Select the correct statement about the function of myocardial cells.
A) The influx of potassium ions from extracellular sources is the initiating event in cardiac muscle contraction.
B) The refractory period in skeletal muscle is much longer than that in cardiac muscle.
C) The entire heart contracts as a unit or it does not contract at all.
D) Cardiac muscle cells are innervated by sympathetic, parasympathetic, and somatic nerve fibers so that the nervous system can increase heart rate.

Question

Quizplus · Accepted Answer

The entire heart must contract as a unit in order to efficiently pump blood. This is due to intercalated discs and gap junctions that allow for the spread of electrical impulses throughout the myocardial cells. The other statements are false; the influx of calcium ions is the initiating event in cardiac muscle contraction, the refractory period is actually longer in cardiac muscle, and cardiac muscle cells are not innervated by somatic nerve fibers.

Select the Correct Statement About the Function of Myocardial Cells