MUSCLE PHYSIOLOGY

Detailed explanation-1: -During muscle contraction, the I band is reduced in size as the overlap between the thick and thin filaments increases. The Z-lines come together, and so the sarcomere shortens as well.

Detailed explanation-2: -Upon muscle contraction, the A-bands do not change their length, whereas the I-bands and the H-zone shorten.

Detailed explanation-3: -Since during muscle contraction, the myosin filaments overlap the actin filaments, the I band diminishes in size because the region of overlap between the actin and myosin increases. The H-zone also diminishes and eventually disappears as the region of overlap between myosin and actin filament increases.