Muscle movement occurs when muscles contract and relax, allowing the body to perform various actions. This process is controlled by the nervous system, which sends signals to the muscles through neurons. There are three types of muscles: skeletal, smooth, and cardiac. Skeletal muscles are responsible for voluntary movements, while smooth muscles control involuntary actions, such as digestion. When a muscle contracts, it shortens and pulls on the attached bones, creating movement at the joints. The energy for muscle contraction comes from ATP (adenosine triphosphate), which is produced during cellular respiration. This coordinated action enables activities ranging from walking to breathing.