The contraction of myocytes is governed by the sliding filament mechanism. In skeletal and cardiac myocytes, this process is initiated by the release of calcium ions from the sarcoplasmic reticulum in response to an action potential. Calcium ions bind to troponin, causing a conformational change in tropomyosin, which exposes myosin-binding sites on actin filaments. ATP-bound myosin heads then attach to these sites, pulling the actin filaments towards the center of the sarcomere, resulting in muscle contraction.
