HUMAN PHYSIOLOGY
LOCOMOTION AND MOVEMENT
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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i zone
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A zone
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H zone
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O zone
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Detailed explanation-1: -H – Zone disappears. M – line and Z – line also come closer.
Detailed explanation-2: -The Z line attached to the actin filaments is also pulled leading to the shortening of the sarcomere. Hence, the length of the band A remains constant as its original length and the I-band shortens and the H-zone disappears.
Detailed explanation-3: -The H zone-the central region of the A zone-contains only thick filaments and is shortened during contraction. The I band contains only thin filaments and also shortens.
Detailed explanation-4: -At the centre of contractile unit, sarcomere, there is H zone. It is also at the centre of dark band/A band. The H zone disappears when actin filaments slide inside A band during contraction of myofibril.
Detailed explanation-5: -During muscle contraction, each sarcomere shortens, bringing the Z discs closer together. There is no change in the width of the A band, but both the I bands and the H zone almost completely disappear.