Final answer:
Small muscles have fewer fibers as they often comprise small motor units that provide precise control, such as in extraocular muscles where each neuron innervates around six muscle fibers.
Step-by-step explanation:
Small muscles have a smaller number of muscle fibers compared to larger muscles. Muscles that require fine motor control, such as the extraocular muscles responsible for moving the eyeballs, have small motor units. In these muscles, each motor neuron supplies only about six or so fibers.
This precise innervation allows for fine control necessary for functions like focusing the eyes. In contrast, muscles that demand less precision but more power, such as the quadriceps, have motor units that can include up to 1000 muscle fibers. This larger number is suited for powerful contractions where precise control is less critical.
It's important to note that the size and number of muscle fibers in a motor unit correspond to the control and force required by that muscle. Therefore, the size of the motor unit is inversely related to the precision of movement that muscle performs.
The more delicate the required movement, the smaller the number of fibers in the motor unit. As such, muscles like those controlling eye movement or finger movements have many motor units with fewer muscle fibers to allow for precise control.