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. And let's begin with bullet point number one, the size of the motor unit. Now what do we mean by the size of the motor unit? So earlier we said that a single motor unit can consist of thousands of muscle cells.