Question

During the muscle contraction, which zone decreases?

• A. I-zone
• B. Z-zone
• C. H-zone
• D. M-zone

Answer 1

The correct option is C H-zone

According to sliding filament theory, when a fibril contracts its A-bands remain intact, while the I-bands progressively shorten and eventually disappear. At this stage, H-zones also disappear because the active filaments of both the sides in each sarcomere may even overlap each other at the M-line and Z-lines touch the ends of myosin filaments.