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Flashcards in Urinary 4 - Control of K+ Deck (27):
1

Where is the majority of K+ found in the body?

Intracellular fluid of:
- Skeletal muscle cells
- Liver cells
- RBCs
- Bone cells

2

What is the approximate intracellular fluid [K+]?

120-150 mM

3

What is the approximate extracellular fluid [K+]?

3.5-5 mM

4

Is the concentration of K+ higher in intracellular fluid or extracellular fluid?

Higher [K+] INTRAcellularly

5

How the the difference of [K+] between the ICF and ECF maintained?

Na+/K+-ATPase

6

What is the average intake of K+ during a meal?

30 mM

7

What is the average time taken for excretion of K+ after a meal?

6-12hrs

8

What are the main treatments used for hyperkalaemia?

- IV Insulin and Dextrose
- IV Calcium Gluconate
- Salbutamol

9

Why is Insulin and Dextrose given to treat hyperkalaemia?

Insulin stimulates Na+/K+-ATPase (increasing absorption of K+ into cells)
Dextrose prevents hypoglycaemia occurring

10

Hyperkalaemia stimulates the secretion of which 2 hormones? Why?

1) Insulin
2) Aldosterone
(Also catecholamines)
These increase Na+/K+-ATPase activity, driving K+ absorption into cells to decrease the ECF [K+]

11

What percentage of K+ is reabsorbed in the PCT?

67%

12

In what part of the tubule does the majority of K+ reabsorption occur?

PCT

13

What percentage of K+ is reabsorbed in the TAL (Thick ascending limb of LoH)?

20%

14

via what channel is K+ reabsorbed across the apical membrane of the TAL cells (Thick ascending limb of LoH)?

Na+/K+/2Cl- symporter (NKCC2)

15

In what part of the tubule is K+ passively reabsorbed?

PCT

16

In what part of the tubule is K+ actively reabsorbed?

- TAL (thick ascending limb of LoH)
- Distal tubule
- Collecting duct

17

What type of cell actively reabsorbs K+ from the lumen of the late distal tubule and early collecting duct? What channel mediates this active reabsorbtion?

Alpha Intercalated cells
H+/K+-ATPase

18

What cells of the tubule secrete K+? What channels are involved?

Principle cells (of late DT and early CD)
Na+/K+-ATPase on the basolateral membrane
ROMK on the apical membrane

19

How would acidosis affect K+ secretion into the tubular lumen?

Inhibits Na+/K+-ATPase = inhibits K+ secretion

20

How would an increase in Aldosterone affect K+ secretion into the tubular lumen?

Increase K+ secretion

21

Name the main causes of HYPERkalaemia:

- Increased intake
- Cell lysis (tumour/trauma)
- Exercise
- Decreased renal excretion (AKI/CKI/drugs)
- Diabetic ketoacidosis
- Metabolic acidosis

22

How does DKA and metabolic acidosis lead to hyperkalaemia?

Acidosis inhibits the Na+/K+-ATPase, inhibiting K+ renal secretion

23

How does exercise cause an increase in serum K+? How does the body reverse this quickly?

- K+ released from muscle cells during exercise as Na+/K+-ATPase cannot keep up with the repeated repolarisation
- Exercise causes increase in catecholamines, which increase activity of Na+/K+-ATPase, driving the uptake of K+ back into the cells

24

What are the common symptoms of hyperkalaemia?

- Heart abnormalities (arrhythmias, bradycardia)
- Fatigue and muscle weakness

25

In an emergency situation, how would you remove excess K+ from a hyperkalaemic patient?

Dialysis

26

Name some of the common causes of HYPOkalaemia:

- Excessive loss (diarrhoea, vomiting, diuretic drugs)
- Reduced intake (malnourished/eating disorders)
- Metabolic alkalosis

27

What are the common symptoms of hypokalaemia?

- Irregular heatbeat / palpitations
- Constipation
- Muscle weakness/tingling