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Renal-1 > Regulation of K+ Balance + Intro DSA > Flashcards

Regulation of K+ Balance + Intro DSA Flashcards

1
Q

How does the cardiac conduction system respond to hyperkalemia?

A

the opposite of other cells!

hyperkalemia –> hyperpolarizes membrane –> high T waves

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2
Q

What are the most important factors that stimulate potassium secretion?

A
  1. Increased K in ECF
  2. Aldosterone
  3. Increased tubular flow rate
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3
Q

What is pseudohyperkalemia?

A

artificially high plasma K levels due to lysis of RBCs while blood is drawn

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4
Q

How does hyperkalemia affect membrane potential?

A

hypopolarizes the cell –> easier to depolarize and make action potential

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5
Q

How does hypercalcemia affect membrane potential?

A

increases threshold –> cells are less excitable

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6
Q

What is alkalemia?

A

physiologically high blood pH

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7
Q

How does decreased flow rate affect K+?

A

K+ concentration builds up earlier in tubule –> concentration gradient decreased –> K+ secretion slows

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8
Q

What are the most important factors that stimulate K reabsorption?

A
  1. K+ deficiency, low K+ diet, hypokalemia
  2. K+ loss through severe diarrhea
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9
Q

Where is K+ found throughout the body?

A

98% intracellular

  • 80% muscle cells
  • 20% other cells

2% extracellular

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10
Q

How do beta-catecholamines affect K?

A

enhance cell uptake

+ Na-K-ATPase via + cAMP

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11
Q

How does increased flow rate affect K+?

A

increased flow rate dilutes K+ secreted into lumen –> increases K+ concentration gradient bc K+ is washed away –> delivers more Na+ to DT for reabsorption –> K+ secretion is promoted

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12
Q

How does aldosterone affect serum K+ concentration?

A

lowers serum K

renal: increases K+ excretion
extrarenal: increases K+ secretion into intestinal fluids and saliva; enhances acid excretion via production of systemic alkalosis

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13
Q

What is the normal dietary intake of calcium for an adult?

A

1000 mg/day

absorption best at <500 mg

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14
Q

How does acute acidosis affect K+

A

decreased activity of Na-K-ATPase pump

decreased K+ brought into cells from IF

decreased K+ secretion

end result = hyperkalemia

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15
Q

What occurs to K+ in the late DT and cortical CD?

A

secreted or reabsorbed according to the needs of the body

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16
Q

Where is phophate distrubuted in the body?

A

85% bone

14% cells

1% serum

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17
Q

How does the heart respond to hypokalemia?

A

the opposite of other cells

hypokalemia –> hypopolarized –> low T wave and tachycardia

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18
Q

Where is magnesium distributed in the body?

A

50% in bone

49% in ICF

1% in ECF

19
Q

How does chronic acidosis affect K+?

A

chronic acidosis decreases reabsorption of water and solutes by PT by inhibiting NaKATPase –> increases tubular flow –> RAAS stimulated due to lack of water reabsorption –> ends up increasing K+ secretion

20
Q

What is normal total serum Mg?

Free?

A

total = 1.8 mEq/L

Free = 0.8 - 1.0 mEq/L

21
Q

How does cell damage affect K?

A

impaired cell uptake

release of intracellular contents

22
Q

How does increased NaCl reabsorption upstream affect K+ secretion downstream?

A

decreases it

bc less Na delivery to CNT and CCD –> decreases Lumen-negative potential difference

23
Q

What happens to K+ in Beta intercalated cells?

A

H+ /K+ antiporter on basolateral surface pulls in K+ from IF –> K+ flows down gradient into tubular lumen = K+ secreted

BS = beta secretes

24
Q

How does hyperosmolality affect K?

A

enhanced cell eflux H2O goes out of cells to balance –> K+ concentration in cells increases –> K+ goes out of cells down its gradient

25
Q

What is the recommended phosphorus intake?

How much is actually absorbed?

A

1500 mg dietary intake required

1100 mg absorbed

200 mg secreted into gut

~net 900 mg phosphorus absorbed per day

26
Q

What is K+ resorption like in the proximal tubule (in general)?

A

similar to Na+ resorption

plays an indirect role in regulation of K+ balance via NaCl reabsorption –> affects distal tubular flow –> impacts K+ later on

27
Q

What happens to K+ in principal cells of the collecting duct?

A

Na-K-ATPase pump on basolateral side pulls K in from the IF –> K exits and is secreted into tubular lumen via BK and ROMK ENaC pulls in Na from lumen and is target of aldosterone

28
Q

What happens to K+ in alpha-intercalated cells?

A

Alpha reAbsorbs K

H+/K+ antiporter on apical surface pulls in K+ –> goes down gradient and is reabsorbed

29
Q

What is the equation for filtered load?

A

GFR x plasma concentration x %filterability

30
Q

How does acute alkalosis affect K+?

A

increased activity of Na-K-ATPase

increased K brought into cells from IF

Increased K+ secretion

end result = hypokalemia (K+ is lo)

31
Q

What are the 4 steps of LoH transport and recycling of K+?

A
  1. K+ secreted into cortical collecting duct
  2. K+ reabsorbed by OMCD and IMCD
  3. K+ floats in interstitium
  4. K+ secreted into Late PT/descending thin limbs of LoH
32
Q

Via what mechanism is K+ reabsorbed in the PT?

A

paracellularly

33
Q

How does hypocalcemia affect membrane potential?

A

decreases threshold –> cells are more excitable

hypocalcemic tetany/spasticity

34
Q

How do alpha catecholamines affect K?

A

impaired cell uptake

  • Na-K-ATPase via - cAMP
35
Q

How does epinephrine affect serum K+ concentrations?

A

lowers serum K increases uptake into extrarenal cells stimulates K excretion by the kidney

(differing response for alpha vs beta receptors)

36
Q

How do high sodium and flow rate relate?

A

High sodium or decreased aldosterone inhibits K+ secretion

High flow rate increases K+ secretion

counteract/balance each other out

37
Q

How does hypokalemia affect membrane potential?

A

hyperpolarizes cell – harder to make action potential

38
Q

What is alkalosis?

A

decrease in H+ ion concentration in the ECF

acute process

39
Q

How does anion deliver affect K+?

A

increases K+ secretion

40
Q

How does strenuous exercise affect K?

A

enhanced cell efflux

+ alpha catecholamines

41
Q

What is the goal of K+ recycling?

A

increase presence of medullary K+ –> decreases NKCC reabsorption by TAL –> enhanced Na delivery to distal tubule –> stimulates Na reabsorption and K+ secretion = helps you excrete more K+ during dietary load!!!

42
Q

What is the normal range of plasma K+ concentration?

A

3.5 - 5.0 mEq/L

43
Q

How does Insulin affect serum K+ concentration?

A

lowers serum K stimulates Na-K-ATPase –> flux of K+ into cells and efflux of Na+ out of cells

*insulin and glucose administration can treat hyperkalemia

44
Q

How is K+ reabsorption driven in the PT?

A

In early PT, Na reabsorbed primarily w/ HCO3- Cl- gets left behind –> - charges build up (TEPD) –> Cl- is repelled and reabsorbed –> water dragged along –> positive TEPD builds up as Cl- reabsorbed –> positive TEPD repels K+ –> K+ reabsorbed PARACELLULARLY

Renal-1 (14 decks)

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