GENERAL HISTOLOGY

Detailed explanation-1: -The light bands are called I bands and contain only thin filaments. The dark bands are called A bands and contain thick and thin filaments, with the thick filaments running the entire length of the A band. Thus the length of the thick filament determines the length of the A band.

Detailed explanation-2: -The anisotropic band contains both thick and thin filaments. Within the A-band is a paler region called the H-zone (from the German “heller", brighter). Named for their lighter appearance under a polarization microscope.

Detailed explanation-3: -The sarcomere is the main contractile unit of muscle fiber in the skeletal muscle. Each sarcomere is composed of protein filaments (myofilaments) that include mainly the thick filaments called myosin, and thin filaments called actin. The bundles of myofilaments are called myofibrils.

Detailed explanation-4: -The myofibrils contain thick and thin filaments. The arrangement of thick myosin filaments along the myofibrils and the cell cause them to refract light and produce a dark band which is known as an A band. The anisotropic band is composed of both thick and thin filaments.