PHYSIOLOGY
SYNAPTIC PHYSIOLOGY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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the distance between z-lines decreases
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the H-zone disappears
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the muscle shortens
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the distance between z-lines decreases, the H-zone disappears, and the muscle shortens
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Detailed explanation-1: -When (a) a sarcomere (b) contracts, the Z lines move closer together and the I band gets smaller. The A band stays the same width and, at full contraction, the thin filaments overlap. When a sarcomere shortens, some regions shorten whereas others stay the same length.
Detailed explanation-2: -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-3: -Since during muscle contraction, the myosin filaments overlap the actin filaments, the I band diminishes in size because the region of overlap between the actin and myosin increases. The H-zone also diminishes and eventually disappears as the region of overlap between myosin and actin filament increases.
Detailed explanation-4: -When a muscle contracts, the actin is pulled along myosin toward the center of the sarcomere until the actin and myosin filaments are completely overlapped. In other words, for a muscle cell to contract, the sarcomere must shorten. However, thick and thin filaments-the components of sarcomeres-do not shorten.