What is the area of a sarcomere that contains only myosin called?

The area of a sarcomere that contains only myosin is referred to as the H zone. This region specifically represents the portion of the sarcomere where only thick filaments, composed of myosin, are present without any overlapping thin filaments (actin).

In the context of muscle contraction and sarcomere structure, the H zone becomes particularly relevant during contraction, as it decreases in size when the sarcomere shortens, showing the amount of overlap between the thick and thin filaments. Understanding the function of the H zone is important for grasping how muscles generate force.

The A band comprises the entire length of the thick filaments and includes areas where actin and myosin overlap, which distinguishes it from the H zone. The I band, on the other hand, consists only of thin filaments and is located on either side of the A band. The Z line marks the boundary of each sarcomere and serves as an anchor for the thin filaments. Thus, the H zone is specifically defined by the presence of myosin only, making it the correct answer.