One nice example of the speed difference created by myelin: You know how when you stub your toe, your body gives you that one second of reflection time to think about what you just did and what you’re about to feel, before the pain actually kicks in? What’s happening is you feel both the sensation of your toe hitting against something and the sharp part of the pain right away, because sharp pain information is sent to the brain via types of axons that are myelinated. It takes a second or two for the dull pain to kick in because dull pain is sent via unmyelinated “C fibers”—at only around one meter/second.

https://waitbutwhy.com/2017/04/neuralink.html