What effect does acetylcholine have in the parasympathetic nervous system?

Acetylcholine plays a crucial role in the functioning of the parasympathetic nervous system, which is often referred to as the "rest and digest" system. When acetylcholine is released in this context, it activates various receptors that lead to a reduction in heart rate, an increase in digestive processes, and an overall state of relaxation in the body. This promotes functions such as salivation, increased gastric motility, and secretion of digestive enzymes, all of which are aligned with the body’s restorative processes.

This response contrasts sharply with the actions of the sympathetic nervous system, which prepares the body for "fight or flight" responses through elevated heart rates and redirecting energy away from digestion. Therefore, the activation of acetylcholine in the parasympathetic nervous system indeed promotes relaxation and supports digestive functions, making this the correct choice regarding its effect.