The muscular system is an organic system composed of skeletal, smooth and cardiac muscles. It allows body movement, maintains posture and circulates blood throughout the body. The muscular system of vertebrates is controlled by the nervous system, although some muscles can be completely autonomous. Together with the skeletal system, it forms the musculoskeletal system, responsible for the movement of the human body.MusclesThere are three distinct types of muscles: skeletal muscles, cardiac or cardiac muscles, and smooth muscles. Muscles provide strength, balance, posture, movement and heat to keep the body warm. Upon stimulation by an action potential, skeletal muscles perform a coordinated contraction by shortening each sarcomere. The best model proposed for understanding contraction is the sliding filament model of muscle contraction. Actin and myosin fibers overlap in a contractile movement toward each other. Myosin filaments have club-shaped heads that project toward the actin filaments. Larger structures along the myosin filament called myosin heads...