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Nervous System, types of pain and pain pathways.
- 1. The Nervous Systemand Pain CHAPTER 7
- 2. What is Pain? An unpleasant sensory and emotional experience associated with actual or potential tissue damage. ◦ NOCICEPTION ◦ PAIN ◦ SUFFERING ◦ PAIN BEHAVIOR Pain is always subjective One of the body’s defense mechanisms - warns the brain that its tissues may be in jeopardy May be triggered without any physical damage to tissues. Acute pain is the primary reason people seek medical attention and the major complaint that they describe on initial evaluation Chronic pain can be so emotionally and physically debilitating that it is a leading cause of suicide.
- 3. The Nervous Systemand Pain Somatosensory System Brain Somatosensory Cortex Thalamus Spinal Cord Dorsal Horn Ventral Root PNS Afferent Neuron Efferent Neuron A-delta Fibers C-Fibers
- 4. PNS – NerveFiber Types Afferent – Sensory Neurons ◦ Three Types Are Important to Understand Pain A-delta fibers – smaller, fast transmitting, myelinated fibers that transmit sharp pain Mechanoreceptors – Triggered by strong mechanical pressure and intense temperature C-fibers – smallest, slow transmitting unmyelinated nerve fibers that transmit dull or aching pain. Mechanoreceptors – Mechanical & Thermal Chemoreceptors – Triggered by chemicals released during inflammation A-beta fibers – large diameter, fast transmitting, myelinated sensory fibers Efferent – Motor neurons
- 5. Spinal Cord Multipleascending and descending tracts of interneurons (connect afferent & efferent) Afferent Neurons – Enter to dorsal (back) side Efferent Neurons – Exit the ventral (front) side
- 6. Spinal Cord SpinalLayers ◦ Spinal grey matters divided into 10 layers Substantia Gelatinosa ◦ Composed of a layer of cell bodies running up and down the dorsal horns of the spinal cord ◦ Receive input from A and C-fibers ◦ Activity in SG inhibits pain transmission
- 8. The Brain Thalamus Somatosensory Cortex
- 9. Thalamus The sensory switchboardof the brain Located in the middle of the brain
- 10. Somatosensory Cortex •Area ofcerebral cortex located in the parietal lobe right behind the frontal lobe •Receives all info on touch and pain. •Somatotopically organized
- 11. Pain Pathways –Going Up Pain information travels up the spinal cord through the spino-thalamic track (2 parts) ◦ PSTT Immediate warning of the presence, location, and intensity of an injury ◦ NSTT Slow, aching reminder that tissue damage has occurred
- 12. Pain Pathways –Going Down Descending pain pathway responsible for pain inhibition
- 13. The Neurochemicals ofPain Pain Initiators ◦ Glutamate - Central ◦ Substance P - Central ◦ Brandykinin - Peripheral ◦ Prostaglandins - Peripheral Pain Inhibitors ◦ Serotonin ◦ Endorphins ◦ Enkephalins ◦ Dynorphin
- 15. Theories of Pain Specificity Theory ◦ Began with Aristotle ◦ Pain is hardwired Specific “pain” fibers bring info to a “pain center” ◦ Refuted in 1965 Gate Control Theory
- 16. Gate-Control Theory – RonaldMelzack (1960s) Described physiological mechanism by which psychological factors can affect the experience of pain. Neural gate can open and close thereby modulating pain. Gate is located in the spinal cord. ◦ It is the SG
- 17. Opening and Closingthe Gate When the gate is closed signals from small diameter pain fibres do not excite the dorsal horn transmission neurons. When the gate is open pain signals excite dorsal horn transmission cells
- 20. Three Factors Involvedin Opening and Closing the Gate The amount of activity in the pain fibers. The amount of activity in other peripheral fibers. Messages that descend from the brain.
- 21. Conditions that Openthe Gate Physical conditions ◦ Extent of injury ◦ Inappropriate activity level Emotional conditions ◦ Anxiety or worry ◦ Tension ◦ Depression Mental Conditions ◦ Focusing on pain ◦ Boredom
- 22. Conditions That Closethe Gate Physical conditions ◦ Medications ◦ Counter stimulation (e.g., heat, massage) Emotional conditions ◦ Positive emotions ◦ Relaxation, Rest Mental conditions ◦ Intense concentration or distraction ◦ Involvement and interest in life activities
- 24. Categories of Pain Pain can be categorized according to its origin: ◦ Cutaneous – Skin, tendons, ligaments ◦ Deep somatic - Bone, muscle connective tissue ◦ Visceral – Organs, cavity linings ◦ Neuropathic – Nerve pain By certain qualities ◦ Radiating ◦ Referred ◦ Intractable
- 25. Phantom Limb Pain Pain in a absent body part Very common in amputees Ranges from tingling top sensation to pain
- 26. Acute Pain ACUTE– Pain lasting for less than 6 months ◦ Highly correlated to damage ◦ Anxiety abates w/treatment ◦ De-activation often helpful
- 27. Chronic Pain Painlasting > 6 months ◦ Not correlated to tissue damage ◦ Learned/Reinforced ◦ Often associated w/psychopathology or coping problems ◦ More likely to abuse alcohol and drugs ◦ Leads to shutting down ◦ Typically does not respond to drugs very well ◦ Activity is the best medicine
- 28. Measuring Pain Physiological ◦Unreliable Self-report ◦ Behavioral observations ◦ Rankings ◦ Pain questionnaires ◦ Psych tests
- 29. Headaches Tension -Muscular ◦ Daily hassles and perfectionism predict frequency and duration of headaches (Hons & Dewey, 2004) Migraine – Muscular and vascular ◦ Neuroticism scores predict migraines for females, but not males. ◦ Abbate-Daga et. Al, (2007) 105 Migrane w/out aura vs. 79 health controls Migraine group greater than controls on Depression Anger management Overcontrol Harm-avoidance, persistence and lower in self-directedness
- 30. Back Pain 80%of US residents experience LBP Many causes, but only 20% have definite identification Burns (2006) ◦ Chronic LBP ◦ Induced anger and sadness Anger tightened LB muscles in CLBP not C Sadness did not have and effect No effect found in other muscles
- 31. MANAGING PAIN Medical andPsychosocial Approaches
- 32. Multiple Sites ofControl
- 33. Medical Treatments forPain Non-opiate Analgesics Act peripherally NSAIDS COX inhibitors Advil, Vioxx, Aleve Steroidal Drugs Suppress immune system Cortisone, Prednisone
- 34. Medical Treatments forPain Opiate Analgesics Act centrally via endogenous opiate system ◦ Short-acting ◦ Long-acting Problems ◦ Tolerance ◦ Dependence
- 35. Medical Treatments forPain Skin Stimulation Massage ◦ Great as an adjunct TENS ◦ Mixed results Acupuncture ◦ Effective for a number of types of pain ◦ Reduces the need for meds
- 36. Medical Treatments forPain Surgery Surgery to reduce pain ◦ Brain surgery – ablate thalamus ◦ For intractable pain (cancer) Surgery to restore function ◦ Surgery for merely pain relief should be avoided Back Carpal Tunnel
- 37. Psychosocial Interventions to ImproveCoping w/Pain Hypnosis Biofeedback Relaxation Training Behavior Modification Cognitive Therapy/CBT Multimodal Approaches
- 38. Relaxation Training Varietyof techniques utilizing relaxation, distraction and re-focusing Generally Effective and Cheap ◦ Progressive Muscle Relaxation ◦ Meditative Relaxation ◦ Mindfulness Meditation ◦ Guided Imagery
- 39. Behavior Modification Programs Selectively reinforce new and more adaptive coping behaviors ◦ Exercise ◦ Activities ◦ Communication In regards to pain - extinguish pain behavior
- 40. Cognitive Therapy/CBT CT= Reappraisal + Coping Skills and Emotional Expression … CBT = CT + Behavior Mod ◦ Inoculation Training (CBT) Conceptualization Skill acquisition and rehearsal Application and follow-through Overall CT & CBT Effective for many conditions ◦ Table in your book LBP Recurrent Abdominal Pain Rheumatoid Arthritis Many more