This document discusses somatic sensations including mechanoreceptive sensations like touch, pressure, and vibration. It describes kinesthetic sensations and proprioception. Thermoreceptive sensations like pain are also discussed. The pathways for pain sensation including Aδ and C fibers and the spinothalamic tract are summarized. Primary and secondary hyperalgesia are defined as changes in receptor sensitivity and central sensitivity due to tissue injury. The trigeminal pain pathway and factors that influence pain perception like the Lewis P factor are also briefly covered.

1. Gawad
Neuroscience Physiology
Lecture 6
Saturday, November 10, 2018 1

2. SOMATIC
SENSATIONS
Mechanoreceptive
sensations
Tactile
sensation
Pressure
sense
Vibration
sense
Itch and tickle
Touch
sensation
Crude touch Fine touch
Tactile
localization:
Tactile
discrimination
Stereognosis
Kinesthetic
sensations
(Proprioceptive
sensations)
Conscious
kinesthetic
sensation:
Unconscious
kinesthetic
sensations
Theremoreceptive
sensations
Pain
sensation.

3. SOMATIC
SENSATIONS
Mechanoreceptive
sensations
Tactile
sensation
Pressure
sense
Vibration
sense
Itch and tickle
Touch
sensation
Crude touch Fine touch
Tactile
localization:
Tactile
discrimination
Stereognosis
Kinesthetic
sensations
(Proprioceptive
sensations)
Conscious
kinesthetic
sensation:
Unconscious
kinesthetic
sensations
Theremoreceptive
sensations
Pain
sensation.

4. Saturday, November 10, 2018 4

5. Saturday, November 10, 2018 5
Mechanical pain
receptors
Thermal pain
receptors
Chemical pain
receptors
Intact tissue cell
Chemical
substance
Chemical
substance
Chemical
substance
Painful
stimulus TRP channels

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Mechanical pain
receptors
Thermal pain
receptors
Mechanical pain
receptors
Thermal pain
receptors
Chemical
substance
Chemical
substance

7. Saturday, November 10, 2018 7

8. Ventrolateral spinothalamic tracts
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9. Aδ
Dorsal H.
Cells
VPLNT
Neo-
spinothalamic
tract
Post
central
gyrus
of
parital
lobe

10. Aδ
Dorsal H.
Cells
VPLNT
Neo-
spinothalamic
tract
Post
central
gyrus
of
parital
lobe
Paleo-
spinothalamic
tract
C
Dorsal H.
Cells
ILNT
All part
of the
cerebral
cortex
RF
Perceived by
thalamus????

11. Saturday, November 10, 2018 11
• Longer lasting pain sensation
• Emotional unpleasant features

12. Trigeminal pain pathway
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Post
central
gyrus
of
parital
lobe
spinal
trigeminal
nucleus
Trigeminal
lemniscus

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Injured
area
Flare
Normal skin
1ry
2ry

15. Saturday, November 10, 2018 15
Mechanical pain
receptors
Thermal pain
receptors
Mechanical pain
receptors
Thermal pain
receptors
Chemical
substance
Chemical
substance

16. Saturday, November 10, 2018 16
Injured
area
Pain
receptors
Pain
receptors
Pain
receptors

17. Saturday, November 10, 2018 17
Pain
receptors
Pain
receptors
Pain
receptors
Injured
area
1ry hyperalgesia:
Lowering the
threshold of pain
receptors (sensitized
nociceptors)
(peripheral
senstization)
Flare
1ry

18. Saturday, November 10, 2018 18
1ry hyperalgesia 2ry hyperalgesia
Receptor sensitivity
Receptor (stimulus)
threshold
Central sensitivity
Central threshold

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Pain
receptors
Pain
receptors
Pain
receptors
Injured
area
Flare
1ry
Pain Normal skin
2ry
Central sensitization
Pain
receptors

20. Saturday, November 10, 2018 20
Mechanical pain
receptors
Mechanical pain
receptors
Mechanical pain
receptors
Chemical
substance
1ry hyperalgesia
2ry hyperalgesia

21. Saturday, November 10, 2018 21
1ry hyperalgesia 2ry hyperalgesia
Receptor sensitivity
Receptor (stimulus)
threshold
Central sensitivity
Central threshold

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24. Saturday, November 10, 2018 24
Lewis P factorLewis P factorLewis P factor

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Lewis P factor
Lewis P factor
Lewis P factor
Lewis P factor