The H-zone in the skeletal muscle fibre is due to
- the central gap between actin filaments extending through myosin filaments in the A-band
- extension of myosin filaments in the central portion of the A-band
- the absence of myofibrils in the central portion of A-band
- the central gap between myosin filaments in the A-band.
Answer
(1) the central gap between actin filaments extending through myosin filaments in the A-band
Solution
As per NCERT, in a relaxed muscle the edges of the thin (actin) filaments on either side of the thick (myosin) filaments partially overlap the free ends of the thick filaments, leaving the central part of the thick filaments.
⇒ This central part of the thick filament, not overlapped by thin filaments, is called the H-zone.
∴ The H-zone is due to the central gap between the actin filaments that extend into the A-band through the myosin filaments.
Answer: (1)