The vast majority of skeletal muscle fibers that are not found within muscle spindles at their polar ends and are innervated by alpha motoneurons. When stimulated by a motoneuron, actin filaments slide to overlap with myosin filaments, resulting in the muscle contracting.
See Actin, Alpha (α) motoneuron, Direct corticospinal connections or tracts, Gamma (γ) motoneuron, Intrafusal muscle fibers, Myosin, Motoneuron, Motor cortex, Motor unit, Muscle fiber, Muscle spindle, Sarcomere, Striated (or striped or voluntary) muscle, Type 1 muscle fibers, Type II muscle fibers, Ventral horn