Question

Parasympathetic nervous system stimulation of the heart has little effect on force of contraction because the vagus nerve does not supply most of the ventricular myocytes. True/False

Answer 1

False. Parasympathetic stimulation releases acetylcholine and inhibits contraction, leading to a decrease in the force of ventricular contraction. However, parasympathetic fibers are more widespread in the atria than in the ventricles.

Step-by-step explanation:

False

The statement is false. The parasympathetic nervous system does supply the ventricular myocytes, but its stimulation has little effect on the force of contraction of the heart. Parasympathetic stimulation releases the neurotransmitter acetylcholine (ACh) at the neuromuscular junction from the vagus nerve. ACh slows heart rate, hyperpolarizes the cardiac muscle cells, and inhibits contraction, thereby decreasing the strength of contraction and stroke volume. However, it is important to note that parasympathetic fibers are more widespread in the atria than in the ventricles, so the primary site of action is in the upper chambers.