Block 4.2 -- Potassium, Calcium, and Phosphate Flashcards
(49 cards)
What regulates K+ in plasma?
Kidney
Regulation of K+ adds an extra variable, as most K+ is where? This means cellular shifts must be considered.
Intracellular (Extracellular to intracellular or intracellular to extracellular)
What promotes intracellular accumulation of K+ (fed state)?
Insulin
What stimulates cellular uptake via Na+/K+ ATPase (increased extracellular flux from action potentials in muscle cells)?
Epinephrine
What (increased H+) stimulates potassium efflux?
Acidemia
Small changes in [K+] plasma can have profound effects on cellular function, especially the heart. This makes what of [K+] plasma critical?
Control of
Is hyperpolarization when the inside or outside is more negative?
Inside more negative
Is depolarization when the inside or outside is more negative?
Outside more negative
Is hypokalemia or hyperkalemia when there is less [K+] in the ECF?
Hypokalemia
Usually more 90% of filtered K+ is reabsorbed. Where does 70% occur and where does 20% occur?
70% in the proximal tubule and 20% in the ascending limb of the Loop of Henle
The amount of K+ secreted is controlled by the amount what?
Excreted
The primary mechanism of K+ reabsorption in the proximal tubule is passive movement of K+ via what route due to slightly electropositive lumen?
Paracellular
‘Leaky’ tight junctions and increasing flux of Na+ and water may ‘what’ K+ along?
Carry
Reabsorption of potassium is relatively fixed, being what type of reabsorption?
Obligate
What cells in the collecting duct reabsorb K+? What is in, in part, controlled by?
Principal cells and aldosterone
Reabsorption of Na+ from the lumen via ENaC to the interstitium creates a negative lumen electrical gradient which favors what secretion into lumen?
K+ secretion
Increase in [K+] plasma directly stimulates release of aldosterone from adrenal, which stimulates Na+ reabsorption and K+ what?
Secretion
Where is calcium stored and where most of it in the body is?
In the bone
Calcium is relatively low in extracellular and intracellular fluid, which is sequestered in organelles – what?
Sarcoplasmic reticulum
Calcium has what excitability, muscle what, and what of bones and teeth?
1). Neuronal excitability
2). Muscle contraction
3). Mineralization of bones and teeth
What regulate plasma Ca2+ and free calcium?
Kidneys
The small proportion of total body calcium in the what is regulated within the narrow range?
Extracellular fluid
Calcium entry via gut what and release from what?
1). Gut absorption
2). Release from bone
Calcium loss via entering what and urinary what?
1). Entering bone
2). Urinary excretion
