-There are two main parts of the striation pattern of skeletal muscle fibers: * The light bands (I bands) are made up of tink filaments of actin attached to Z lines.*The dark bands (A bands) are made up of thick filaments of myosin that overlap thin filaments of actin.There are two main parts of the striation pattern of skeletal muscle fibers: * The light bands (I bands) are made up of tink filaments of actin attached to Z lines.