pseudo-H zone

The pseudo-H zone is a region within the A band of a muscle sarcomere. It appears as a narrow, lightly stained area containing only thick filaments, without the cross bridges that extend toward the thin filaments in other parts of the A band. The A band itself is darker and contains thick filaments that partially overlap with thin filaments. The sarcomere, the area between two Z lines, is the fundamental unit of muscle contraction, and the sliding of thick and thin filaments past each other, rather than shortening, is key to muscle physiology.12