Question

In a resting state of myofibril
1) thick filaments are entered into I-band
2) the edges of the thin filaments on either
side of the thick filaments partially overlap
the free ends of the thick filaments
3) the central part of the thick filaments are
overlapped by the thin filaments
4) H-zone is not visible due to overlapping of
thick and thin filaments

Answer 1

Answer:

Myofibril is made up of two types of filaments. They are thin filament(actin) and thick filament(myosin).

The light bands contain actin and are called I-band or Isotropic band, whereas the dark band called ‘A’ or Anisotropic band contains myosin. The ‘A’ and ‘I’ bands are arranged alternately throughout the length of the myofibrils.

In a resting state, the edges of thin filaments on either side of the thick filaments partially overlap the free ends of the thick filaments leaving the central part of the thick filaments. This central part of thick filament, not overlapped by thin filaments is called the ‘H’ zone.

Hence H-zone in skeletal muscle fibre is due to Central gap between actin filaments extending through myosin filaments in A-band.

So, the correct answer is 'Central gap between actin filaments extending through myosin filaments in A-band'.