Microneurography - Implementing Microneurography - Nociceptors

Nociceptors

Unmyelinated pain receptors known as nociceptors comprise the most numerous classes of somatic afferent nerve fibers. The majority of these are polymodal nociceptors which are activated by mechanical, thermal, and chemical stimuli. The activation of these receptors for heat corresponds to the heat pain threshold for humans. Unmyelinated nociceptor fibers that are not activated by mechanical stimulation are said to be mechano-insensitive. These fibers have been shown to differ from polymodal fibers in several ways including higher activation threshold for heat, larger innervation territories in the leg, slower conduction velocity, and greater activity dependent hyperpolarization. Mechano-insensitive nociceptors may become sensitized in several ways, sometimes resulting in chronic pain. Inflammatory mediators applied to receptors on “sleeping” mechano-insensitive fibers were found to sensitize the fibers and render them mechano-responsive. This finding may describe the increased sensitivity that results from an injury. It is suspected that the inflammatory mediators bind protein receptors on mechano-insensitive nociceptors but sensitization of these C-fibers may also be caused by changes in gene expression that affect expression of transduction proteins. In either case, the sensitization of mechano-insensitive nociceptors has been observed to result in hyperalgesia, chronic pain.

Read more about this topic:  Microneurography, Implementing Microneurography