Systems that cooperate in movement

In man (as an example of mammals) movement depends on three systems working together:

1. The skeletal system — provides the levers and a firm place for the muscles to attach; the joints allow the movement.
2. The muscular system — contracts and relaxes and so moves the bones.
3. The nervous system — sends the commands (nerve impulses) that make the muscles contract or relax.

If any system is damaged, movement is disturbed: broken bone, torn muscle, or damaged nerve each prevent normal movement.