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PAIN

PAIN. Prof. Ashraf Husain. 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.

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PAIN

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  1. PAIN Prof. Ashraf Husain

  2. 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.

  3. CHARACTERISTICS OF PRIMARYAFFERENT 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

  4. CHARACTERISTICS OF PRIMARYAFFERENT FIBRES C – Fiber: • 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

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

  6. 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

  7. DORSAL HORN GATING MECHANISM

  8. A MODAL OF “GATING” OF PAIN

  9. Ascending Pathway

  10. Descending Analgesic Pathway

  11. ASCENDING AND DESCENDING PAIN PATHWAYS

  12. Neurotransmitters in Analgesic Pathway

  13. Referral of pain from the internal organs Organ Site of reffered pain • Meninges Back of head and neck • Heart Central chest arms (usually left), neck, occasionally abdomen. • Trachea Behind sternum • Diaphragm Shoulder tip • Oesophagus Behind sternum Cont…

  14. Organ Site of reffered pain • Stomach, duodenum Upper abdomen, epigastrium • Small bowel, pancreas Around umbilicus • Large bowel, bladder Lower abdomen above pubic bone

  15. VISCERAL PAIN

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

  17. CHARACTERSITICS OF VISCERAL PAIN • 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

  18. TERMS FREQUENTLY USED • 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.

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

  20. SITES & MECHANISM OF PAIN RELIEF

  21. Trans Coetaneous Electrical Nerve Stimulation (TENS)

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