The neurotransmitter acetylcholine, abbreviated ACh, is a neurotransmitter that is used widely in both the central and peripheral nervous systems. In the peripheral nervous system, it will bind to ACh receptors on skeletal muscle fibers. This will release large amounts of sodium into the muscle, which then leads to muscle contraction. In this way acetylcholine acts as the primary messenger from the brain to the muscles to give them orders to execute functions. It also plays a role in cardiac muscle, where it is released to have an opposite, calming effect to slow heart rate.
In the central nervous system ACh is believed to have strong effects upon learning and brain processing speed. An area where it is largely produced is the basal forebrain, which is why damage to this area is often a precursor to Alzheimer’s. Slight imbalances of ACh can have large effects other than Alzheimer’s. Too little ACh will often lead to paranoia, and too little will lead to an obsessive want for fatty foods. The latter is caused because fatty foods are rich in choline, a chemical precursor of ACh. [Snyder S.H.]