Why are some nerve reactions staggered or delayed? Like when you stub your toe, and you have that first moment of pain, then kind of a pause, and then the pain really hits you. Or you stick your hands under water coming out of a sink that’s too hot, again you get the first moment of pain, a pause as you jerk your hands out from under the water, and then more pain hits you.
Is this a psychological effect, or are the nerves themselves doing this? Is it done as a survival mechanism, to give you a pain-free second to free yourself from the source of the pain before it incapacitates you?
The initial reaction to a potentially noxious stimulus (hot, sharp, etc) is a protective reflex response, requiring minimal higher cortical processing in order to effect a withdrawal response as rapidly as possible.
Higher cortical functions then process exactly what happened–what the exact stimulus was, whether it was dangerous, and so on. If you stub your toe, step on a nail, or get stung on the toe, the initial reflex is exactly the same–a rapid cessation of the original conscious motion of that area of the body and a reflexive withdrawal. It’s not so much to give you a pain-free second to free yourself from the source of the pain as it is a protective mechanism to avoid further injury while your brain processes what to do about the situation longer term. In the case of a noxious stimulus that persists–you actually burned your hand after touching something hot–the pain fibers continue to fire because the injury is persisting.
You might think of the pain-free window as the period of time when the brain is otherwise occupied with processing. In certain situations–say you break a bone in a life-and-death struggle–this period of time can be remarkably long and you may not notice a broken finger until some time later. Under extreme duress the brain can also release chemicals which ameliorate your short-term pain response and change the length of the window.