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When you touch a hot object you first feel the touch and only after a second you feel the burn too, and if you detach your skin from the object the burn feeling continues for few seconds. I remember i've read something about why this occurs (something like 'burn neurons are slower than touch ones') but it's just a faded memory.

So i'd really appreciate your answers. Thanks in advance :).

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  • $\begingroup$ Well, a burn sensation typically will travel via a withdrawal reflex, which should be very quick since it doesn't need the brain to instruct movement. But I guess you're asking more about the perception/feeling of pain from the burn, which would need to travel o the brain. Is this true? $\endgroup$ – theforestecologist Mar 23 '17 at 17:08
  • $\begingroup$ Also, if something is truly hot enough to burn you, I really don't think there is a whole second delay between feeling it (via mechanoreceptors) and feeling the change in temperature (via thermoreceptors). $\endgroup$ – theforestecologist Mar 23 '17 at 17:08
  • $\begingroup$ Thanks for your comments. I know it's not a whole second delay but anyway the two responses aren't synced. I just remembered something else (maybe): it should be related to Na/K pump and the refractoy period. $\endgroup$ – Mirko Mar 23 '17 at 19:38
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    $\begingroup$ I think you might be thinking about the unmyelinated C-fibers which carry pain information and are slower? $\endgroup$ – Memming Mar 23 '17 at 19:44
  • $\begingroup$ Yes, thanks, I was looking for this. Anyway thanks to everyone, i appreciate that. $\endgroup$ – Mirko Mar 28 '17 at 17:05
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When you touch an object, a compression wave from the collision travels through your body at the speed of sound. A sensor at any depth in your skin can pick up that signal at roughly the same time as the collision.

When you touch a hot object, heat from it moves into your body via conduction and to some extent radiation. That heat flow moves much more slowly than the compression wave. It will take longer for the heat pulse to reach a sensor that is deep in the skin and raise the temperature by a sufficient amount to cause signalling.

There may be further differences in the sensory neurons or in the reaction to the signals. But there is a physical reason for the temperature signals to lag touch signals from the same object.

"Thermoception and Temperature Regulation" edited by J. Bligh, K. Voigt has some discussion of a study of thermoreceptors in rabbits. It suggests both that

  • signal latency increases with increasing depth in skin
  • while most receptors has short latency, some receptors had much greater latency, and that this disparity in response may aid in determining temperature gradients within the skin, not simply reading instantaneous skin temperature.
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