Class 11 NEET Biology Locomotion and Movement

(d) : A striated muscle fibre is bounded by sarcolemma. It shows alternating dark and light cross bands, the striations. Dark band is called A band which has at its middle a light zone termed H zone. Light band is known as I band which is crossed through its centre by a dark membrane called Z line. The part of the muscle fibre between two successive Z lines functions as a contractile unit called sarcomere.