MICROANATOMY

Detailed explanation-1: -The light bands contain actin(thin filament ) and are called I-band or Isotropic band, whereas the dark band called ‘A’ or Anisotropic band contains myosin(thick filament).

Detailed explanation-2: -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.

Detailed explanation-3: -The dark A band consists of parallel myosin thick filaments, in a hexagonal arrangement in cross-section. The thick filaments of a single sarcomere are connected to each other by means of the M disc at their centres.

Detailed explanation-4: -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-5: -The thick and thin filaments overlap contain myosin to form dark bands called A bands. Alone, thin filaments form light bands, called I bands, and are made from actin. The spacing between Z-lines decreases and the width of the H and I-bands decreases also during muscle contraction.