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 presynaptic terminal.
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Detailed explanation-1: -The sarcoplasmic reticulum is deep within the muscle cell, cause thats where the troponin are that need the calcium. It would simply take too long for the calcium from the outside of the cell to get to the troponin.
Detailed explanation-2: -Each heartbeat is triggered by a pulse of intracellular calcium ions which bind to troponin on the actin-containing thin filaments of heart muscle cells, initiating a change in filament structure that allows myosin to bind and generate force.
Detailed explanation-3: -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.