MUSCLE PHYSIOLOGY

Detailed explanation-1: -Thick and thin filaments, which comprise the myofilaments, are composed primarily of the proteins myosin and actin, respectively, and the light band of the sarcomere is the portion where only thin filaments are present and the dark band is where both thick and thin filaments are present.

Detailed explanation-2: -Thin myofilaments consists of actin, troponin and tropomyosin.

Detailed explanation-3: -Thin filaments are comprised of two actin strands, each harboring equally separated troponin complexes, which bind Ca2+ to move tropomyosin cables away from the myosin binding sites and, thus, activate systolic contraction.

Detailed explanation-4: -Thin myofilaments are 1 m long and 8 nm in diameter, consisting primarily of actin. Actin is a globular protein with a molecular weight of 43 kDa. Two F-actin strands twisted in a double helix form the backbone of the thin myofilament and possess a complementary binding site for the myosin globular head.