sarcomereket

A sarcomere is the basic contractile unit of striated muscle tissue. It is the smallest component of skeletal and cardiac muscle that can contract. Sarcomeres are highly organized structures that repeat end-to-end along the length of a muscle fiber, forming myofibrils.

The sarcomere is characterized by its striated appearance, which arises from the arrangement of its protein filaments. The primary components of a sarcomere are the thick filaments, composed mainly of myosin, and the thin filaments, composed primarily of actin. These filaments are anchored to structures called Z-lines at either end of the sarcomere.

Within the sarcomere, several distinct regions are observable. The A band represents the full length of the myosin filaments, and it overlaps with the actin filaments. The I band contains only actin filaments and is bisected by the Z-line. The H zone is located in the center of the A band and contains only myosin filaments in a relaxed muscle. During muscle contraction, the myosin and actin filaments slide past each other, shortening the sarcomere. This sliding filament mechanism is the fundamental process of muscle movement. The precise arrangement and interaction of these proteins within the sarcomere are crucial for generating force and enabling locomotion.