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A Protocol of Manual Tests to Measure Sensation and Pain in Humans
Published on: December 19, 2016
Unmyelinated afferents in human skin and their responsiveness to low temperature
1Facultad de Medicina, Clínica Alemana-Universidad del Desarrollo, Chile. mcampero@med.uchile.cl <mcampero@med.uchile.cl>
Abstract:
In humans, there are different types of cutaneous cold-sensitive afferents responsible for cold sensation and cold pain. Innocuous cold is primarily mediated by a population of slow A delta afferents, based on psychophysical and neurophysiological studies. Noxious cold (usually below 15 degrees C) is mediated, at least in part, by polymodal nociceptors. There is also a population of unmyelinated afferents responsive to innocuous low temperature, some of which also respond to heat, whose sensory function has not been completely defined. A paradoxical hot/burning evoked by cooling is unmasked by A-fibre block, and similar sensations are evoked by applying simultaneous cool and warm stimuli to adjacent skin areas. These unmyelinated fibres activated by innocuous cooling (and heating) may contribute to this hot/burning sensation, along with other thermoregulatory functions.
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