PHYSIOLOGY
MUSCLE CONTRACTION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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T-Tubule of the Muscle Cell
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Sarcoplasmic Reticulum of the Muscle Cell
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The Sarcolemma of the Muscle Cell
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The interstitial space outside the muscle cell near the pre-synaptic terminal.
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Detailed explanation-1: -When calcium binds to troponin, the troponin changes shape, removing tropomyosin from the binding sites. The sarcoplasmic reticulum stores calcium ions, which it releases when a muscle cell is stimulated; the calcium ions then enable the cross-bridge muscle contraction cycle.
Detailed explanation-2: -The sarcoplasmic reticulum releases stores of calcium, which bind to troponin. This binding causes a conformational change in troponin that causes it to shift the position of the attached tropomyosin to uncover binding sites on actin. Myosin is then able to bind and contraction can occur.
Detailed explanation-3: -The calcium ions released from endoplasmic reticulum72) bind to the calcium-binding subunit of troponin (troponin-C (TnC), ∼18 kDa), and the inhibition by troponin is neutralized to trigger muscle contraction.
Detailed explanation-4: -(1) Calcium binds to troponin C, causing the conformational shift in tropomyosin that reveals myosin-binding sites on actin.