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

Question

Quizplus · Accepted Answer

Cardiac muscle cells are connected by gap junctions which allow for rapid, synchronized depolarization and contraction of the entire heart as a unit. This is known as a functional syncytium. Cardiac muscle cells are also innervated by sympathetic and parasympathetic nerves, but not somatic nerves. The refractory period in cardiac muscle is actually longer than that in skeletal muscle, which helps prevent tetanic contractions. The influx of calcium ions from extracellular sources, not potassium ions, is the initiating event in cardiac muscle contraction.

Select the Correct Statement About the Function of Myocardial Cells