MICROANATOMY

Detailed explanation-1: -These bands correspond to the presence or absence of myosin filaments. The I bands contain only thin (actin) filaments, whereas the A bands contain thick (myosin) filaments. The myosin and actin filaments overlap in peripheral regions of the A band, whereas a middle region (called the H zone) contains only myosin.

Detailed explanation-2: -The thin filaments contain actin, tropomyosin, troponins C, I, and T and nebulin. The thick filaments are composed of myosin with the globular heads forming cross-bridges with thin filaments. Myosin-binding proteins, including MyBP-C, are associated with the thick filaments.

Detailed explanation-3: -Thin Filaments The thin filament contains several important contractile regulatory proteins (Figure 4). The main component is the actin filament, which is formed from the polymerization of globular actin molecules. Each globular actin monomer contains a binding site for the globular myosin head.

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.

Detailed explanation-5: -A sarcomere is composed of two main protein filaments (thin actin and thick myosin filaments) which are the active structures responsible for muscular contraction.