Acetylcholine is a neurotransmitter, a chemical messenger that plays a crucial role in transmitting signals in the nervous system. It is primarily involved in muscle contraction, enabling movement by relaying messages from nerve cells to muscles. Additionally, acetylcholine is important for various functions in the brain, including memory and learning. This neurotransmitter is synthesized in nerve terminals and released into the synaptic cleft, where it binds to receptors on target cells. After its action, acetylcholine is broken down by the enzyme acetylcholinesterase, ensuring that signals are short-lived and allowing for precise control of muscle and nerve activity.