ANATOMY

Detailed explanation-1: -The A band contains thick filaments of myosin, which suggested that the myosin filaments remained central and constant in length while other regions of the sarcomere shortened. The investigators noted that the “I band, ” rich in thinner filaments made of actin, changed its length along with the sarcomere.

Detailed explanation-2: -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-3: -The dark band of the muscle sarcomere that corresponds to the thick myosin (protein) filaments. The A band is situated on either side of the H zone of a muscle sarcomere, that is the area where contraction and relaxation of the muscle occurs, where sarcomeres overlap during muscle movements.

Detailed explanation-4: -The arrangement of the thick myosin filaments across the myofibrils and the cell causes them to refract light and produce a dark band known as the A Band. In between the A bands is a light area where there are no thick myofilaments, only thin actin filaments. These are called the I Bands.

Detailed explanation-5: -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).