question_answer

The muscle band that remains unchanged during contraction and relaxation of the skeletal muscle is

A)  1                                            

B)  H

C)  A                                           

D)  A line

E)  H and Z line

Correct Answer: C

Solution :

                Muscle fibre shows transverse striations as alternate dark A (anisotropic) and light I (isotopic) bands. Z line (dense) is present at the centre of  band. It is called as Krauses membrane, with divides myofibrils into functional unit called sarcomeres. H-Zone is found at the centre of A band. M-line o rHensens line is the middle of H zone. During contraction and relaxation of muscles, both I band and H zone progressively shorten and disappears. So dark A band (anisouopic) undergo no change during contraction and relaxation of muscle fibres.