work on muscle contraction

Muscle contraction occurs when tiny fibers called actin and myosin slide past each other, shortening the muscle. This process begins when the brain sends a signal, triggering the release of calcium ions inside the muscle cells. The calcium enables myosin to attach to actin and pull, using energy from ATP. This pulling action causes the muscle fibers to contract. When the signal stops, calcium levels decrease, and the fibers relax. This coordinated cycle of attachment, pulling, and releasing enables muscles to produce movement and force.