Spontaneous release of acetylcholine at the neuro?muscular junction produces:

A i.e. Miniature end plate potential Small quanta (packets) of acetylcholine (Ach) are released randomly from the nerve cell membrane at rest, each producing a minute depolarizing spike called a miniature end- plate potential.Q - Miniature end plate potential does not result in firing of muscle fibre Its about 0.5 my in amplitude. - The size of quanta of Ach released varies directly with Ca2+ concentration & inversely with Mgt' conc. At the end plate. When a nerve impulse reaches the ending, the number of quanta released increases by several order of magnitude, and the result is the large end plate potential that exceeds the firing level of muscle fiber.