Question

The H-zone in the skeletal muscle fibre is due to:

• A. extension of myosin filaments in the central portion of the A-band
• B. the central gap between actin filaments extending through myosin filaments in the A band
• C. the central gap between myosin filaments in the A-band
• D. the absence of myofibrils in the central portion of A-band

Answer 1

The correct option is B the central gap between actin filaments extending through myosin filaments in the A band

‘A’ band and ‘I’ band are arranged alternatively throughout the myofibrils in the skeletal muscle fibre.

The A band (anisotropic band) also called the dark band has both thick myosin and thin actin filaments. However, in the centre of the A band, only thick myosin filaments are present and this region is called the H zone. The H zone appears somewhat lighter than the overlap region of the A band.

I band (isotropic band) also called the light band has only thin actin filaments.


Hence, the H-zone is the central gap between actin filaments extending through myosin filaments in the A band.

So, the correct answer is option C.