Read each question carefully and answer completely. a. (2 points) Which type of

Question

Read each question carefully and answer completely.

a.         (2 points) Which type of motor unit(s) (Slow, non-fatigueable or fast, fatigueable) is recruited during the generation of the weakest forces; the strongest forces? Explain.

b.         (2 points) Under normal conditions a single muscle cell, receiving a high frequency of action potentials from a single motor neuron will generate unfused tetani. How could a whole muscle provide smooth (non-twitchy) movements if unfused tetani were occurring in each of its muscle cells?

Explanation / Answer

a. Fast fatigable motor units recruited during the generation of the strong forces, because they utilize most of the energy at a little time to give maximum force.

Slow (oxidative) motor units generate weak force; these muscles utilize energy slowly, but generate consistent force.

b. A tetanic contraction occurs when a motor unit has been stimulated by its motor neuron at a maximum rate. This condition is the result of stimulation of motor unit by multiple impulses at a sufficiently high frequency. Each stimulus causes a twitch.

If these stimuli are slow enough then the tension in the muscle will relax between successive twitches. If stimuli are delivered at high frequency, then the twitches continue and results in the tetanic contraction.

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