Motor units A single motor neuron(a motor) and all (extrafusal) muscle fibers it innervates The physiological functional unit in muscle (not the cell All cells in motor unit contract synchronouslyMotor units ⚫ A single motor neuron (a motor) and all (extrafusal) muscle fibers it innervates ⚫ The physiological functional unit in muscle (not the cell) ◼All cells in motor unit contract synchronously