Acetylcholine (ACh)
Acetylcholine (ACh) is one of the most common neurotransmitters of the vertebrate nervous system, ACh is a chemical (CH3COOCH2CH2N+(CH3)3) that transmits impulses between the ends of two adjacent nerves or neuromuscular junctions. Released by nerve stimulation (exciting or inhibiting), it is confined largely to the parasympathetic nervous system, where it diffuses across the gap of the synapse and stimulates the adjacent nerve or muscle fiber. It rapidly becomes inactive by the enzyme cholinesterase, allowing further impulses to occur.