Autorhythmicity in the heart refers to the ability of cardiac muscle cells to spontaneously depolarize and generate action potentials.

Autorhythmicity in the heart refers to the ability of cardiac muscle cells to spontaneously depolarize and generate action potentials.

• A. True
• B. False
• C. Only with neural stimulation
• D. Only in atrial cells

Answer: (A)

Autorhythmicity means certain cardiac cells—the pacemaker cells of the conducting system—can spontaneously depolarize and fire action potentials, setting the heart rate. These cells, especially in the sinoatrial node, have unstable resting potentials and “funny” currents that cause diastolic depolarization, so they reach threshold and generate impulses without any neural input. The impulse then propagates through the AV node and the rest of the conduction pathway to coordinate contraction. Autonomic nerves can modulate the rate and strength of this activity, but initiation does not require neural stimulation. The working muscle cells of the heart do not normally depolarize on their own; they respond to pacemaker impulses rather than spontaneously pacing. So the statement is true.

Autorhythmicity means certain cardiac cells—the pacemaker cells of the conducting system—can spontaneously depolarize and fire action potentials, setting the heart rate. These cells, especially in the sinoatrial node, have unstable resting potentials and “funny” currents that cause diastolic depolarization, so they reach threshold and generate impulses without any neural input. The impulse then propagates through the AV node and the rest of the conduction pathway to coordinate contraction. Autonomic nerves can modulate the rate and strength of this activity, but initiation does not require neural stimulation. The working muscle cells of the heart do not normally depolarize on their own; they respond to pacemaker impulses rather than spontaneously pacing. So the statement is true.