Acetylcholine

Acetylcholine (ACh), the first neurotransmitter ever to be identified, is a small- molecule excitatory neurotransmitter with a wide variety of known functions. In the sympathetic and parasympathetic nervous systems and at all neuromuscular junctions, ACh is used to signal muscle movement. Within the central nervous system, cholinergic cells (neurons that use ACh as a neurotransmitter) are found in several different locations of the brain, including the striatal complex, the basal forebrain, the diencephalon, pontomesencephalic cell groups, and the medulla. Depending on which area of the brain it is found in, ACh may be involved in any one of several different functions. Some of these functions include the conduction of pain, the regulation of neuroendocrine function, the regulation of REM sleep cycles, and the process of learning and memory formation.

Images to click and see:

The ACh molecule

The Ach and Synapse