Cardiac M Uscle Cannot Increase Its Strength of Contraction by Repetitive

Multiple Choice

Cardiac m uscle cannot increase its strength of contraction by repetitive stimulation (wave summation) because

A) The action potential lasts hundreds of milliseconds, as long as the cardiac cycle
B) The SR empties its Ca²⁺ with every heart beat
C) The SA node fires too frequently for the cardiomyocytes to follow
D) The absolute refractory period is longer than the action potential
E) The bundle of His has no reserve capacity