ABSTRACT
Acetylcholine (ACh) is a major neurotransmitter (NT) of the body, utilized at cholinergic synapses in both the peripheral nervous system (PNS) and central nervous system (CNS). ACh is active at neuromuscular junctions and thereby controls muscle contractions throughout the body, both sympathetic (under conscious control) and parasympathetic (e.g., breathing and heart function), and also controls glandular secretion. Binding of ACh to postsynaptic receptors produces muscle contraction by causing a localized depolarization, which activates voltage-gated calcium channels, both at the cellular surface and intracellularly at the sarcoplasmic reticulum. Overactivation of the system can result in inappropriate muscle contraction or spasm, and blockage can produce paralysis. In the extreme, either scenario can be fatal.
