The functional unit of a skeletal muscle is called a sarcomere. Sarcomeres are the repeating structural units within a myofibril, which is a component of the muscle fiber.
Each sarcomere is defined by the area between two Z discs (or Z lines), which serve as the boundaries. Within a sarcomere, the primary proteins responsible for muscle contraction—actin and myosin—interact in a highly organized manner. Actin filaments are thin, while myosin filaments are thick, and their overlapping arrangement allows for the contraction mechanism known as the sliding filament theory.
During muscle contraction, myosin heads pull on the actin filaments, causing them to slide past one another and shorten the sarcomere. This process occurs throughout many sarcomeres in a muscle, leading to the overall contraction of the muscle itself.
Understanding the structure and function of the sarcomere is crucial for comprehending how skeletal muscles operate and generate force, making it a key concept in muscle physiology.