Introduction The primary contractile unit of skeletal muscle is the sarcomere Skeletal and cardiac muscle contraction is explained by the sliding filament theory with four key steps login to view 4 more bullets Requirements for contraction login to view 3 more bullets Definitions login to view 2 more bullets Sarcomere Structure One sarcomere is defined as the segment between two Z-lines Important defining structures login to view 15 more bullets Important proteins login to view 17 more bullets Sliding Filament Theory An action potential triggers calcium release from the sarcoplasmic reticulum Calcium ions bind to troponin, inducing a conformational change in the troponin-tropomyosin complex login to view 2 more bullets Contraction login to view 15 more bullets