Skeletal and smooth muscles move when nerve impulses sent from the blank stimulate the muscle fibers telling them to either contract or relax?

Skeletal and smooth muscles move when nerve impulses sent from the nervous system stimulate the muscle fibers, instructing them to either contract or relax. In skeletal muscles, this stimulation comes from motor neurons, while smooth muscle contraction is typically regulated by autonomic nerve fibers. These signals trigger a series of biochemical events that lead to muscle contraction and relaxation.