Which physiological effect would you expect from an increase in parasympathetic nervous system activity on the heart?

A. Arteries have thicker walls than veins: Arteries have thick, muscular, and elastic walls to withstand high pressure from the heart’s pumping action. This structural feature allows them to maintain blood flow and pressure throughout the circulatory system.

B. Arteries have valves inside them: Arteries generally do not have valves because blood flows under high pressure from the heart. Valves are primarily found in veins to prevent backflow.

C. Veins have thicker walls than arteries: Veins have thinner walls than arteries since they carry blood under lower pressure. Their thinner walls allow veins to expand and accommodate larger volumes of blood.

D. Veins have more elastic tissue than arteries: Arteries contain more elastic tissue to handle pulsatile blood flow. Veins have less elastic tissue and rely on valves and surrounding muscles to help return blood to the heart.

A. Increased heart rate: Increased heart rate is a result of sympathetic nervous system stimulation, not parasympathetic activity.

B. Increased cardiac contractility: The parasympathetic system has minimal effect on contractility; it primarily influences heart rate rather than the force of contraction.

C. Decreased heart rate: Parasympathetic stimulation, mainly via the vagus nerve, releases acetylcholine, which slows the sinoatrial node firing rate and decreases heart rate.

D. Increased conduction velocity: Parasympathetic activity slows conduction through the atrioventricular node, reducing conduction velocity rather than increasing it.