ABSTRACT
Intentional movements are executed by skeletal muscles, muscle attached by tendons to the skeleton. Skeletal muscle fibers are formed by the fusion of numerous myoblasts, so each fiber is a syncytium, a multinucleated structure that functions as a single unit. Within each sarcomere are two types of protein filaments. Thin filaments are attached to the Z disc at each end of the sarcomere and extend towards the center, and thick filaments interdigitate between them. Calcium is an absolute requirement for skeletal muscle contraction. By binding to troponin it triggers a conformational change in the thin filament allowing the interaction between actin and myosin which powers contraction. Blockade of transmission at the neuromuscular junction (nmj) is used during surgery to produce relaxation of skeletal muscle. They are effective within 1 min of injection.
