PHYSIOLOGY
MUSCLE CONTRACTION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Calcium’s purpose in muscle contraction is to
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cross the neuromuscular junction and stimulate the sarcolemma
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travel down the T-tubule to reach interior myofibrils
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bind to troponin, move tropomyosin, and expose actin’s binding sites
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attach to actin, forming a crossbridge
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Explanation:
Detailed explanation-1: -(1) Striated muscle in the relaxed state has tropomyosin covering myosin-binding sites on actin. (2) Calcium binds to troponin C, which induces a conformational change in the troponin complex. This causes tropomyosin to move deeper into the actin groove, revealing the myosin-binding sites.
Detailed explanation-2: -The molecular regulation of striated muscle contraction couples the binding and dissociation of Ca2+ on troponin to the movement of tropomyosin on actin filaments. In turn, this process exposes or blocks myosin binding sites on actin, thereby controlling myosin crossbridge dynamics and consequently muscle contraction.
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