potassium and hydrogen

Question 1

Potassium is a largely …… cation?

Answer 1

Intracellular.

Question 2

The major extracellular cation is?

Answer 2

Sodium.

Question 3

How much potassium is stored in cells?

Answer 3

95%. So 5% ECF but kept within tight limits to prevent cardiac problems.

Question 4

Intracellular potassium is needed for?

Answer 4

Cell growth (needed for enzyme function)

Question 5

Hyperkalaemia initially makes cells?

Answer 5

More excitable but also slows repolarisation of the cell if resting potential is greater than threshold potential.

Question 6

What are the sources of potassium?

Answer 6

Passive diffusion in SI.
Active transport it response to aldosterone in colon.
sometimes,
Haemolysis and muscle damage

Question 7

The kidneys remove what percentage of potassium? What percentage is removed by GIT?

Answer 7

90-95% is removed via kidneys.

5-10% by the GIT.

Question 8

The translocation from ECF to ICF

prevents?

Answer 8

life threatening hyperkalaemia until the kidneys can excrete the rest.

Question 9

Uptake of potassium into liver & muscle cells is

promoted by hormones?

Answer 9

Insulin & adrenaline (affects beta 2 ßç)

— Thereby increasing activity Na/K ATPase

Question 10

What situations promote the release of potassium from ICF?

Answer 10

Insulin deficiency, aldosterone deficiency, acidaemia, exercise and increased ECF osmolality.

Question 11

What happens K+ at the glomerulus?

Answer 11

It is freely filtered.

Question 12

How much K+ is reabsorped in PCT?

Answer 12

70%

Question 13

How much K+ is reabsorped in the ascending limb?

Answer 13

10-20%

Question 14

What happens to K+ in the distal nephron and collecting ducts?

Answer 14

Net reabsorption or secretion in
distal nephron. First part of collecting duct
DETERMINES RENAL EXCRETION
DEPENDING ON NEED

Question 15

What does high Na+ do to K+?

Answer 15

Leads to increased secretion of it.

Question 16

What are the effects of aldosterone deficiency?

Answer 16

Causes dimished Na+ reabsorption in the distal tubule therefore K+ from the blood is not pumped into tubular cells in exchange for Na+ so levels of K+ can rise dangerously high in the blood called hyperkalaemia. This is happens in a disease called Addisons/aldosterone deficiency.

Question 17

Aldosterone promotes?

Answer 17

Distal tubule Na+ reabsorption and K+ excretion into tubular lumen.

Question 18

ENaC stands for?

Answer 18

Epithelial sodium channel- amiloride sensitive

Question 19

What happens to K+ excretion in acidosis?

Answer 19

Decreases we need a more alkaline environment and loosing it would cause further acidosis.

Question 20

Aldosterone is secreted by?

Answer 20

zona glomerulosa of adrenal gland in response to high K+

Question 21

What stimulates and inhibits aldosterone release?

Answer 21

corticotrophin (ACTH) } stimulatory
angiotensin II (ANG II)
inhibitory
- Atrial Natriuretic Peptide (AN P)

Question 22

What does insulin do to K+?

Answer 22

Insulin is agonist for Na/k ATPase pump therefore K+ moves into cells.

Question 23

What species is prone to hyperkalaemic periodic paralysis (HYPP)?

Answer 23

The horse

Question 24

What type of cat is prone to hypokalaemic periodic paralysis?

Answer 24

Burmese cats.