MUSCLE PHYSIOLOGY

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: -An individual sarcomere contains many parallel actin (thin) and myosin (thick) filaments.

Detailed explanation-3: -An important feature of myosin polymerization is that myosin-II molecules are oriented in opposite directions in each half of the sarcomere. This orientation results in polarized thick filaments that help in directing force toward the center of the sarcomere.

Detailed explanation-4: -Most of the cytoplasm consists of myofibrils, which are cylindrical bundles of two types of filaments: thick filaments of myosin (about 15 nm in diameter) and thin filaments of actin (about 7 nm in diameter).