Final answer:
The number of muscle fibers in a motor unit can range from about 10 for muscles requiring precise control to up to 1000 for large muscles that generate powerful contractions. Motor units and recruitment are fundamental for muscle function and control, allowing for varied muscle forces.
Step-by-step explanation:
The approximate range in number of muscle fibers for one motor unit varies greatly. For muscles requiring precision and fine control such as the extraocular muscles, a motor unit might only include around 10 muscle fibers. In contrast, for larger muscles like the quadriceps that are involved in producing powerful contractions, a motor unit might contain up to 1000 fibers. Motor units are critical for muscle function as they determine the precision of muscle control and are responsible for the recruitment process, which allows muscles to exert different forces for various tasks.
For instance, when picking up a feather using the biceps brachii arm muscle, small motor units are activated, providing minimal force. However, lifting a heavy weight will recruit large motor units, generating a much stronger contraction. This illustrates the nervous system's ability to control muscles through the recruitment of varied motor units, maintaining energy efficiency and preventing muscle fatigue.