Final answer:
Muscles requiring fine motor control have a high innervation ratio, with motor neurons controlling fewer muscle fibers for precise movements, whereas gross motor control muscles like the quadriceps have a lower innervation ratio for powerful, less precise movements.
Step-by-step explanation:
Motor units are a central aspect of how the nervous system controls skeletal muscles. Motor units vary in size and are critical for different types of muscle functions; they include a motor neuron and all the muscles it innervates. Muscles that require fine motor control, such as the extraocular muscles controlling eye movement, have a high innervation ratio, meaning each motor neuron controls fewer muscle fibers, allowing for precise movements. On the other hand, muscles that are involved in gross motor control, like the large quadriceps muscle, have a lower innervation ratio where each motor neuron controls a larger number of muscle fibers, facilitating powerful but less precise movements.