Cardiac M Uscle Cannot Increase Its Strength of Contraction by Repetitive

question 11

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