neurons are classified in two different ways they're classified either based on structure or based on function so let's take a look at the structural classification first there are three different types of neurons based on structure unipolar bipolar and multipolar and the way that these differ is just in the number of processes that are attached to the cell body unipolar has a single process bipolar two processes and multipolar more than two many in a unipolar neuron there is a single process that projects off of the cell body which you can see here the type of neuron that they're showing us is unipolar in our book sometimes other books will call this a pseudo-unipolar neuron and that's because that single process is branching another possibility is there are two processes that come off of the cell body this is known as bipolar and in a multipolar neuron you can see that there are many processes that come off of the cell body so anything more than two we would call it multipolar here we can see some variants between multipolar neurons bipolar neurons and unipolar neurons but regardless of what they look like all three of the structural types of neurons work in the same way so you can see in the multipolar neuron that there is a region that receives the incoming information a region that will generate and conduct the action potential and then a region that will convey that action potential to the next cell across the synapse uh in color coding using color coding same thing with bipolar there's going to be a region that receives the information generates and conducts the action potential conveys the action potential to the next cell and so on so bipolar unipolar and multipolar neurons even they look different they have the same parts and they work the same way a second way that we classify neurons is based on function and this has primarily to do with the direction of information flow if a neuron is carrying information into the central nervous system if it's contained within the central nervous system or if it's carrying information out of the central nervous system so let me show you what i mean when we look at the functional classification of neurons all we hear about is the direction of information flow so sensory neurons carry information into the central nervous system interneurons are completely contained within the central nervous system they don't project in or project out and then motor neurons carry information from the central nervous system out into the body so taking a closer look at these three types of neurons this is a sensory neuron it's bringing sensory information from the skin into the spinal cord here are some interneurons they have structures different from what we've looked at uh interneurons are just contained within the brain and spinal cord and so you can think of them as being like the internal wiring of the cns and here we can see a motor neuron carrying information from the spinal cord out to the body so trying to put this information together unipolar neurons are typically sensory neurons bringing information into the cns motor neurons are typically multi-polar neurons bringing information from the cns out to the body it would be great if interneurons were bipolar unfortunately that's not the case bipolar neurons are the most rare type of neuron in the body they're found in special senses like you can see here a row of bipolar neurons in the retina and interneurons don't look like these three structural categories and the interneurons are the most numerous and they make the internal connections in the brain and spinal cord