Final answer:
Fine control motor units involve a single motor neuron that innervates a small number of muscle fibers, allowing for precise movements particularly visible in the extraocular muscles for eye movement. They contrast with large motor units that control gross movements and require significant force.
Step-by-step explanation:
Fine control motor units consist of a single motor neuron that supplies a small number of muscle fibers. These units are essential for precise, delicate movements, such as those needed for eye movement or finger dexterity. The exemplary illustration of fine control can be seen in the extraocular muscles of the eyes, where each motor neuron innervates around six muscle fibers, enabling complex and highly coordinated eye movements needed for both eyes to focus swiftly on a single object.
Larger motor units are involved in more gross movements that require less precision and more force, such as those controlled by the thigh muscles for powerful actions like knee extension. Conversely, muscles requiring fine motor control contain more motor units and therefore occupy a larger area in the primary motor cortex. This intricate system allows for a wide range of muscle contractions, from the gentle grip necessary to hold a feather to the substantial force needed to lift heavy weights.