What neurotransmitter is primarily released when the parasympathetic nervous system is activated?

The primary neurotransmitter released when the parasympathetic nervous system is activated is acetylcholine. This neurotransmitter is responsible for transmitting signals in the body that promote a state of rest and digest, counteracting the effects of the sympathetic nervous system, which prepares the body for a "fight or flight" response.

When the parasympathetic nervous system is engaged, acetylcholine is released at the neuromuscular junctions and synapses of relevant organs. This release leads to effects such as decreased heart rate, increased gastrointestinal activity, and other functions that support relaxation and restorative processes in the body.

The role of acetylcholine in the parasympathetic nervous system underscores its importance in maintaining homeostasis and supporting bodily functions during calm states, contrasting with the actions of other neurotransmitters like norepinephrine, which is predominantly involved in the sympathetic nervous system's responses.