Final answer:
A large motor neuron can send fibers to control a vast number of muscle fibers, sometimes up to thousands, particularly in large muscles such as the quadriceps, which are involved in gross movements.
Step-by-step explanation:
A large motor neuron may send fibers to as many as thousands of muscle fibers. This is because the axons of motor neurons will branch to innervate multiple muscle fibers, forming what is known as a motor unit.
Motor units come in various sizes, and while some motor neurons may control as few as 10 muscle fibers in muscles that require high precision like extraocular muscles, others may control up to 1000 muscle fibers in large muscles like the quadriceps that are responsible for gross movements.
Larger muscles demanding powerful contractions will typically have motor units containing more muscle fibers.
The number of muscle fibers in a motor unit is proportional to the muscle's requirements for force and precision.
The primary motor cortex has a larger topographical field for muscles requiring finer control, which corresponds to a greater number of motor units for those muscles.
Conversely, large motor units in the thigh or back muscles can each innervate thousands of muscle fibers, allowing for strong, less precise movements like extending the knee.