Sarcomere

The sarcomere is the smallest functional and structural unit of striated muscle tissue, including skeletal and cardiac muscle. It is the basic contractile unit within a myocyte (muscle fiber) and is responsible for muscle contraction. Sarcomeres are highly organized, repeating segments found along myofibrils within muscle fibers. They enable contraction by allowing sliding interactions between actin and myosin. When stimulated by calcium ions, regulatory proteins expose binding sites on actin so that myosin heads can attach, hydrolyze ATP for energy, pull on actin ("power stroke"), then detach—shortening the sarcomere lengthwise. Mutations or dysfunctions in sarcomeric proteins can lead to diseases such as hypertrophic cardiomyopathy or muscular dystrophies.

Other names

Sarcomerum