Nociceptor

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A nociceptor is a sensory receptor that sends signals that cause the perception of pain in response to potentially damaging stimulus. Nociceptors are the nerve endings responsible for nociception, one of the two types of persistent pain. When they are activated, nociceptors can trigger a reflex.

Nociceptors are found in external tissue such as skin, cornea and mucosa as well as in internal organs, such as the muscle, joint, bladder and gut.

Types and functions

There are several types of nociceptor and they are classified according to the stimulus modalities to which they respond:

  • thermal
  • mechanical, and
  • chemical

Some nociceptors respond to more than one of these modalities and are consequently designated polymodal. Other nociceptors respond to none of these modalities (although they may respond to stimulation under conditions of inflammation) and have thereby earned the more poetic title of sleeping or silent nociceptors (Kandel et al, 2000).

Thermal nociceptors are activated by noxious heat or cold, temperatures above 45°C and below 5°C (Kandel et al, 2000). Mechanical nociceptors respond to excess pressure or mechanical deformation. Polymodal nociceptors respond to damaging stimuli of a chemical, thermal, or mechanical nature (Kandel et al, 2000).

Together these nociceptors allow the organism to feel pain in response to damaging pressure, excessive heat, excessive cold and a range of chemicals, the majority of which are damaging to the tissue surrounding the nociceptor.

Nociceptors and spanking

Spanking results in pain by stimulating the mechanical nociceptors of the buttocks. It is uncommon for punishment purposes to stimulate the thermal or chemical nociceptors, as this comes with a much greater risk of causing serious and permanent damage, such as burn or chemical burns.

A rare example of the safe stimulation of chemical nociceptors is figging.


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