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How do A-fibres and C-fibres differ in the speed at which they carry temperature signals?
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Thermoreception
Warm-blooded animals, such as polar bears, maintain stable body temperatures and adapt to substantial geographic and seasonal temperature fluctuations. Thermal adaptation is supported by the function of sensory structures called thermoreceptors.
In the physiology of thermoreception, A-fibres and C-fibres differ significantly in their conduction speeds. Both warm and cold receptors are innervated by unmyelinated C-fibres, which conduct discharge activity very slowly. In contrast, cold receptors are also served by thinly myelinated A-fibres, which are capable of conducting impulses more rapidly than C-fibres.1
This difference in conduction speed is clinically observable; for instance, if peripheral nerve conduction is blocked by maintained pressure, sensations are interrupted in a specific order: first touch, then cold (mediated by the faster A-fibres), and finally warmth and pain (mediated by the slower C-fibres).1