The same thing goes for number two. We have motor unit number two that consists of motor neuron number one and the muscle cells that it controls. And the same thing is true for motor neuron number three. Motor neuron number three creates motor unit number three that consists of this neuron as well as the muscle cells that it actually controls. Now there are three things that actually affect the magnitude, the quantity of force that is produced by arrow muscles. So let's discuss what these three things are.