All motor units are not the same! Each muscle in the body includes many motor units. A motor unit consists of a group of individual muscle fibers that are activated by a single motor neuron. When stimulated by an action potential transmitted along the motor neuron, all the fibers in a motor unit develop muscle tension at the same time. But how do they vary? Motor units differ based on how quickly the motor unit develops muscle tension when stimulated and the resistance of the motor unit to fatigue. Which statement does not accurately describe an important difference between motor units? A) Fast twitch or type II motor units are used to help with posture and provide muscle tone. B) Fast twitch or type II motor units are employed to provide short bursts of higher muscle tension. C) Slow twitch or type I motor units develop a low peak force in a relatively long period of time and are resistant to fatigue. D) Type I motor units are very resistant to fatigue because they have an extensive blood supply to maintain aerobic respiration.