MEDICAL PHYSIOLOGY

Detailed explanation-1: -Tropomyosin is a fibrous protein that binds lengthwise along the groove of actin filaments . In striated muscle, each tropomyosin molecule is bound to troponin, which is a complex of three polypeptides: troponin C (Ca2+-binding), troponin I (inhibitory), and troponin T (tropomyosin-binding).

Detailed explanation-2: -During contraction, the interaction of myosin heads with the actin filaments pulls the thin filaments toward the center of the sarcomere.

Detailed explanation-3: -Thin filaments, are 7 nm in diameter, and consist primarily of the protein actin, specifically filamentous F-actin.

Detailed explanation-4: -A sarcomere is the basic contractile unit of a myocyte (muscle fibre). A sarcomere is composed of two main protein filaments (thin actin and thick myosin filaments) which are the active structures responsible for muscular contraction.

Detailed explanation-5: -As the actin is pulled, the filaments move approximately 10 nm toward the M line. This movement is called the power stroke, as it is the step at which force is produced. As the actin is pulled toward the M line, the sarcomere shortens and the muscle contracts.