Pain is defined as an “unpleasant emotional experience usually initiated by a noxious stimulus and transmitted over a specialized neural network to the central nervous system where it is interpreted as such”. Free nerve endings – responsible for carrying noxious stimulus from both superficial as well as deep somatic and visceral pain sensations therefore reffered as nociceptors According to type of impulses they carry second order neuron can be classified as – LOW THRESHOLD MECHANOSENSORY( ligth touch, pressure and Proprioception) NOCIOCEPTIVE SPECIFIC ( Noxious stimulation) WIDE DYNAMIC RANGE ( wide range of stimulus intensities from nonnoxious to noxious. SILENT NOCICEPTORS (It is an afferent neuron that appear to remain or silent to any mechanical stimulation .These neuron become active with tissue injury and add to the nociceptive input entering the CNS.

1. Presenter – Dr Siddharth

2. • Introduction
• History
• Definitions
• Receptors of pain
• Neurotransmitters in pain sensation
• Theories of pain
• Neural pathway of pain
• Tracts of spinal cord
• Pathways of pain sensation
• Conclusion
• References

3. • Pain is defined as an “unpleasant emotional experience usually
initiated by a noxious stimulus and transmitted over a specialized
neural network to the central nervous system where it is interpreted as
such”.
Monhiem’s
• an unpleasant sensory and emotional experience associated with
actual or potential tissue damage, or described in terms of such
damage“
•
International Association For The Study Of Pain

4. NOCICEPTIO
N
PAIN
SUFFERIN
G
PAIN
BEHAVIOUR

7. FIELDS has
described that
the subjective
experience of
pain arises by
4 distinct
process
Transduction Transmission Modulation Perception

8. • Fig 2-2

12. • Free nerve endings – responsible for carrying noxious stimulus
from both superficial as well as deep somatic and visceral pain
sensations therefore reffered as nociceptors

15. SENSORY NEURONS
First Order Second Order Third Order

19. • According to type of impulses they carry second order neuron can
be classified as –
• LOW THRESHOLD MECHANOSENSORY( ligth touch,
pressure and Proprioception)
• NOCIOCEPTIVE SPECIFIC ( Noxious stimulation)
• WIDE DYNAMIC RANGE ( wide range of stimulus intensities
from nonnoxious to noxious.
• SILENT NOCICEPTORS (It is an afferent neuron that appear to
remain or silent to any mechanical stimulation .These neuron
become active with tissue injury and add to the nociceptive input
entering the CNS.

22. Anterolateral spinothalamic tract

33. • Central pain
• Projected pain
• Referred pain

36. • 3 rules of referred pain
• Follows the trigeminal lamination pattern
• Rarely crosses midline
• If pain felt outside the nerve that mediates pain it is
generally felt cephalic to nerve that is upward towards
head not caudally.

39. • THEORIES OF PAIN
• Specificity Theory
• Pattern Theory
• Gate Control Theory

40. • SPECIFICITY THEORY
• DESCARTES 1664, MULLER 1840
• Pain occurs due to stimulation of specific pain receptors (nociceptors)
with transmission by nerves directly to the brain
• PATTERN THEORY
GOLDSCHEIDER – 1894-- stimulus intensity and central summation are
critical determinants of pain
• Particular patterns of nerve impulses that evoke pain are produced by
summation of sensory input within the dorsal horn of spinal cord

41. • Ronald Melzack and Patrick D. Wall-1965

44. • Endogenous morphine
• Enkephalin and endorphins
• Forms the basis of acupuncture and use of opiods

46. • Textbook Of Medical Physiology -Guyton & Hall
11thedition
• Essentials Of Medical Physiology -K. Sembulingam
5th Edition
• Textbook Of Local Anaesthesia-monheims
• Orofacial Pain- Okeson
• Textbook Of Physiology- A .K. Jain
• Sicher & Dubrauls Oral Anatomy

47. • Thank you