A delta fiber: Difference between revisions

Aδ fibers respond to temperature on both the noxiously cold and hot ends of the spectrum. For both extremes, there exists a temperature threshold at which receptors begin to respond. Two main classes divide Aδ fibers: Type I and Type II. Type I receptors have higher heat thresholds then Type II. Thus, Type II Aδ fibers likely act as a first response to dangerously high temperatures.<ref name="Basbaum" /> Mechanistically, temperatures above 43°C activate a receptor associated with Aδ fibers called transient receptor potential vanilloid subfamily, member 1 ([[TRPV|TRPV1]]) which subsequently [[Depolarization|depolarizes]] the neuron.<ref>{{Cite journal|last=Szallasi|first=Arpad|last2=Cortright|first2=Daniel N.|last3=Blum|first3=Charles A.|last4=Eid|first4=Samer R.|date=May 2007-05|title=The vanilloid receptor TRPV1: 10 years from channel cloning to antagonist proof-of-concept|url=http://www.nature.com/doifinder/10.1038/nrd2280|journal=Nature Reviews Drug Discovery|language=En|volume=6|issue=5|pages=357–372|doi=10.1038/nrd2280|issn=1474-1784|via=}}</ref> This depolarization is transmitted to the spinal cord where axons of Aδ fibers terminate on second-order neurons in the dorsal horn. These neurons relay the nociceptive signal to the brain (specifically the [[thalamus]] and the [[brainstem]]) for further processing.<ref name=":0" /> At the cold end of the spectrum, it is clear that a significant proportion of Aδ fibers plays a role in perceiving cold temperatures, but the mechanism and related receptors are currently up for debate. Temperatures at or below ~ 15°C are cited as the cold threshold for painful stimuli. However, the threshold for Aδ fibers specifically seems to be lower (less than 0°C).<ref>{{Cite journal|last=Simone|first=D. A.|last2=Kajander|first2=K. C.|date=April 1997|title=Responses of cutaneous A-fiber nociceptors to noxious cold|url=https://www.ncbi.nlm.nih.gov/pubmed/9114254|journal=Journal of Neurophysiology|volume=77|issue=4|pages=2049–2060|issn=0022-3077|pmid=9114254}}</ref>