WHY do you drop a hot potato long before you actually feel the pain that comes from burning your hand?
This is because as soon as you touched it your nerves sent a message to your spinal cord that said "too hot". The nerves in your spinal cord answered this message even before it reached your brain.
These nerves made you spread out your fingers so that you dropped the potato. You didn't even have to think about spreading your fingers because the reaction was automatic. This kind of movement is called a reflex action. -amazingfactsworld.com