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Q.
The muscle band that remains unchanged during contraction and relaxation of the skeletal muscle is
Locomotion and Movement
Solution:
'A' band is the region of striated muscle fibre that contains both thick (myosin) and thin (actin) filaments. It is visible as a dark band with a lighter central zone (H zone) in the middle of a sarcomere. During muscle contraction the thin actin myofilaments slide past the thick myosin filaments to penetrate deeper into 'A' band thereby shortening the I bands and sarcomere and also the muscle fibre. During relaxation the actin myofilaments slide back from $A$ bands thus elongating the sarcomere. Thus, A band remains unchanged during contraction and relaxation of the skeletal muscle.