Question: how fast do you get a message from the nerves if you touch something hot or cold

Pip Millington answered on 14 Nov 2016:

Messages (or action potentials) down sensory nerves travel at about 50 meters per second. If the distance between your fingers and your brain is about 1 metre, that means it takes about one fiftieth of a second (0.02s) for the nerve to transmit the message. However, it takes a bit longer because the receptors in the skin need to chemically transmit a message to the nerve, the nerve needs to send a chemical signal to another nerve in the base of the brain, and then your brain needs time to understand the message that something is hot and cold.

I can’t find any exact data on that right now but that probably takes closer to a second. By this time if something is very hot, you will have moved your hand out of the way because it’s a withdraw reflex. The sensory nerve cell acts directly upon a motor nerve cell to move your hand quickly so your don’t get burnt! That probably takes about a third to a half of a second and happens without your brain getting involved!

In other words, the nerves themselves carry messages very quickly; the bits in between the nerves are less quick!