PHYSIOLOGY
SARCOMERE
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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increase
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decrease
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stay the same
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None of the above
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Detailed explanation-1: -During muscle contraction, the I band is reduced in size as the overlap between the thick and thin filaments increases. The Z-lines come together, and so the sarcomere shortens as well.
Detailed explanation-2: -The contraction of a striated muscle fiber occurs as the sarcomeres, linearly arranged within myofibrils, shorten as myosin heads pull on the actin filaments. The region where thick and thin filaments overlap has a dense appearance, as there is little space between the filaments.
Detailed explanation-3: -Thus when the muscle is fully contracted, the H zone is no longer visible. The I band contains only thin filaments and also shortens. The A band does not shorten-it remains the same length-but A bands of different sarcomeres move closer together during contraction, eventually disappearing.