The electric activity of the motor end-plate

Abstract

At the nerve-muscle junction, a specific process occurs which is not found during the propagation of impulses along nerve or muscle fibres; the nerve impulse causes acetylcholine (Ach) to be released from the motor nerve endings, and this substance depolarizes the end-plate surface of the muscle fibre by a specific chemical reaction. The transient local depolarization of the muscle fibre which is so produced has been called the end-plate potential (e.p.p.). The e.p.p., then, unlike the nerve or muscle impulse, is not itself produced by electric stimulation (direct spread of electric current from nerve to muscle has, in fact, never been demonstrated and appears to be indetectably small). On the other hand, the e.p.p. electrically stimulates the surrounding region of the muscle fibre, and so gives rise to the propagation of a new impulse.