Hello Student ,

Thick and Thin filaments make up a dense part in sarcomere called A Band or Anisotropic band. It constitutes both actin and myosin fibrils and hence the word anisotropic.

It is a portion from one end of myosin filament to other . A lighter portion at the centre of A band is called the H zone and contains only thick filaments .

Hence A band is a region which has both Actin and Myosin filaments

Hope I was able to help.