MUSCLE
SKELETAL MUSCLE
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Which of these options best summarizes the THIRD and final phase of a muscle contraction?
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A stimulus from the neuron reaches the muscle fiber and stimulates an action potential in the muscle.
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The action potential travels along the sarcolemma and penetrates into the muscle fiber. Calcium is released by the SR and travels to the sarcomere.
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The cross bridge cycle occurs after calcium is released by the SR. During this cycle, the actin myofilaments are pulled towards the M line by the myosin myofilaments.
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None of the above
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Explanation:
Detailed explanation-1: -The last phase is the relaxation phase, when tension decreases as contraction stops. Ca++ ions are pumped out of the sarcoplasm into the SR, and cross-bridge cycling stops, returning the muscle fibers to their resting state.
Detailed explanation-2: -In a concentric contraction, the muscle tension rises to meet the resistance then remains stable as the muscle shortens. During eccentric contraction, the muscle lengthens as the resistance becomes greater than the force the muscle is producing.
Detailed explanation-3: -There must be a neural stimulus. There must be calcium in the muscle cells. ATP must be available for energy.
There is 1 question to complete.