The neurotransmitter released at neuromuscular junctions, stimulating skeletal muscle contraction, is .

The neurotransmitter released at neuromuscular junctions, which stimulates skeletal muscle contraction, is acetylcholine (ACh). When a nerve impulse reaches the end of a motor neuron, acetylcholine is released into the synaptic cleft (the space between the neuron and the muscle fiber). This neurotransmitter binds to specific receptors on the muscle cell membrane (sarcolemma), leading to depolarization of the muscle cell.

This depolarization triggers a series of events that result in muscle contraction. Firstly, it opens voltage-gated sodium channels, allowing sodium ions to flow into the muscle cell, further depolarizing the membrane. This change in membrane potential spreads along the muscle fiber and triggers the release of calcium ions from the sarcoplasmic reticulum. Elevated calcium levels inside the muscle cell facilitate the interaction between actin and myosin, the two primary contractile proteins, leading to muscle contraction.

After the contraction, acetylcholine is broken down by the enzyme acetylcholinesterase in the synaptic cleft, effectively terminating the signal and allowing the muscle to relax. This precise mechanism ensures that muscle contractions occur smoothly and efficiently, allowing for coordinated movements.