Excitation is the process, in which action potentials in the nerve fiber lead to action potentials in the muscle fiber.The process begins with a nerve signal stimulating a voltage-gated calcium ion channel to open, allowing the ions to enter the synaptic knob.The ions stimulate the release of acetylcholine into the synaptic cleft.There is then a rapid fluctuation in membrane voltage at the motor end plate, called the end-plate potential.Areas of the sarcolemma near the motor plate have gates that open, moving ions, which causes the action potential that excites the muscle fiber.