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MCAT Question A Day - 9/8/14 - Answer!

During an action potential, a cardiac muscle cell remaindepolarized much longer than a neuron. This is most likely to:

A.  prevent the initiation of another action potential during contraction of the heart.
B.  ensure that adjacent cardiac muscle cells will contract at different times.
C.  keep the neuron from firing twice in rapid succession.
D.  allow sodium voltage-gated channels to remain open long enough for all sodium to exit the cell.

A is correct. The heart requires long steady contractions in order to pump blood. We know we want adjacent heart cells to contract at the same time; B is out. We're not concerned about a neuron here; C is out. Sodium flows into the cell, not out. D is out as well.

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