Final answer:
A motor unit consists of an alpha motor neuron and the muscle fibers it innervates, playing a crucial role in muscle contraction.
Explanation:
Motor unit is defined as an alpha motor neuron and all the motor fibers it innervates within a muscle. It is the basic functional unit of muscle contraction, where a single motor neuron activates multiple muscle fibers. Motor units differ in size, recruitment, and power, influencing muscle movement and strength.
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