Despite
the fact that the same amount of activating Ca 2+ ions is released in each case, the size of a single skeletal muscle twitch is about 4
times smaller than a fused tetanus. Which ONE of the following
statements BEST describes why this is so? (Lecture: skeletal muscle, Chapter: force regulation)

Question

Despite
the fact that the same amount of activating Ca 2+  ions is released in each case, the size of a single skeletal muscle twitch is about 4
times smaller than a fused tetanus. Which  ONE  of the following
statements  BEST  describes why this is so? (Lecture: skeletal muscle, Chapter: force regulation)

Answer

The amplitude of the action potentials coming from the motor neuron is larger during a tetanus.

Answer

In a twitch (which occurs when a muscle is activated by a single action potential) there is not enough time to take up all the elastic tension before the muscle starts to relax again.

Answer

The myosin heads move more slowly during a twitch.

Answer

The CaATPase   pumps on the sarcoplasmic reticulum work faster during a single twitch, lowering the calcium concentration more quickly than in the case of the larger tetanus.

Answer

The rate of diffusion of Ca 2+  molecules from the sarcoplasmic reticulum to the contractile proteins is slower during a single twitch.

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