PHYSIOLOGY
SARCOMERE
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Dies
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Disappears
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gets smaller
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Breaks down
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Detailed explanation-1: -When muscle contracts, the H zone (central region of Azone) which consists of thick filaments is shortened and the I band which contains only thin filaments is also shortened during the time of contraction.
Detailed explanation-2: -There is no change in the width of the A band, but both the I bands and the H zone almost completely disappear. These changes are explained by the actin and myosin filaments sliding past one another, so that the actin filaments move into the A band and H zone.
Detailed explanation-3: -As a sarcomere is shortened, the zone of overlap is reduced as the thin filaments reach the H zone, which is composed of myosin tails. Because it is myosin heads that form cross-bridges, actin will not bind to myosin in this zone, reducing the tension produced by this myofiber.