MUSCLE
SKELETAL MUSCLE
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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frequency of muscle contraction
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number of muscle cells being stimulated at one time
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duration of muscle contraction
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None of the above
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Detailed explanation-1: -As more and larger motor units are activated, the force of muscle contraction becomes progressively stronger. A concept known as the size principle, allows for a gradation of muscle force during weak contraction to occur in small steps, which then become progressively larger when greater amounts of force are required.
Detailed explanation-2: -Smooth and graded changes in force of contraction are achieved through summation of responses to successive stimuli and recruitment of motor units. Sustained muscle contraction requires de novo synthesis of ATP, which is principally aerobic or anaerobic depending on muscle fibre type.
Detailed explanation-3: -Stimulation of the muscle fibre, causes a wave of depolarisation to pass down the t-tubule, and the SR to release calcium ions into the sarcoplasm. Calcium is pumped back up into the SR to lower calcium ion concentration in the sarcoplasm, to relax the muscle (turn off contraction).