Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Urinary > Potassium Control > Flashcards

Potassium Control Flashcards

0
Q

What maintains the potassium concentrations?

A

3Na-2K-ATPase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

Normal [K+] in ICF and ECF?

A 
ICF = 120-150 mmol/L
ECF = 3.5-5 mmol/L
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why is high potassium inside cells and mitochondria essential?

A 
Maintains cell volume
Regulates intracellular pH
Controls cell-enzyme function
DNA and protein synthesis
Cell growth 
Low potassium outside cells is largely responsible for the membrane potential of excitable and non-excitable cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How does hyper and hypokalaemia affect the membrane potential?

A

Hyperkalaemia: depolarises it
Hypokalaemia: hyperpolarises it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What can hypokalaemia cause?

A

Inability of kidney to form concentrated urine
Metabolic alkalosis
Enhancement of renal ammonium secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What can hyperkalaemia cause?

A

Cardiac arrhythmias

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Where in the nephron is potassium reabsorbed?

A

PCT
Thick ascending limb
DCT
Cortical collecting duct

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Where in the nephron is potassium secreted?

A

Distal tubule
Cortical collecting duct

Both by principal cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What percentage of potassium is reabsorbed in the PCT and by what processes?

A

67%

Paracellular diffusion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What percentage of potassium is reabsorbed in the thick ascending limb and by what processes?

A

20%
Na-K-2Cl transporter in apical membrane
(Driven by Na-ATPase)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How much potassium is secreted in principal cells of the DCT and cortical CD?

A

15-20%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What percentage of potassium is reabsorbed by intercalated cells of the DCT and CD? By which transporter?

A

10-12%

Hydrogen-potassium transporter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe process of secretion of potassium

A

Na-K-ATPase on basolateral membrane increases intracellular K conc and decreases Na conc
High intracellular K creates gradient for potassium secretion
Na moves from lumen to cell via ENaC making lumen negatively charged
Favourable electrochemical gradient for K+ secretion via apical K+ channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How does high ECF potassium concentration stimulate more potassium secretion?

A

Directly stimulates Na-K-ATPase and increases permeability of apical K+ channels
Also stimulates aldosterone secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How does aldosterone stimulate K secretion?

A

Increases transcription of Na-K-ATPase in basolateral membrane and ENaC/K+ channels in apical membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What luminal factors affect potassium secretion?

A

Increased distal tubular flow rate - washes away luminal K+, increasing K+ loss
Increased Na+ delivery to distal tubule - more sodium can the. Be absorbed so more potassium is lost

16
Q

How does external balance control extracellular potassium concentration?

A

Adjusts renal potassium excretion to match intake - regulates total body content
Depends on dietary intake and excretion by GI and kidneys
Responsible for long term control
Slow acting - 6-12 hours to secrete a load

17
Q

How does internal balance regulate potassium concentration?

A

Immediate effect
Shift potassium between extracellular fluid and intracellular fluid
-If ECF [K] increases - K+ into cells via Na-K-ATPase
-If ECF [K] decreases - K+ out of cells via ROMK

18
Q

What are the main things that promote potassium uptake into cells?

A

Hormones

  • insulin
  • aldosterone
  • catecholamines

Increased [K+] in ECF

Alkalosis (low ECF H+ concentration)

19
Q

What are the general factors that promote potassium shift into ECF out of cells?

A 
Low [K+] ECF
Exercise
Cell lysis
Increased plasma/ECF osmolarity
Acididosis
20
Q

How does insulin promote uptake of potassium into cells (causing hypokalaemia)

A

K+ in splanchnic blood stimulates insulin secretion by pancreas
Insulin stimulates K+ uptake by muscle and liver via increase in Na-K-ATPase

21
Q

How does aldosterone reduce ECF [K+]

A

K+ in blood stimulates aldosterone secretion
Stimulates Na-K-ATPase
Stimulates K+ secretion in kidneys

22
Q

How do catecholamines reduce [K+] in ECF?

A

Act via β2 adrenoreceptors

Stimulate Na-K-ATPase

23
Q

How does alkalosis cause hypokalaemia?

A

H+ excreted from cells to correct alkalosis

Get reciprocal K+ shift into cells because the inside becomes electronegative

24
Q

How does exercise increase ECF potassium conc?

A

Skeletal muscle contraction causes net release of potassium during recovery phase of action potential so K+ exits cells
Skeletal muscle damage also releases K+

25
Q

How is hyperkalaemia prevented in exercise?

A

Uptake of potassium by non-contacting tissues

Release of catecholamines

26
Q

How can cessation of exercise lead to hypokalaemia?

A

Non-respiring tissues still taking up potassium
Can drop to <3mmol
Cause sudden death

27
Q

What can cause cell lysis and release of potassium into ECF?

A

Trauma in skeletal muscle causing muscle fell necrosis
Intravascular haemolysis due to eg incompatible blood transfusion or G6PD deficiency
Chemotherapy - release of potassium from tumour cell lysis

28
Q

Why can diabetics become hyperkalaemic?

A

If they go into diabetic ketoacidosis
Increase in plasma and ECF toxicity causes water to move from ICF to ECF
Increases [K+] in cells so K+ leaves down conc gradient

Also acidosis causes increased uptake of H+ increased loss of K+ from cells.

29
Q

Can hypokalaemia cause acidosis or alkalosis?

A

Alkalosis

30
Q

How does hypokalaemia cause cardiac arrhythmias?

A

Hyperpolarises cardiac cells
More fast Na+ channels available in active form
Heart more excitable

31
Q

Causes of hypokalaemia?

A 
Alkalosis
Inadequate intake
Excessive loss 
-vomiting
-diarrhoea
-diuretics
-osmotic diuresis (diabetes)
-high aldosterone
32
Q

Clinical features of hypokalaemia?

A

Heart and neuromuscular dysfunction

  • paralytic ileus
  • muscle weakened
  • dysfunction of CD cells - unresponsive to ADH - nephrogenic diabetes
33
Q

Treatment of hypokalaemia?

A

Treat cause
K+ replacement (IV/oral)
If due to high aldosterone - K+ sparing diuretics blocking action of aldosterone on principal cells eg Amiloride
Aldosterone antagonist - spironolactone

34
Q

How does hyperkalaemia cause heart arrhythmias?

A

Depolarises cardiac cells
More fast Na+ channels inactive
Heart less excitable

35
Q

Causes of hyperkalaemia?

A 
Inadequate renal excretion
Acute/chronic kidney injury
Reduced mineralocorticoid effect
K+ sparing diuretics
ACE inhibitors
Adrenal insufficiency
Acidaemia
Cell lysis
K+ shift
36
Q

Clinical features of hyperkalaemia?

A

Heart and neuromuscular dysfunction

  • paralytic ileus
  • acidosis
37
Q

Treatment of hyperkalaemia?

A

Emergency

  • Ca2+ gluconate to reduce effect on heart
  • IV insulin and glucose
  • dialysis to remove excess K+

Long term

  • dialysis
  • oral potassium binding resins - bind in the gut
  • reduce intake
  • treat cause

Urinary (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions