Final answer:
Cardiomyocytes have a longer polarization period due to a sustained plateau phase caused by calcium influx from outside the cell, leading to a longer contraction necessary for effective blood pumping.
Step-by-step explanation:
Cardiomyocytes have a much longer polarization period than skeletal muscles due to their distinct electrical pattern which includes a rapid depolarization followed by a plateau phase and then repolarization. This extended period of depolarization is possible because of the sustained influx of Ca2+ through voltage-gated calcium channels in the sarcolemma of cardiac muscle fibers. Unlike skeletal muscles, where calcium comes mainly from the sarcoplasmic reticulum (SR), cardiac muscles require a significant amount of Ca2+ from outside the cell. The prolonged plateau phase and the subsequent slow onset of contraction are essential for the cardiac muscle cells to pump blood efficiently before they can fire again, resulting in a much longer contraction.