ANATOMY

Detailed explanation-1: -Myosin forms filaments in an antiparallel fashion at the center of the thick filament, while myosin forms filaments in a parallel way in the rest of the thick filament. Consequently, a bipolar thick filament is formed, leaving a central bare zone in the middle.

Detailed explanation-2: -The thick filament, myosin, has a double-headed structure, with the heads positioned at opposite ends of the molecule. During muscle contraction, the heads of the myosin filaments attach to oppositely oriented thin filaments, actin, and pull them past one another.

Detailed explanation-3: -In striated muscle cells, myosin forms the backbone of the thick filaments, which are anchored within the M-band and extend bidirectionally toward the two opposite ends of the sarcomere (171, 247).

Detailed explanation-4: -Myofibrils Are Composed of Actin and Myosin Filaments Each myofibril (Figure 6-1D andE) is composed of about 1500 adjacentmyosin filaments and 3000actin filaments, which are large polymerized protein molecules that are responsible for the muscle contraction.

Detailed explanation-5: -Each sarcomere consists of a central A-band (thick filaments) and two halves of the I-band (thin filaments).