Final answer:
Correct option: c. causes synaptic vesicles to fuse to the membrane of axon terminal, allowing release of acetylcholine. When acetylcholine is released into the synaptic cleft, it causes the fusion of synaptic vesicles to the membrane of the axon terminal, allowing the release of acetylcholine. This acetylcholine then binds to receptors on the sarcolemma, initiating a depolarization that propagates along the sarcolemma and T tubules. The depolarization leads to the release of calcium ions from the terminal cisternae of the sarcoplasmic reticulum, triggering muscle contraction.
Step-by-step explanation:
When an action potential reaches the axon terminal of a motor neuron, it depolarizes the membrane and opens voltage-gated calcium (Ca²+) channels. The influx of Ca²+ ions triggers a signaling cascade that causes synaptic vesicles containing acetylcholine (ACh) to fuse with the presynaptic membrane, allowing the release of ACh into the synaptic cleft. From there, ACh diffuses across the synaptic cleft and binds with ACh receptors on the sarcolemma of the muscle fiber, initiating depolarization. This depolarization spreads along the sarcolemma, creating an action potential which propagates along the T tubules and leads to the release of Ca²+ ions from the terminal cisternae of the sarcoplasmic reticulum, ultimately triggering muscle contraction.