Final answer:
The end plate potential is an electrical change in muscle fibers initiated by the binding of acetylcholine to receptors on the motor end plate, leading to sodium ions entering the cell and causing depolarization.
Step-by-step explanation:
The electrical changes in the muscle fiber in response to acetylcholine (ACh) on the motor end plate is called the end plate potential. This process occurs when an action potential reaches the axon terminal of a motor neuron at a neuromuscular junction (NMJ), prompting the release of ACh into the synaptic cleft.
Once ACh binds to ACh receptors on the motor end-plate, sodium (Na+) channels open, allowing Na+ ions to enter the muscle fiber, leading to a change in voltage known as depolarization. This depolarization, the end plate potential, is critical for initiating an action potential across the muscle fiber's membrane which ultimately triggers muscle contraction, a process called excitation-contraction coupling.