A muscle cell cannot be depolarized again during which phases of an action potential?
a. End of 0 to the be-ginning of 2 c. End of 1 to the be-ginning of 4
b. Beginning of 1 to the end of 3 d. Beginning of 0 to the middle of 3
ANS: D
The period from the beginning of phase 0 to the middle of phase 3 is referred to as the absolute refractory period or effective refractory period, because regardless of the strength of the stimulus, the myocyte cannot be depolarized again.
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