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 FIRST 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: -A twitch occurs when one muscle fiber contracts in response to a command (stimulus) by the nervous system. The time between the activation of a motor neuron until the muscle contraction occurs is called the lag phase (sometimes called the latent phase).
Detailed explanation-2: -Muscle contraction occurs when the thin actin and thick myosin filaments slide past each other. It is generally assumed that this process is driven by cross-bridges which extend from the myosin filaments and cyclically interact with the actin filaments as ATP is hydrolysed.
Detailed explanation-3: -A single muscle twitch has three components. The latent period, or lag phase, the contraction phase, and the relaxation phase.
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