HUMAN PHYSIOLOGY
LOCOMOTION AND MOVEMENT
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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I
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A
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H
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Z-line
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Detailed explanation-1: -The A-band encompasses the whole span of a single thick filament. The anisotropic band includes both thin and thick filaments. The A band which is present alternatively in the myofibrils stays untouched during the contraction and relaxation of skeletal muscles.
Detailed explanation-2: -Explanation: During muscular contraction, the myosin heads pull the actin filaments toward one another resulting in a shortened sarcomere. While the I band and H zone will disappear or shorten, the A band length will remain unchanged.
Detailed explanation-3: -The A band does not shorten-it remains the same length-but A bands of different sarcomeres move closer together during contraction, eventually disappearing.
Detailed explanation-4: -The Z-lines come together, and so the sarcomere shortens as well. However, the A band does not change length during muscle contraction, since its length is the same as the length of the thick filaments.
Detailed explanation-5: -Upon muscle contraction, the A-bands do not change their length i.e the length of A band remains constant. whereas the I-bands and the H-zone shorten. This causes the Z lines to come closer together.