Potassium Homeostasis Extrarenal Flashcards
In what body compartment can you measure K concentration?
ECF
when you have a potassium disturbance what three characteristics of the body system does Dr. Moe want us to know about?
steady state - is it in 0 flux?
balance - has there been a net +ve or -ve change since the start?
deficiency - relative to physio. norms is it up or down?
how does our diet now compare to our primordial diet?
more Na, less K
what are the body’s three mechanisms to handle a K load?
cellular uptake
renal excretion
colonic excretion
what are the physio norms for potassium? (ECF, ICF)
3.5-5 ECF
100-150 ICF
how much K can a body secrete in 4-6 hours (undefined load)
50%; 40% goes to ICF, 10% goes to ECF; meaning that if you ingest 14 mEq, you’ll only spike 1.4 mEq, which is acceptable
what’s the Nernst equation?
V (mV) = 61.5 * log(Cout/Cin)
what the difference between a total body hypokalemia (or hyperkalemia) and a cell shift only potassium disturbance?
in a total body disturbance, both the numerator and denominator of the Nernst equation (Cout/Cin) would be affected, meaning that the cell’s potential would not be so dramatically altered;
OTOH, in cell shift only disturbances, only the Cout would change, resulting in a dramatic change in the resting potential of the cell
are the kidneys required for K homeostasis?
they help, but no, in rats with nephrectomies infusions of KCl were handled (and better in rats that were conditioned to a high KCl diet)
how does aldosterone affect K homeostasis?
through the GI tract
K shift into cells is controlled by which three factors?
insulin, catecholamines and pH
what’s the threshold in delta-K for the release of insulin?
1 mEq in plasma
does exogenous insulin rescue hyperkalemic status?
yes
will a pancreatectomized animal survive a potassium spike?
no, cardiac arrest will ensue
does insulin have a constant state role in regulating K levels?
yes, it reduces potassium
