An action potential in a neuronal membrane differs from a graded potential in that
A. movement of Na+ and K+ across cell membranes mediate action potentials, while graded potentials do not involve movement of Na+ and K+.
B. an action potential is propagated without decrement, whereas a graded potential decrements with distance.
C. an action potential has a threshold, whereas a graded potential is an all-or-none phenomenon.
D. action potentials vary in size with the size of a stimulus, while graded potentials do not.
E. an action potential requires the opening of Ca2+ channels, whereas a graded potential does not.
Answer: B
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