PHYSIOLOGY
DIFFERENT TYPE AND STRUCTURE OF MUSCLE FIBERS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Which BEST describes the relationship between a myofibril and the sarcoplasmic reticulum?
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Myofibrils are each surrounded by a tubelike network of sarcoplasmic reticulum
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Sarcoplasmic reticulum are each surrounded by a tubelike network of Myofibrils
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Myofibrils are each surrounded by cylinder-shaped sarcoplasmic reticulum
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A fasicle of myofibrils is each surrounded in sarcoplasmic reticulum
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Explanation:
Detailed explanation-1: -The sarcoplasmic reticulum or SR membrane is a membranous network that surrounds the myofibrils and makes contact with the T-tubule at junctions called dyads. So-called “feet” structures join the junctional SR to the T-tubules. These consist of ryanodine receptors (RyR) which form a Ca2+ channel across the SR membrane.
Detailed explanation-2: -Upon depolarization, the sarcoplasmic reticulum releases calcium ions. The calcium ions bind to the troponin, changing the shape of the troponin-tropomyosin complex such that the actin binding sites are uncovered. As soon as myosin binds to actin, the cocked head of myosin releases sliding the actin fiber.
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