is ICF K+ controlled?

A

Na+/K+ pump

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3
Q

Internal K balance

A

Distribution of K+ across cell membranes

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4
Q

External K Balance

A

Renal mechanisms to manage variations in K+ intake

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5
Q

What pump helps with internal K+ balance and with buffering when needed?

A

H+/K+ pump

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6
Q

Alkalemia is accompanied by what condition

A

Hypokalemia

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7
Q

What is the mechanism that causes Alkalemia

A

Hydrogen in blood decreases, so H+ leaves to enter ECF and K+ enters cells

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8
Q

Acidemia is accompanied by what condition

A

Hyperkalemia

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9
Q

What is the mechanism that causes acidemia?

A

Hydrogen in blood increases, so H+ enters and K+ leaves the cell exchange

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10
Q

Do acid-base disturbances always cause a K+ shift across membranes?

A

No (particularly if disturbance is respiratory acidosis or respiratory alkalosis)

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11
Q

Hyperkalemia leads to what kind of cells

A

Hyperexcitable

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12
Q

Hypokalemia leads to what in cells

A

Hyperpolarization

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13
Q

Why does hyperkalemia lead to hyperexcitable cells?

A

More potassium outside of cell and concentration of K more equal than between inside and outside. Decreased concentration gradient so less driving force for K+ to leave inside of cell –> RMP more positive/closer to threshold

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14
Q

Why does Hypokalemia lead to hyperpolarization

A

K+ shifts into cells, so have more K inside than normal. Concentration gradient increases even more, so K leaves via channels because driving force is increase, so RMP even more negative and harder to reach threshold

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15
Q

Insulin increases what pump activity

A

Na+/K+ ATPase activity

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16
Q

Insulin increases uptake of what into cells

A

K+

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17
Q

What condition does insulin prevent?

A

Hyperkalemia

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18
Q

What happens if insulin is deficient (Type 1 diabetes)?

A

Decreases K intake after meals –> Hyperkalemia

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19
Q

What are the 6 major factors that disturb internal K+ balance?

A

Catecholamines
Osmolarity
Cell lysis
Exercise
Insulin
Acid-base abnormalities

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20
Q

Beta-2 adrenergic agonists increase activity of what

A

Na+/K+ ATP (increase potassium in cell, hypokalemia)

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21
Q

Alpha-adrenergic agonist cause shift in K+ where

A

Out of cells - hyperkalemia

22
Q

Alkalemia

A

Less hydrogen in blood

23
Q

Acidemia

A

More hydrogen in blood

24
Q

How does hyperosmolarity impact internal K+ balance?

A

Water moves from ICF to ECF to increase concentration of K+ inside cells, drives diffusion of K into ECF

25
Q

How does cell lysis impact internal K+ balance?

A

Breakdown of cell membranes releases K+ from ICF

26
Q

How does exercise impact internal K+ balance?

A

Causes shift of K+ out of cells
Can result in hyperkalemia in those with renal failure, or if taking beta2 adrenergic antagonist

27
Q

K+ balance = ? + ?

A

Daily urinary excretion of K+ + dietary K+ intake

28
Q

If excretion of K+ less than intake then what kind of K balance?

A

Positive K balance

29
Q

If excretion of K+ greater than intake, then what kind of K balance?

A

Negative K balance

30
Q

Filtration/filtered load is dependent on

A

Blood K concentration

31
Q

Reabsorption is dependent on

A

Need to conserve (increases if need to conserve increases)

32
Q

Secretion is dependent on

A

If need to excrete more, increased secretion

33
Q

What part handles 67% K+ filtered?

A

PCT

34
Q

Where is K+ reabsorption relatively constant?

A

PCT and TAL

35
Q

What part reabsorbs ~20% of K+ in filtered load?

A

TAL

36
Q

What transporter is used in the TAL for K

A

Na/K/2Cl transporter

37
Q

Distal tubule and collecting ducts are responsible for

A

Fine tuning of K+ excretion

38
Q

What part of the renal tubule is K+ excretion dependent upon diet

A

CD and DT

39
Q

If there is a low K+ diet, then what happens and what cells do it

A

Reabsorption by alpha-intercalated cells

40
Q

If there is normal to high K+ diet then what happens and what cells do it

A

Secretion by principal cells

41
Q

What pump controls K+ reabsorption by alpha intercalated cells on luminal membrane?

A

H+/K+ ATPase

42
Q

What pump controls K+ reabsorption by alpha intercalated cells on basolateral membrane?

A

K+ channel

43
Q

How do principal cells move K+ from blood to lumen of tubule (what transporter)

A

Na/K ATPase

44
Q

Magnitude of K+ secretion is determined by what

A

Size of electrochemical gradient for K across the luminal membrane (ie how much K is entering cells?)

45
Q

What factors influence magnitude of secretion of K?

A

Dietary K
Presence of aldosterone
Acid-base disturbances
Alkalosis
Acidosis

46
Q

What does dietary K+ do to influence magnitude of secretion of K+? (High and low)

A

High: Causes K+ to enter principal cells, increases ICF K+ concentration, driving force for K+ secretion
Low: K+ decreases K+ in principal cells

47
Q

How does presence aldosterone affect K+ secretion?

A

K+ will be secreted more by principal cells (because aldosterone increases Na+ reabsorption)

48
Q

Increase potassium in cells is driving force for

A

Secretion

49
Q

How does alkalosis impact secretion of K+

A

Less H+ in ECF, H+ leaves cells, K+ enters cells, driving force for secretion

50
Q

How does acidosis impact secretion of K+

A

Usually decreases K+ secretion (hyperkalemia)
More H+ in ECF, so H+ enters cells
K+ leaves, decreases K+ in cells, so less secreted

Physiology I Exam 2 (12 decks)

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