Acetylcholine is a neurotransmitter that is essential for many functions in both the central and peripheral nervous systems. In the peripheral nervous system, acetylcholine activates muscles and is a major part of the autonomic nervous system, influencing activities such as muscle contraction, heart rate, digestion, and dilation of blood vessels. In the central nervous system, it plays a role in arousal, attention, memory, and motivation. Acetylcholine is also involved in the promotion of rapid eye movement (REM) sleep. Disruptions in acetylcholine production can contribute to neurological conditions, such as Alzheimer’s disease, where there is a noted decrease in acetylcholine concentrations in certain parts of the brain.