Final answer:
If the motor nerve produced no synaptic vesicles, there would be no release of acetylcholine into the synapse, preventing the depolarization of the sarcolemma and muscle contraction.
Step-by-step explanation:
Motor neuron axons connect to muscle fibers at a neuromuscular junction. This is a specialized synaptic structure at which multiple axon terminals synapse with the muscle fiber sarcolemma. The synaptic end bulbs of the motor neurons secrete acetylcholine, which binds to receptors on the sarcolemma. The binding of acetylcholine opens ligand-gated ion channels, increasing the movement of cations across the sarcolemma. This depolarizes the sarcolemma, initiating muscle contraction. However, if the motor nerve produced no synaptic vesicles, there would be no acetylcholine released into the synapse, resulting in no binding to the receptors on the sarcolemma. The absence of acetylcholine would prevent the depolarization of the sarcolemma and muscle contraction would not occur.