Final answer:
The motor end plate is a specialized region of the muscle fiber sarcolemma with ACh receptors, essential for muscle contraction. Binding of ACh to these receptors at the motor end plate causes depolarization by allowing Na+ ions to enter the cell, which leads to the generation of an action potential and subsequent muscle contraction.
Step-by-step explanation:
What is the Motor End Plate?
The motor end plate is the part of the muscle fiber's sarcolemma at the neuromuscular junction, equipped with receptors for the neurotransmitter acetylcholine (ACh). It contains junctional folds which increase the surface area available for ACh receptors. These receptors are specialized protein channels that respond to the binding of ACh.
Receptor Function and Action Potential Creation
When an action potential reaches the axon terminal of a motor neuron, it triggers the release of ACh into the synaptic cleft. The released ACh then diffuses across to the motor end plate and binds to the ACh receptors. This binding of ACh causes the receptor channels to open, allowing Na+ ions to enter the muscle cell, leading to a reduction in the voltage difference across the cell membrane known as depolarization. This initial depolarization, referred to as an end-plate potential, stimulates adjacent sodium channels to open, propagating the action potential along the sarcolemma and resulting in muscle contraction.