The Muscular System: Movement and Control

The muscular system includes over 600 skeletal muscles that produce movement, maintain posture, and generate heat. Muscles work in antagonistic pairs — as one contracts (agonist), the opposing muscle relaxes (antagonist).

Skeletal muscle is organized from individual muscle fibers (cells) into fascicles, which are grouped into whole muscles surrounded by connective tissue layers (endomysium, perimysium, epimysium).

Muscle contraction occurs through the sliding filament mechanism, where actin and myosin filaments slide past each other in response to calcium release triggered by nerve impulses.

Muscle actions are described by the movement they produce: flexion, extension, abduction, adduction, rotation, pronation, supination, and more. Understanding muscle origins, insertions, and innervation is essential for clinical anatomy.