Twice burned

Why is it that when you prick your finger with a needle, for example, you feel the pain immediately and then it subsides, whereas when you run your hand under very hot water, you immediately feel the heat, followed by a "pause" for a half-second or so, and then there's what I'd call a "kick back", where you once again feel the heat but even more acutely? (Hope the description was clear enough so you know what I mean...)

When you break a bone, which I have, usually, but not always, your endorphins kick in, because the hurt overwhelms the "pain" system. After a while, the endorphins wear off and you *really* feel the pain. This is your body screaming that you have to *do* something about it. Even if you do nothing, the pain then subsides, because the body goes about its business of healing itself. In the case of a broken bone, the body is quite efficient, tho if you have not had it "set" properly, it will be deformed.

It is a good question. I hope I have answered it correctly, and ask any doctor skilled in this problem to correct me if I am wrong.

The principle difference seems to be that it takes a second or so for the damaging energy (heat) to move between the mediums (from the water to the nerve endings beneath the skin). If I remember my 8th grade Earth Science, water & organic materials are poor mediums for low-level heat transfer. Somebody back me up on that, please?

On the other hand, a pinprick doesn't really involve energy transfer, your nerve endings let you know what's going on the instant the pin touches them, at least according to my experiments. Anybody got some Bandaids?

Jd,

The body's pain numbing chemicals -not sure if it's endorphins, it could be- work for 20 minutes or more. Omni is referring to the very brief (1 or 2 seconds) period between when you spill the McDonalds coffee into your lap and the time you actually feel the pain. I've noticed this more than once, running my hand under the hot water tap, thinking it was cold. The sensation delay is particular to heat- I've noticed the same "pain delay" picking up a coffe cup that was a little too hot or pulling a bagel out of the toaster- it takes a moment before you have to drop it because it's too hot. I still stick to my slow heat transfer theory.

The pain delay could be caused by an "arc-reflex". You'd need to read a neurology text to get a full grasp of it, but basically, what happens is this:

1. You grab a hot pan.
2. The Neurons in your hand and arm "know" that you grabbed a hot pan.
3. The Neurons send a pain/heat message to your brain, AND they send a "let go of that hot pan, you nimrod" message to your hand.
4. You let go of the hot pan.
5. The pain rushes to your hand, followed shortly thereafter by endorphins and various other chemicals from the brain-soup.

What may be causing the pain-relief-pain sensation is the gap between when your hand knows that it's hurt and when your brain knows.