What distinguishes the contraction stimulus of cardiac contractile cells from that of skeletal muscle fibers?

Skeletal muscle fibers are activated by somatic motor neurons, while cardiac cells generate action potentials via pacemaker activity.

Cardiac contractile cells require anaerobic metabolism, whereas skeletal fibers depend solely on aerobic metabolism.

Cardiac cells require direct stimulation from motor neurons, while skeletal fibers generate their own action potentials.

Skeletal muscle fibers have a long refractory period, unlike cardiac cells.