Final answer:
The acetylcholine receptor in skeletal muscle cells is a ligand-gated ion channel, which when activated by acetylcholine, initiates an action potential leading to muscle contraction.
Step-by-step explanation:
The acetylcholine receptor in skeletal muscle cells is a ligand-gated ion channel. When an action potential arrives at the motor neuron's axon terminal, it causes the release of acetylcholine (ACh), which then diffuses across the synaptic cleft to the motor end-plate on the muscle fiber's sarcolemma. There, ACh binds to ACh receptors, which are ligand-gated ion channels, leading to their opening. The influx of Na+ ions through these channels depolarizes the sarcolemma, initiating an action potential that spreads across the entire cell, ultimately triggering muscle contraction.