For most cells, the membrane potential is closer to the Ek+ (-90 mV) than for ENa+ (+ 60 mV). This is because
a. EK+ <<<< ENa+, and systems tend toward lower energy states.
b. cells like potassium better than sodium, so they work to maintain potassium closer to its equilibrium distribution.
c. cell membranes are equally permeable to Na+ and Cl-, so every time a Na+ comes in, its depolarizing effect is negated by a Cl- ion.
d. cell membranes are more permeable to K+ than Na+, so there are a greater number of pathways available for K+ to move towards its equilibrium distribution than are available for Na+ to do the same.
e. none of these.
D
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A) brush border enzymes B) an alkaline mucus C) pepsin D) secretin E) cholecystokinin
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a) thin b) thin and thick c) thick
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A. anastomosis B. collateral circuit C. portal system D. pulmonary circuit