Length of both anisotropic and isotropic band has changed.
The length of the thick and thin myofilaments has changed.
Length of the sarcomere remains same.
The myosin cross-bridges move on the surface of actin and the thin and thick myofilaments slide past each other.
Myosin cross bridges are the globular head of a myosin molecule. It projects from a myosin filament in muscle and in the sliding filament hypothesis of muscle contraction is held to attach temporarily to an adjacent actin filament and draw it into the A band of a sarcomere between the myosin filaments.