Presenter – Dr Siddharth

• 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

• 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

NOCICEPTION

PAIN

SUFFERING

PAIN BEHAVIOUR

FIELDS has described that the subjective experience of pain arises by

4 distinct process

Transduction Transmission Modulation Perception

• Fig 2-2

• Free nerve endings – responsible for carrying noxious stimulus

from both superficial as well as deep somatic and visceral pain

sensations therefore reffered as nociceptors

SENSORY NEURONS

First Order Second Order Third Order

• 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.

Anterolateral spinothalamic tract

• Central pain

• Projected pain

• Referred pain

• 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.

• THEORIES OF PAIN

• Specificity Theory

• Pattern Theory

• Gate Control Theory

• 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

• Ronald Melzack and Patrick D. Wall-1965

• Endogenous morphine

• Enkephalin and endorphins

• Forms the basis of acupuncture and use of opiods

• 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

• Thank you