Question

Cardiac Muscle SA node is spontaneously active and triggers an endogenous heart rate of about 100 beats per minute. How is it normally reduced or increased?

Answer 1

The heart rate is normally reduced or increased through the influence of the autonomic nervous system. The parasympathetic nervous system acts to decrease the heart rate, while the sympathetic nervous system acts to increase the heart rate. Parasympathetic input normally predominates.

Step-by-step explanation:

The heart rate is normally reduced or increased through the influence of the autonomic nervous system. The autonomic nervous system has two divisions: the sympathetic nervous system and the parasympathetic nervous system. The parasympathetic nervous system acts to decrease the heart rate, while the sympathetic nervous system acts to increase the heart rate. Parasympathetic input normally predominates, slowing the heart rate to a normal resting rate of about 72 beats per minute. Without parasympathetic stimulation, the pacemaker cells of the heart would generate a resting heart rate of about 100 beats per minute.