2. PAIN Prof. Ashraf Husain

3. 3 Classification of pain Pain perception is affected by the context in which it is experienced. Pain is arbitrarily categorized into somatic - superficial and deep - and visceral pain. Visceral pain is sometimes referred to another site. Structures to which the pain. is referred are innervated by the same spinal segment as the origin of the pain. Pain may arise from phantom limbs or be triggered by inappropriately mild stimulation in abnormal conditions.

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6. 6 CHARACTERISTICS OF PRIMARY AFFERENT FIBRES A δ Fiber: Myelinated - Diameter fine 2 - 5 μm 12 - 30 m/sec. conduction velocity Terminated at I and V layer Fast pain, rapid, pricking and well localized Neurotransmitter - Glutamate 20% pain conduction

7. 7 Non-Myelinated Diameter less than 2 f.lm.-0.5 to 2 m/s conduction velocity TeJrninate in I and n layers Slow, diffuse, dull, aching Neurotransmitter - P-Substance 80% of pain conduction CHARACTERISTICS OF PRIMARY AFFERENT FIBRES C – Fiber:

8. 8 TYPES: 1.HIGH TRHESHOLD MECHANORECEPTOR(HTM) NNERVATED BY - TIHN MYELINATED A FIBERS 2.POLYMODAL NOCICEPTORS(PMN) INNERVATED BY UNMYELINATED C FIBRES NOCICEPTOR: PAIN RECEPTOR

9. 9 DAMAGE AND INFLAMMATION RELEASE CHEMICAL MEDIATORS WICH ACTIVATE OR SENSITISE THE RECEPTOR ENDINGS CYTOKlNES BRADYKININ, PROSTAGLANDIN, P - SUBSTANCE RESULTS IN TRANSDUCTION CONDUCTION OF NERVE IMPULSE

10. 10 DORSAL HORN GATING MECHANISM

11. 11 A MODAL OF “GATING” OF PAIN

12. 12 Ascending Pathway

13. 13 Descending Analgesic Pathway

14. 14 ASCENDING AND DESCENDING PAIN PATHWAYS

15. 15 Neurotransmitters in Analgesic Pathway

16. 16 Referral of pain from the internal organs MeningesBack of head and neck HeartCentral chest arms (usually left), neck, occasionally abdomen. TracheaBehind sternum DiaphragmShoulder tip OesophagusBehind sternum Cont… OrganSite of reffered pain

17. 17 Stomach, duodenumUpper abdomen, epigastrium Small bowel, pancreasAround umbilicus Large bowel, bladderLower abdomen above pubic bone OrganSite of reffered pain

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19. 19 VISCERAL PAIN

20. 20 VISCERAL PAIN PATHWAY Pain - Aδ and fibers Travel with autonomic afferent Spinal cord (Dorsal Horn) Lat. spinothalamic tract Thalamus Somatosensory Cortex

21. 21 Poorly localized Associated with nausea and autonomic disturbance Often referred to another part of the body Cutting, crushing are not painful when applied to viscera Pain is caused by distension, ischemia and inflammation CHARACTERSITICS OF VISCERAL PAIN

22. 22 Hyperalgesia: Excessive Pain Allodynia: Pain caused by any other sensation e.g. touch will cause pain. Muscular Pain: Less blood flow in the muscles (ischemia). Stress analgesia: Mild degree of pain is not felt if the other part of the body has excessive pain. Causalgia: Burning pain. TERMS FREQUENTLY USED

23. 23 Thalamic Syndrome.Obstruction of the thalmogeniculate branch of the posterior cerebral artery Affects posterior thalamic nuclei.. Prolonged severe pain. TERMS FREQUENTLY USED

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25. 25 SITES & MECHANISM OF PAIN RELIEF

26. 26 Trans Coetaneous Electrical Nerve Stimulation (TENS)

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