Question

Physical training can lead to changes in muscle composition and properties of local motor neurons, both of which will alter our capabilities to carry out movements. Are the following statements about that type of plasticity of our motor system TRUE or FALSE?

While riding a bike, maintaining posture to keep sitting on the saddle is carried out by slow motor units, while the legs use fast fatigable motor units, while working really hard to get up a short steep incline very fast. Imagine you previously trained for lifting heavy weights and now train for running marathons, This leads to an increase in the excitability of the motor neurons, so that neurons start to become active with weaker stimulation. Due to the decreased excitability of motor neurons after training for heavy lifting, the muscle fibers they activate become active already when the task is to lift very light objects.   Unless your little pinky finger is trained to do heavy lifting, we can safely assume that the motor neurons that activate its muscles contact only very few muscle fibers. A motor neuron that has a relatively short duration of hyperpolarization (overshoot) after an action potential is expected to be able to produce higher action potential firing frequencies and thus stronger contractions of muscle fibers. A fast, large, strong, fast fatigable (FF) motor unit motor neuron that was trained to do heavy lifting has a very small axon diameter.

Answer 1

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While riding a bike, maintaining posture to keep sitting on the saddle is carried out by slow motor units, while the legs use fast fatigable motor units, while working really hard to get up a short steep incline very fast.      TRUE

Imagine you previously trained for lifting heavy weights and now train for running marathons, This leads to an increase in the excitability of the motor neurons, so that neurons start to become active with weaker stimulation.   FALSE

Due to the decreased excitability of motor neurons after training for heavy lifting, the muscle fibers they activate become active already when the task is to lift very light objects.  TRUE

Unless your little pinky finger is trained to do heavy lifting, we can safely assume that the motor neurons that activate its muscles contact only very few muscle fibers. TRUE

A motor neuron that has a relatively short duration of hyperpolarization (overshoot) after an action potential is expected to be able to produce higher action potential firing frequencies and thus stronger contractions of muscle fibers. FALSE

A fast, large, strong, fast fatigable (FF) motor unit motor neuron that was trained to do heavy lifting has a very small axon diameter. FALSE