muscle structure and function

Muscles are made of bundles of tiny fibers called muscle cells, which contract or shorten to produce movement. These fibers contain proteins like actin and myosin that slide past each other during contraction. When the brain sends a signal, nerves activate the muscle fibers, causing them to contract and generate force. Muscles work in pairs—when one contracts, the other relaxes—to move bones and joints. They also help maintain posture, support organs, and generate heat. Overall, muscles convert electrical signals into mechanical force, enabling body movements and vital functions.