Karteikarten
Potassium Balance
Karten in diesem Stapel (34)
- 1In which foods can potassium be found?Leafy vegetables, most fruit and fruit juice, potatoes
- 2Where is concentration of potassium highest, intra or extra cellularly?Intracellularly
- 3What is meant by acute regulation of K+?The distribution of K+ between intracellular and extracellular compartments.
- 4What is meant by chronic regulation of K+?The kidneys adjusting excretion and reabsorption of K+.
- 5What are the 3 functions of K+?1. Determines the osmolality of intracellular fluid and therefore also the fluid volume
2. Determines RMP
3. Affects vascular resistance - 6How is the intracellular K+ mostly maintained?By Na+/K+ ATPase pumps in the membranes of cells.
- 7Name 3 hormones that help regulate K+.1. Insulin
2. Aldosterone
3. Adrenaline - 8Which equation is used to calculate the membrane potential based on intra and extra cellular concentrations of an ion?The Nernst Equation
- 9What is the boundary for hyperkalaemia?plasma concentration K+ > 5.5mM
- 10What is the boundary for hypokalaemia?Plasma concentration K+ < 3.5mM
- 11What is particularly affected by changes in plasma K+ concentration?Firing of action potentials
- 12How is this changed in hyperkalaemia?There is easier depolarisation as RMP is less negative, so it is easier to reach threshold.
- 13How is it changed in hypokalaemia?Membranes are harder to depolarise, as RMP is more negative and therefore further away from threshold (hyperpolarised).
- 14Where can this be particularly dangerous?In cardiac tissue, as the depolarisation/repolarisation pattern in the membrane potentials is what gives the normal cardiac rhythm on an ECG.
- 15What can cause hypokalaemia? (4)1. Long-term use of diuretics without KCl compensation
2. Hyperaldosteronism
3. Prolonged vomiting causing Na+ loss and therefore aldosterone causing K+ excretion
4. Profuse diarrhoea - 16What is the hormonal effect of hypokalaemia?Decreased release of insulin, aldosterone and adrenaline
- 17What causes hyperkalaemia? (3)1. Insufficient renal excretion
2. Increased release from damaged cells (chemotherapy, prolonged exercise, severe burns etc.)
3. Addison's disease - 18When does hyperkalaemia become particularly dangerous?Plasma K+ concentration > 7mM causes asystolic cardiac arrest
- 19What can be given to stimulate K+ influx back into cells in this case?Insulin to stimulate Na+/K+ ATP ase pumps
- 20What should also be given and why?Glucose to prevent hypoglycaemia
- 21In treatments for CVD, what are the associated risks?1. Risk of hyperkalaemia when drugs such as beta blockers and ACE inhibitors are used (decrease activity of Na+/K+ ATPase pumps, prevent secretion of aldosterone)
2. Risk of hypokalaemia when loop diuretics used (increases K+ excretion) - 22In the kidneys, ___ and ____ are filtered freely, then ___________. The ________ of this in the __ __ __ is always more or less constant.Na+ and K+,
reabsorbed,
fraction,
PCT - 23What mechanisms allow K+ transport in the PCT? (3)1. Na+/K+ ATPase pumps in the basolateral membrane,
2. K+ channels in the basolateral membrane,
3. Passive flow paracellularly between tight junctions. - 24What mechanisms allow transport of K+ in the thick ascending limb of the Loop of Henle? (3)1. Na+/K+ ATPase pumps on the basolateral surface
2. K+ channels on the basolateral surface
3. Na+/K+ symporter on the apical surface - 25What mechanisms allow transport of K+ in the DCT? (3)1. Na+/K+ ATPase pumps on the basolateral surface
2. K+ channels on both the basolateral and the apical surfaces
3. Possibly a Cl-/K+ symporter on the apical surface - 26How is secretion of K+ back into the tubule encouraged in the DCT?ENaCs (epithelial Na+ channels) cause influx of Na+ so encourage efflux of K+ through K+ channels on the apical surface.
- 27What are the effects of aldosterone on K+ secretion?1. Increases activity of Na+/K+ ATPase pumps (intracellular concentration of K+ rises so increases concentration gradient)
2. Increases number of ENaCs so increases electrochemical gradient
3. Increases permeability of the apical membrane to K+ - 28What stimulates secretion of aldosterone?Increased plasma concentration of K+
- 29What else can enhance K+ secretion?Faster flow rate in the tubular lumen, as this removes the K+ more quickly and maintains a high concentration gradient.
- 30What is thought to be the mechanism in place in severe hypokalaemia?Reabsorption of K+ by the alpha-intercalated cells of the collecting ducts by a K+/H+ ATP antiporter.
- 31What effect does the plasma pH have on K+?In alkalosis, Na+/K+ATPase pumps work faster so can lead to hypokalaemia.
In acidosis, these pumps slow down so K+ shifts to extracellular compartment and leads to hyperkalaemia. - 32How does Addison's disease cause imbalance of Na+/K+?Deficiency of aldosterone, so K+ shifts out of cells (resulting in hyperkalaemia)
- 33What is Conn's syndrome?Hyperaldosteronism due to adenoma in adrenal cortex secreting aldosterone uncontrollably.
- 34How does this disrupt K+ balance?Too much aldosterone causes increased Na+ reabsorption and K+ excretion, resulting in hypokalaemia and hypernatraemia (leading to hypertension).
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- Degree KBF1 Karteikarten am Potassium Balance, erstellt von Hannah Tribe am 27/05/2014.
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- Hannah Tribe
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