Download Stimulus transduction and encoding

‫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"
stimulus (physical units)  neural representation (1,2,3,4)
4 perception
3 early processing
2 nerve transmission
1 transduction & encoding
evolution
planerian ‫סנדלית‬
•
•
•
bacteria, protozoa (tropism)
separation of sensation and effect
sensation  response (effector organ)
 perception (information,
emotional/affective vector)
regional functions
of sensory neuron
2° sensory
neuron
dorsal
root
ganglion
nerve
1° afferent
sensory
receptor
ending
Receptive field
• modality
• location/space
• dynamics
Sensory processing
• disaggregation
• reassembly
• binding
• perception
• action/ memory
location
• mosaic
• dermatome
Transduction and encoding occur in the
region of the sensory ending ‫ קידוד‬,‫התמרה‬
exceptions: vision, olfaction
audition
vestibular sense
taste
pain
vibration
touch
itch
proprioception
specialized sensory
transduction cell
transduction molecules
anterograde axoplasmic transport
How does transduction occur ?
‫התמרה‬
mechanoreceptor channels
mechanoreceptor channels
0 mV
-60 mV
generator potential
(generator depolarization)
generator current
mechano-gated channels
thermal-gated channels
ligand-gated receptors
(some are channels)
receptor types/ sensory transduction:
mechanical, thermal (<, >), chemical
mechanical:
receptor cells
vs.
C.elegans – DEG/ENaC,
receptor
drosophila – TRPn,
painless molecules
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.
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
TRPV1: sensitive to capsaicin, protons
(pH), heat, some endocannabinoid lipids
from stimulus to impulse train…
transduction
spike encoding
Pacinian corpuscle
stimulus
encoding
vibration, texture
adaptation vs. habituation
Dynamic response of sensory receptors
frequency
tuning curve
SA
RA
Pacinian corpuscle
sensitivity
0
100
300
Hz
dynamic range
• LTM vs. nociceptor
 "threshold"
 encoding region
 saturation
firing frequency
Intensity scaling
WDR
stimulus intensity
firing frequency
Intensity scaling
LTM
nociceptor
stimulus intensity
firing frequency
Intensity scaling
LTM
nociceptor
stimulus intensity
from stimulus to impulse train…
1. force transmission to
sensory ending
2. transduction
3. spike encoding
Stimulus transmission
viscoelastic properties of skin
Stimulus transmission
viscoelastic properties of skin
hair shaft
Stimulus transmission
viscoelastic properties of skin
hair shaft
corpuscular endings
muscle spindles
blood flow (thermal)
Stimulus transmission
viscoelastic properties of skin
hair shaft
corpuscular endings
blood flow (thermal)
muscle spindles
muscle spindle
‫כישור השריר‬
Variety of sensory endings
(to code stimulus intensity, quality, dynamics)
1. force transmission
to sensory ending
2. transduction
3. spike encoding
RA
SA
RA
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
‫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
Somato-visceral sensation
Receptive Field
tissue
skin
deep (musculoskeletal, visceral, brain)
modality/ quality
touch (static-dynamic (vibration, movement))
thermal
chemical
sensory processing
disaggregation
signal processing
reassembly
quality
binding
intensity
perception
location
action/ memory
dynamics