szarkoméria

Szarkoméria is a term used in biology, specifically in the study of muscle structure, referring to the basic contractile unit of striated muscle. It is the repeating segment of myofibrils, the long protein filaments that run parallel to the muscle fiber. The organization of actin and myosin filaments within the sarcomere is responsible for the characteristic striated appearance of skeletal and cardiac muscle.

Each sarcomere is defined by its boundaries, known as Z-lines or Z-discs. These Z-lines anchor the thin filaments, which are primarily composed of actin. The thick filaments, made of myosin, are located in the center of the sarcomere, overlapping with the thin filaments. The interaction between actin and myosin, driven by the hydrolysis of ATP, causes the filaments to slide past each other, resulting in muscle contraction.

Key regions within a sarcomere include the A band, which corresponds to the length of the thick filament, and the I band, which contains only thin filaments. The H zone is the central region of the A band where there is no overlap between thick and thin filaments in a relaxed muscle. During contraction, the Z-lines are pulled closer together, shortening the sarcomere and thus the entire muscle fiber. The precise arrangement and sliding of these filaments allow for the generation of force and movement.