Acetylcholine has two types of receptors: muscarinic and nicotinic, these receptors are functionally and structurally different. Nicotinic receptors are ionotropic, meaning that ions flow through it when acetylcholine binds to it. It acts as a channel for the ions that cross it, especially sodium, and this causes the depolarization of the cell. There are two types of nicotinic receptors formed by different subunits, N1 are found in the neuromuscular junctions allowing muscle movement, and N2 is found in the brain. Muscarinic receptors, however, use G-protein coupled, when acetylcholine binds to the receptor, the protein changes its shape so that it allows phosphorylating second messengers. There are five types of muscarinic receptors, M1, M2
