The Region of the Sarcomere That Always Contains Only Thin

Question

The region of the sarcomere that always contains only thin filaments is the
A)Z line.
B)M line.
C)H band.
D)A band.
E)I band.

Accepted Answer

The thin filaments of actin are anchored to the Z line, and the distance between the Z lines defines the sarcomere. The I band is the region between two contiguous A bands, and only contains thin filaments. On the other hand, the A band contains both thick and thin filaments, whereas the H band only contains thick filaments, and the M band is the region in the middle of the H band where thick filaments are crosslinked. Therefore, the correct answer is E) I band.