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Somatosensory System and Pain

פיסיולוגיה מורחב 08-9. Somatosensory System and Pain. lecture 2: Stimulus transduction and encoding. Prof. Marshall Devor, Ph.D. Dept. of Cell & Animal Biology and Center for Research on Pain Institute of Life Sciences Hebrew University of Jerusalem. "psychophysics".

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Somatosensory System and Pain

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  1. פיסיולוגיה מורחב 08-9 Somatosensory System and Pain lecture 2: Stimulus transduction and encoding Prof. Marshall Devor, Ph.D. Dept. of Cell & Animal Biology and Center for Research on Pain Institute of Life Sciences Hebrew University of Jerusalem

  2. "psychophysics" stimulus (physical units)  neural representation (1,2,3,4) 4 perception 3 early processing 2 nerve transmission 1 transduction & encoding

  3. evolution • bacteria, protozoa (tropism) • separation of sensation and effect • sensation  response (effector organ)  perception (information, emotional/affective vector) planerian סנדלית

  4. 2° sensory neuron 1° afferent regional functions of sensory neuron dorsal root ganglion nerve sensory receptor ending

  5. Receptive field • modality • location/space • dynamics

  6. Sensory processing • disaggregation • reassembly • binding • perception • action/ memory • location • mosaic • dermatome

  7. Transduction and encoding occur in the region of the sensory ending התמרה, קידוד

  8. exceptions: vision, olfaction audition vestibular sense taste specialized sensory transduction cell pain vibration touch itch proprioception

  9. transduction molecules anterograde axoplasmic transport

  10. How does transduction occur ? התמרה

  11. mechanoreceptor channels

  12. mechanoreceptor channels

  13. 0 mV generator potential (generator depolarization) generator current -60 mV

  14. ligand-gated receptors (some are channels) mechano-gated channels thermal-gated channels

  15. receptor types/ sensory transduction: mechanical, thermal (<, >), chemical receptor cells vs. receptor molecules mechanical: C.elegans – DEG/ENaC, drosophila – TRPn, painless vertebrates ? thermal: heat - TRPV1, TRPV2, TRPV3 (vanilloid, capsaicin) cold - menthol-R TRPM8 chemical: capsaicin – TRPV1 garlic, mustard – TRPA1 histamine H1,H2 ASICs (acid sensing ion channels) BK-Rs (bradykinin) PG-Rs (prostaglandins) etc.

  16. capsaicin receptor cloned (by D.Julius & M.Caterina et al. Nature ‘97) (cDNA from rodent DRG injected into HEK cells, screen for >Ca 2+ fluorescence on capsaicin application) vanilloid-R1 V1 • by sequence homology very similar to • drosophila “transient receptor potential” • channel TRP • TRPV1 • TRP receptor family…TRPVs, TRPAs, TRPMs, TRPCs

  17. TRPV1: sensitive to capsaicin, protons (pH), heat, some endocannabinoid lipids

  18. from stimulus to impulse train… transduction spike encoding

  19. Pacinian corpuscle

  20. stimulus encoding

  21. vibration, texture adaptation vs. habituation

  22. Dynamic response of sensory receptors frequency tuning curve SA RA Pacinian corpuscle sensitivity 0 100 300 Hz

  23. firing frequency stimulus intensity Intensity scaling • dynamic range • LTM vs. nociceptor • "threshold" • encoding region • saturation WDR

  24. firing frequency stimulus intensity Intensity scaling LTM nociceptor

  25. firing frequency stimulus intensity Intensity scaling LTM nociceptor

  26. from stimulus to impulse train… • 1. force transmission to • sensory ending • transduction • spike encoding

  27. Stimulus transmission viscoelastic properties of skin

  28. Stimulus transmission viscoelastic properties of skin

  29. Stimulus transmission viscoelastic properties of skin hair shaft corpuscular endings muscle spindles blood flow (thermal) hair shaft

  30. Stimulus transmission viscoelastic properties of skin hair shaft corpuscular endings blood flow (thermal) muscle spindles muscle spindle כישור השריר

  31. RA SA RA Variety of sensory endings (to code stimulus intensity, quality, dynamics) 1. force transmission to sensory ending 2. transduction 3. spike encoding

  32. Variety of sensory endings A: LTMs: SA, RA, PC, hair A: warming, cooling, down hair, mechano-nociceptors C: mechanical nociceptors mechano-heat nociceptors CMH polymodal nociceptors silent (sleeping) nociceptors

  33. פיסיולוגיה מורחב Somatosensory System and Pain lecture 2: Sensory transduction and encoding Prof. Marshall Devor, Ph.D. Dept. of Cell & Animal Biology and Center for Research on Pain Institute of Life Sciences Hebrew University of Jerusalem

  34. Receptive Field sensory processing disaggregation reassembly binding perception action/ memory

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