potassium and hydrogen Flashcards
Potassium is a largely …… cation?
Intracellular.
The major extracellular cation is?
Sodium.
How much potassium is stored in cells?
95%. So 5% ECF but kept within tight limits to prevent cardiac problems.
Intracellular potassium is needed for?
Cell growth (needed for enzyme function)
Hyperkalaemia initially makes cells?
More excitable but also slows repolarisation of the cell if resting potential is greater than threshold potential.
What are the sources of potassium?
Passive diffusion in SI.
Active transport it response to aldosterone in colon.
sometimes,
Haemolysis and muscle damage
The kidneys remove what percentage of potassium? What percentage is removed by GIT?
90-95% is removed via kidneys.
5-10% by the GIT.
The translocation from ECF to ICF
prevents?
life threatening hyperkalaemia until the kidneys can excrete the rest.
Uptake of potassium into liver & muscle cells is
promoted by hormones?
Insulin & adrenaline (affects beta 2 ßç)
— Thereby increasing activity Na/K ATPase
What situations promote the release of potassium from ICF?
Insulin deficiency, aldosterone deficiency, acidaemia, exercise and increased ECF osmolality.
What happens K+ at the glomerulus?
It is freely filtered.
How much K+ is reabsorped in PCT?
70%
How much K+ is reabsorped in the ascending limb?
10-20%
What happens to K+ in the distal nephron and collecting ducts?
Net reabsorption or secretion in
distal nephron. First part of collecting duct
DETERMINES RENAL EXCRETION
DEPENDING ON NEED
What does high Na+ do to K+?
Leads to increased secretion of it.
What are the effects of aldosterone deficiency?
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.
Aldosterone promotes?
Distal tubule Na+ reabsorption and K+ excretion into tubular lumen.
ENaC stands for?
Epithelial sodium channel- amiloride sensitive
What happens to K+ excretion in acidosis?
Decreases we need a more alkaline environment and loosing it would cause further acidosis.
Aldosterone is secreted by?
zona glomerulosa of adrenal gland in response to high K+
What stimulates and inhibits aldosterone release?
corticotrophin (ACTH) } stimulatory
angiotensin II (ANG II)
inhibitory
- Atrial Natriuretic Peptide (AN P)
What does insulin do to K+?
Insulin is agonist for Na/k ATPase pump therefore K+ moves into cells.
What species is prone to hyperkalaemic periodic paralysis (HYPP)?
The horse
What type of cat is prone to hypokalaemic periodic paralysis?
Burmese cats.
