How many muscle fibers are found in an average motor unit?

The average motor unit typically consists of approximately 100 to 200 muscle fibers. This range allows for effective muscle contraction and coordination, as the motor neuron can influence multiple muscle fibers to contract in unison. The specific number can vary depending on the muscle's function and the specific demands placed upon it. For instance, muscles responsible for fine motor control, such as those in the hands, might have fewer fibers per motor unit, whereas larger muscle groups might have more.

Given this context, the choice that accurately reflects the average is 100-150 muscle fibers. This range allows for a balance of strength and coordination, essential for the tasks that muscles perform. The options above and below this range would not accurately represent what is typical for a motor unit, whether they involve smaller or larger numbers of muscle fibers.