Final answer:
The neurotransmitter responsible for stimulating skeletal muscle contraction when released by motor neurons is acetylcholine (ACh). It binds to receptors on the muscle fiber's motor end plate and triggers depolarization, leading to muscle contraction.
Step-by-step explanation:
The specific neurotransmitter that is released by motor neurons and stimulates skeletal muscle is acetylcholine (ACh). This neurotransmitter is crucial for the transmission of neural signals from the motor neuron to the muscle across the neuromuscular junction. When an action potential arrives at the synaptic terminal of a motor neuron, calcium influx triggers the release of acetylcholine into the synaptic cleft. Acetylcholine then binds to receptors on the muscle fiber's motor end plate, causing depolarization through the influx of sodium ions. This depolarization leads to an action potential in the muscle cell, ultimately resulting in muscle contraction.