What occurs when the parasympathetic nervous system is stimulated?

When the parasympathetic nervous system is stimulated, acetylcholine is released, which plays a key role in regulating heart rate. This neurotransmitter acts on the heart's pacemaker cells in the sinoatrial node, leading to a decrease in heart rate. The primary function of the parasympathetic nervous system is to promote a "rest and digest" state, which contrasts with the "fight or flight" response of the sympathetic nervous system.

During this process, the intrinsic heart rate is decreased, allowing for a more relaxed state in the body. This is crucial during times of rest and recovery, helping to conservatively manage the body's resources. Therefore, the release of acetylcholine is central to the parasympathetic response, resulting in a decrease in the heart rate and promoting overall relaxation within the system.