Let's define what the nucleus and the ganglia is with respect to our nervous system. Let's discuss pre ganglionic and post ganglionic neurons and then let's focus on a simple reflex arc. So let's begin with defining what a motor neuron is. A motor neuron is basically a neuron that begins within the central nervous system and then extends into the peripheral nervous system. And it basically carries an electric signal to some type of target cell. Usually the target could be an organ.