Which of the following normally has a slowly depolarizing “prepotential”: (A) Sinoatrial node, (B) Atrial muscle cells, (C) Bundle of His, (D) Purkinje fibers
Answer is A. Rhythmically discharging cells have a membrane potential that, after each impulse, declines to the firing level. Thus, this prepotential or pacemaker potential triggers the next impulse.