write a note on A-bands?
The A band is the region of a striated muscle sarcomere composed of myosin thick filaments with the length of approximately 1 μm. Its center is located at the center of the muscle sarcomere. In addition to myosin filaments, the A-band also contains actin thin filaments. This region is a comparatively dark area entirely within a sarcomere. The A-band does not shrink during muscle contraction.