MUSCLE PHYSIOLOGY

Detailed explanation-1: -The A-band which consists of the H zone contains actin and myosin filaments both. The reason for the H-zone of becoming lighter is that it only consists of myosin and no actin fibers which block the light passage and the dark M line also marked on each side of the H zone.

Detailed explanation-2: -Each sarcomere has a central A band made of thick myosin filaments and two half I bands made of thin actin filaments on either side of the thick filaments leaving the central part of the thick filaments. This central part of thick filament, not overlapped by thin filament is called H zone.

Detailed explanation-3: -The dark bands are called A bands while the light regions are termed I bands . The A bands are themselves striped, consisting of a lighter central band called the H zone (or AH zone) flanked by two darker regions (AI zones).

Detailed explanation-4: -Thin filaments do not extend all the way into the A bands, leaving a central region of the A band that only contains thick filaments. This central region of the A band looks slightly lighter than the rest of the A band and is called the H zone.

Detailed explanation-5: -The H zone is in the center of the A band where there is no overlap between the thick and the thin filaments. Therefore, in the H zone, the filaments consist only of the thick filament.