The cardiac electrical impulse normally begins spontaneously in the sinoatrial (SA) node because of what reason?
A)It has a superior location in the right atrium.
B)It is the only area of the heart capable of spontaneous depolarization.
C)It has rich sympathetic innervation via the vagus nerve.
D)It depolarizes more rapidly than other automatic cells of the heart.

Question

Quizplus · Accepted Answer

The electrical impulse normally begins in the SA node because its cells depolarize more rapidly than other automatic cells at a rate of 60 to 100 beats/min. The SA node's location does not influence this activity. Other areas of the heart include the AV node and the Purkinje fibers. The vagus nerve causes the heart rate to slow as part of the parasympathetic nervous system.

The Cardiac Electrical Impulse Normally Begins Spontaneously in the Sinoatrial