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Unit 7: Physiology > Regulation of plasma K+ > Flashcards

Regulation of plasma K+ Flashcards

1
Q

What percent of K+ is intracellular and why?

A

98% due to Na/K ATPase

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2
Q

What range is K+ tightly regulated in plasma?

A

3.5-5 mM

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3
Q

Is K+ a major determinant of voltage difference in excitable or unexcitable cells?

A

both

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4
Q 
In hyperkalemia:
depolarization or hyperpolarization?
hyperexcitability or hypoexcitability?
how does it affect the heart?
metabolic acidosis or alkalosis?
A

depolarized
hyperexcitability
ventricular arrythmia and fibrillation
metabolic acidosis

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5
Q 
In hyperkalemia:
depolarization or hyperpolarization?
hyperexcitability or hypoexcitability?
how does it affect the heart?
metabolic acidosis or alkalosis?
A

hyperpolarization
hypoexcitability
arrythmias - bradycardia
metabolic alkalosis

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6
Q

How is k+ balanced externally?

A

renal and fecal removal of k+ from the body
amout of K+ consumed must equal amount excreted

-kidney is main regulator

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7
Q

What is the equation for the renal handling of K?

A

excreted = filtered-reabsorbed+ secreted

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8
Q

What is the main regulator of K+ internally?

A

NaKATPase

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9
Q

What organ is most K+ located in?

A

muscle

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10
Q

What is the bodie’s first line of defense against hyperkalemia?

A

inc uptake into cells

-sequestration by Na/K ATPase

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11
Q

What three hormones promote cellular uptake of K+, and how do they do this?

A

epinephrine
aldosterone
insulin

-promote de novo synthesis of NaKATPase

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12
Q

Do RBCs respond to hormones to inc K+ uptake?

A

N0O0O they don’t have nuclei and cant make proteins

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13
Q

Are diabetics more likely to be hyperkalemic or hypokalemic?

A

hyperkalemic

-dysregulation of insulin - cant take up the extra K+

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14
Q

How does a high K+ plasma concentration affect uptake in the GI tract?

A

it DOESN’T

GI tract absorption is constitutive

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15
Q

When a high load of K+ is introduced, how do the cell’s respond? how does the kidney respond?

A

cell’s respond quick and uptake K+ rapidly

kidney’s response is more slow and eventually inc secretion and dec reabsorption

eventually excretion of K+ will occur even when there is not elevated plasma K+

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16
Q

Where is most K+ reabsorbed?

A

proximal tubule -80% at a constitutive rate

17
Q

Where is reabsorption or secretion of K+ regulated?

A

distal nephron - distal tubule and cortical collecting duct

18
Q

How much of K+ is reabsorbed at loop of henle?

A

10% - not regulated

19
Q

What percent of the filtered load is the kidney able to secrete in times of hyperkalemia?

A

10-150%

20
Q

How is the renal handling of Na different from K+

A

Na+ - no secretion occurs

-old diet’s didnt have much salt

21
Q

What occurs to K+ in the proximal tubule and by what method?

A

reabsorption

paracellular

22
Q

What drives the paracellular reabsorption of K+ in the early and late proximal tubule?

A

early: active transcellular Na+ transport drives net fluid reabsorption by osmosis

late: transepithelial voltage is positive
- driving force for K+

23
Q

how does the Na/K ATPase in the proximal tubule contribute to paracellular reabsorption of k+ ?

A

it doesn’t!

24
Q

What occurs to K+ in the thick ascending loop of henle and by what method?

A

reabsorption

transcellular and paracellular

25
Q

What drives paracellular transport in the thick ascending loop of henle?

A

lumen positive voltage difference

26
Q

What drives the transcellular reabsorption in the thick ascending loop of henle?

A

membrane specific transporters

luminal: na/k/2cl cotransporter transport these ions in
basolateral: Cl, K+ transporters and Na/K ATPase

27
Q

A small amount of K+ effluxes into the lumen through K+ channels, what does this provide a driving force for?

A

ca and Mg reabsorption

28
Q

What occurs to K+ in the distal nephron and by what method?

A

secretion or reabsorption

transcellularly

29
Q

How does transcellular k+ reabsorption in the distal nephron occur?

A

K/H ATPase

actively transports K into cell and H out

30
Q

How does transcellular K+ secretion occur in the distal nephron?

A

active transport basolaterally

passive transport luminally

31
Q

When flow rates are high in the distal nephron, how is K+ secretion affected?

A

K+ secretion is able to be much higher

-K+ is swept away as fast as it is transported out driving secretion

32
Q

What is a major complication of diuretics?

A

hyperkalemia

33
Q

In the distal nephron what is K+ secretion coupled to?

A

Na+ reabsorption

34
Q

What are the three effects of aldosterone?

A
  1. inc synthesis of Na/K ATPase
  2. inc prodution of Na and K+ channels
  3. inc production of mito enzymes
35
Q

What is the relationship btwn alkalosis, acidosis, hyperkalemia and hypokalemia?

A

alkalosis hypokalemia

acidosis hyperkalemia

needs to be delicate balance btwn H/K ATPase function

Unit 7: Physiology (19 decks)

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