What is a motor unit?
1 Answer
Within a muscle, the muscle fibers are functionally organized as motor units. A motor unit consists of a single motor neuron and all of the muscle fibers it innervates.
The size of the unit can involve only a few fibers for fine movement to huge numbers for gross movement such as what occurs in walking.
The force generated by muscles to lift a feather is much less than the force required to lift a 25-pound weight. The force of contraction produced by a muscle is increased in two ways: multiple motor unit summation, which involves increasing the number of muscle fibers contracting, and multiple-wave summation, which involves increasing the force of contraction of the muscle fibers.
Therefore instead of responding in an all-or-none fashion, the entire muscle responds to stimuli in a graded fashion, which means that the strength of the contractions can range from weak to strong.
