Answer:
Binding of ACh (acetylcholine) to receptors (ligand-gated) on the sarcolemma at the neuromuscular junction is vital for depolarization of the muscle fiber.
Explanation:
It allows acetylcholine to be released into this synapse when an action potential hits a neuromuscular junction. Acetylcholine attaches to the nicotinic receptors localized on the post-synaptic membrane of the muscle fibre's motor end plate, a specialized region.
Hence , the answer is ACh (acetylcholine) .
