Function:

• Facilitates movement by contracting and relaxing muscles
• Maintains posture and body position
• Generates heat through muscle activity

Types of Muscles:

• Skeletal muscles: Attached to bones, responsible for voluntary movement
• Smooth muscles: Found in internal organs, involuntary contractions
• Cardiac muscle: Forms the heart, contracts rhythmically for continuous pumping

Muscle Structure:

• Muscle fibers contain myofibrils with actin and myosin filaments
• Motor neurons stimulate muscle contraction

Voluntary vs. Involuntary Control:

• Skeletal muscles under conscious control
• Smooth and cardiac muscles contract involuntarily

Muscle Contraction:

• Motor unit activation: Motor neuron and muscle fibers it controls
• Sliding filament theory: Actin and myosin filaments slide past each other during contraction

Common Muscular Disorders:

• Strains: Overstretching or tearing of muscles or tendons
• Sprains: Ligament injuries due to overstretching
• Muscular dystrophy: Genetic disorders causing progressive muscle weakness