1. Somatosensory System and Pain
פיסיולוגיה מורחב
Somatosensory System
and Pain
lecture 3: The primary somatosensory neuron
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. primary
sensory
neuron

3. from stimulus to impulse train…variety
1. force transmission
to sensory ending
transduction
spike encoding

4. primary
sensory
neuron

5. neural crest
neural crest

6. Primary sensory neurons are pseudounipolar
growth cone
bipolar
sensory
ending
pseudounipolar

7. A C A

8. CGRP peptide neurotransmitter RT97 neurofilament
100 uM

10. Theory of "target derived
neurotrophism"

11. Matsuda et al

12. no synaptic contacts in DRG

14. numerous neurotransmitter and other receptor types
microvilli on DRG somata
enlarged surface area
numerous neurotransmitter
and other receptor types

16. primary
sensory
neurons

17. nociceptors

18. axon
epineurial
blood vessel
perineurium endoneurium
skin nerve muscle nerve m/sec
A, A Ia, Ib, II
A III
C (Remak bundle) IV

20. node of
Ranvier
internode
paranode
1-2 mm
nodal gap
2 um
Schwann cell
soma

21. myelin formation Schwann cell (glia) 30 um internode 1-2 mm
node of Ranvier 1-2 um

22. myelin formation
axon, myelin, Schwann cell, oligodendroglia

23. axon, myelin, Schwann cell

24. myelin formation in the CNS
Schwann cell vs.
oligodendroglial
cell

25. node of Ranvier

26. contactin
associated
protein

27. adult: DRG neuron
phenotype depends
on regulation of both
expression and traffic
of molecules of
excitability (NTs)

28. variety of primary afferent neurons
(stimulus encoding)
A: LTMs: SA, RA, PC, hair
A: warming, cooling, down hair,
mechano-nociceptors
C: mechanical nociceptors
mechano-heat nociceptors CMH
polymodal nociceptors
silent nociceptors

29. “neuronal phenotype” (correlates of sensory receptor types)
response CV
m/sec
axon
diam.
myelin
neurochem.
periph.morph. A
LTM
15-100
3-15m
heavy
glutamate
central morph. A
nociception
thermal
+LTM
2-15
1st pain
1-3 m
light
glutamate+
peptides
transduction
channels C
most
nocicept.
0.2-2
2nd pain
<1 m
none
peptides (NGF)
IB4 (GDNF)
electrogenic
spike
shape
TTX-S
TTX-R
neuro-
filam.
channel
distrib.
soma
diameter
surface
receptors
DRG peptides: SP, CGRP, NPY, NT, VIP, SOM, GAL, CCK…
substance P, calcitonin gene related peptide….

30. “neuronal phenotype” (correlates of sensory receptor types)
response CV
m/sec
axon
diam.
myelin
neurochem.
periph.morph. A
LTM
15-100
3-15m
heavy
glutamate
central morph. A
nociception
thermal
+LTM
2-15
1st pain
1-3 m
light
glut+
peptides
transduction
channels C
most
nocicept.
0.2-2
2nd pain
<1 m
none
peptides (NGF)
IB4 (GDNF)
electrogenic
spike
shape
TTX-S
TTX-R
neuro-
filam.
channel
distrib.
soma
diameter
surface
receptors
DRG peptides: SP, CGRP, NPY, NT, VIP, SOM, GAL, CCK…

31. Somatosensory System and Pain
פיסיולוגיה מורחב
Somatosensory System and Pain
lecture 3: The primary sensory neuron
Prof. Marshall Devor, Ph.D.
Dept. of Cell & Animal Biology and
Center for Research on Pain
Institute of Life Sciences
Hebrew University of Jerusalem

32. spike invasion and the safety
of through-conduction in DRG neurons
…. why are DRG neurons excitable ?

33. Conclusion: spike invasion is a design feature of
somatic
through-conduction
NEURON
simulation
spike invasion
Conclusion: spike invasion is a design feature of
DRG neurons… but to what end ??