The cardiac electrical impulse normally begins spontaneously in the SA node because:
A) of its 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 SA node is capable of spontaneous depolarization because it has a unique ability to depolarize more rapidly than other automatic cells in the heart. This is due to its unique structure and ion channel distribution, which allows for the fastest depolarization rate.

The Cardiac Electrical Impulse Normally Begins Spontaneously in the SA