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Unformatted text preview: or 34C cold receptor 27C 21C warm cold dynamic response static response 27C 21C dynamic response static response Static Response (im mp/s) warm thermoreceptors cool thermoreceptors cold cold polymodal nociceptors nociceptors Static Response (im mp/s) nociceptor hot "paradoxical" nociceptors response hot Somatosensory Receptors Sustained response for static receptors: -Sharp cutoff for warm receptors at 45C -Dynamic response for receptors is wider cool -For extreme ranges: PAIN! thermoreceptors cold cold -Response by nociceptors polymodal
October 20, 2010 warm thermoreceptors 10 20 30 40 Skin Temperature (C) 50 60 nociceptors nociceptors hot nociceptor hot "paradoxical" nociceptors response Type 3: Nociceptors - Free nerve endings in skin or muscle, etc. = look the same10 thermoreceptors as 20 Nociceptors 11 30 40
Skin Temperature (C) 50 60 Free nerve endings in skin or muscle, etc.; look the same as Group A:# High-threshold mechanoreceptors = `prickling' pain (not excruciating) thermoreceptors. # # - Myelinated, large diameter Group A High-threshold Group: C:$ sensation mechanoreceptors; conveys `prickling'diameter - Unmyelinated, small pain 1) 1) polymodal nociceptors: respond to tissue injury (i.e. Polymodal nociceptors: respond to tissue injury = `burning' pain (excruciating) Group C: 2) acidity in many cases); `burning' pain have TRPV1 channels Heat pain afferents: 2) heat pain afferents; have TRPV1 channels 3) 3) freezing pain afferents afferents Freezing pain 4) 4) mechanical pain afferents afferents Mechanical mechano-insensitive; some 5) `sleeping' nociceptors;pain respond to histamine, mediate itch 5) `Sleeping' nociceptors: usually not active; mechano-INsensitive # # # # # some respond to histamine -> mediate itch (allergies) Separate populations of group C afferents conveying heat pain and mechanical pain. Hot -There are specialized nociceptors in group C -Sensory axons will terminate at diff layers in spinal cord (dorsal horn) -Heat nociceptors: start responding around 45C (weak initial response at ON line) -At 50C: stronger response (faster, more sustained firing rate)
Heat Nociceptor Warm 5 of 5
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This note was uploaded on 03/27/2012 for the course PSL PSL300 taught by Professor Mackayfrench during the Fall '11 term at University of Toronto.
- Fall '11