Now, in the next several lectures we're going to basically discuss the details and the functionality of each one of these systems individually. In this lecture, we're going to focus on a terminology that we're going to need to know that we're going to come across in our discussion on the human nervous system. So let's discuss and define what a motor neuron is what a sensory neuron is, what an inter neuron is. 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.