ANATOMY

Detailed explanation-1: -Thick filaments are anchored in the middle of the sarcomere at the M-line. The I-band is the region on either side of a Z-disc that contains only thin filaments and titin.

Detailed explanation-2: -The H-zone contains only thick filaments. The A-band contains both thick and thin filaments and is the center of the sarcomere that spans the H zone. When the muscle contracts, the H-zone, I-band, the distance between Z-lines all become smaller, whereas the A band remains the same.

Detailed explanation-3: -H – zone is the central region of A band with only myosin filaments.

Detailed explanation-4: -The sarcomere consists of a bundle of myosin-containing thick filaments flanked and interdigitated with bundles of actin-containing thin filaments (Fig. 1). The striated appearance of muscle results from the alternation of thick-filament-containing (A-Band) and thin-filament-containing (I-band) regions.