Skeletal Muscle Contraction - Cross Bridge Cycle

This lesson includes an animated video lecture, downloadable images, quiz questions and a PDF

Muscle contraction is at the basis of all skeletal movements. 

Skeletal muscles are composed of muscles fibers which in turn are made of repetitive functional units called sarcomeres. 

Each sarcomere contains many parallel, overlapping thin (actin) and thick (myosin) filaments.

The muscle contracts when these filaments slide past each other, resulting in a shortening of the sarcomere and thus the muscle. This is known as the sliding filament theory. 

Cross-bridge cycling forms the molecular basis for this sliding movement.

  • Muscle contraction is initiated when muscle fibers are stimulated by a nerve impulse and calcium ions are released.  


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