Skeletal muscle

Skeletal muscle is striated muscle tissue usually attached to bones and controlled largely by the somatic nervous system. Its contractions produce movement, stabilize joints, and help maintain posture.

Neuromuscular junction: The synapse where a motor neuron communicates with a skeletal muscle fiber. Motor neurons initiate contraction by releasing acetylcholine at this specialized synapse.
Sarcomere: The repeating contractile unit of striated muscle, bounded by Z-discs. Sarcomeres arranged in series give skeletal muscle its striated appearance and shortening capacity.
Muscle hypertrophy: An increase in the size of muscle fibers that enlarges a muscle. Resistance training can enlarge skeletal muscle fibers through repeated loading and recovery.
Cardiac muscle: Striated muscle tissue that forms the heart and contracts rhythmically without voluntary control. Like skeletal muscle it is striated, but cardiac muscle is specialized for continuous pumping.
Excitation–contraction coupling: The process linking an electrical signal in a muscle cell to calcium release and contraction. It connects the muscle fiber's action potential to the calcium signal that enables force production.
Myosin: A motor protein that uses ATP to move along actin filaments. Myosin heads generate force by cycling against actin within skeletal muscle sarcomeres.
Muscle atrophy: A decrease in muscle size caused by loss of muscle protein and, often, muscle fibers. Disuse, denervation, and disease can reduce skeletal muscle mass and strength.
Smooth muscle: Nonstriated muscle tissue that controls many involuntary movements in internal organs and blood vessels. Its nonstriated structure and involuntary control contrast with skeletal muscle's typical organization.
Sliding filament theory: The model in which actin and myosin filaments slide past one another to shorten a muscle sarcomere. It explains how skeletal muscle fibers shorten without their contractile filaments themselves shrinking.
Actin: A protein that forms thin filaments and interacts with myosin in muscle contraction. Actin filaments provide the tracks that myosin pulls during contraction.

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