What is the result of motor neuron stimulation in muscles?

When a motor neuron is stimulated, it releases acetylcholine at the neuromuscular junction, which then leads to an action potential in the muscle cell. This action potential travels along the muscle fiber and into the T-tubules, triggering the sarcoplasmic reticulum to release calcium ions.

The release of calcium ions is crucial because they bind to troponin, a regulatory protein on the actin filaments, which causes a conformational change that moves tropomyosin away from the binding sites on actin. This exposes the sites for myosin cross-bridging, allowing muscle contraction to occur through the sliding filament theory. Therefore, the result of motor neuron stimulation is the release of calcium ions from the sarcoplasmic reticulum, leading to muscle contraction.