Melody, Joe is just saying that you display mainly small nerve damage because of your reaction to the heat and cold, the small nerves job is to interput the right temperature and send those signals to your brain, they can't when there damaged.
Myelinated nerve fibre wraps around the axon and becomes damaged and cannot send the proper signals to your brain, then its unmyelinated.
An axon is just the portion of a nerve cell that carries nerve impulses away from the cell body. A neuron typically has one axon that connects it with other neurons or with muscle or gland cells. Some axons can be real long, sometimes from the spinal cord down to a toe. Most axons of vertebrates are enclosed in a myelin sheath, which increases the speed of impulse transmission.
i hope this helps.
Brian