HealthPsychologyNotesApril24th - Pain Readings Chapter 7...

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Unformatted text preview: Pain Readings: Chapter 7 Lecture 23 1 Plan Epidemiology Definitions Pain pathways Pain measurement Recap 2 Lecture 23 Epidemiology • Virtually everyone gets headaches – Severe & disabling for over 29 million in U.S.A. – $4 billion/year spent for relief • About 80% in U.S.A. suffer from back pain • About 50% of those over 70 yrs old in U.S.A. have arthritis • 30 to 40% of all cancer cases have pain • Heart disease • Dental pain • Childbirth Lecture 23 3 Definition of Pain • Unpleasant sensory experience Unpleasant associated with actual or potential tissue damage, or described in terms of such damage terms Lecture 23 4 Types of Pain • Acute pain – e.g., stubbed toe – Adaptive • Pre-chronic pain – Transition between acute and chronic pain – Helplessness predicts progress to chronic pain Helplessness • Chronic pain – Chronic recurrent pain – Debilitating, demoralizing Lecture 23 5 Features of Pain • Quality: Sharp, dull, burning, aching, etc. • Origin: Organic vs. inorganic (not psychogenic) • Time course: – Acute – Recurrent – Progressive • Experimental: e.g., electric shock Lecture 23 6 Pain Experience • Context-dependent – Combat vs. surgery – Torture vs. accident • Site-specific – Muscles, bones (deep tissue) vs. skin • Not directly related to extent of tissue Not damage damage • Suffering dependent on meaning ascribed Lecture 23 7 Pain Experience • Highly variable across individuals – Depends on learning history (e.g., conditioning, Depends secondary gain) secondary • Associated with anxiety, depression, Associated personality disorders personality • African-American people rate pain as more African-American intense and unpleasant than do Europeanintense American people • Women may report pain more readily than do Women men and have more pain-related disabilities men Lecture 23 8 Cross-Cultural Factors in Pain/Expression Culture Expectations Meaning • Childbirth for many Mexican women – “Dolor” – Childbirth is feared, severe pain is expected Pain Experience • Labor is painful, complications are common • Childbirth in Yap (South Pacific) culture – Childbirth is routine Lecture 23 – Women return to work immediately 9 Somatosensaory System • Primary afferents – Sensory receptors convert physical energy Sensory into neural impulses into – When sufficiently stimulated, neurons When discharge action potential • Chemical and electrical process – Afferent neurons carry signals from sense Afferent organs to central nervous system Lecture 23 10 Nociception • Nociceptors in skin, organs detect stimuli: – Heat – Cold – Crushing – Cutting – Burning • Fast, myelinated A fibers and slower C Fast, fibers convey sensory information – A-Delta fibers detect sharp, pricking pain – A-beta fibers fire easily – C fibers detect dull, aching pains Lecture 23 11 Spinal Cord • Afferent neurons group into nerves • Enter dorsal (back) side of spinal cord • Secondary afferents (transmission cells) Secondary carry messages to brain carry • Different neurons project to different layers Different (laminae) of the spinal cord (laminae) – Substantia gelatinosa receives A-delta and C Substantia fibers fibers – Modulates transmission of sensory info Lecture 23 12 Brain • Thalamus receives afferent input • Projects to somatosensory cortex • Areas with more receptors are better Areas represented in cortex represented – e.g., hands versus spleen • Cerebellum involved in pain • Anterior cingulate cortex active in both Anterior physical and emotional pain physical Lecture 23 13 Lecture 23 15 Brain Modulation of Pain • Periaqueductal gray area activity Periaqueductal relieves pain relieves • Projects to reticular formation and Projects medulla medulla • These project to spinal cord and These modulate transmission of pain signals modulate Lecture 23 16 Lecture 23 17 Neurotransmitters • Neurotransmitters are chemicals that allow Neurotransmitters neurons to communicate with one another neurons • Special receptors in the brain produce Special analgesia when occupied by endogenous or exogenous analgesics – Endorphins – Enkaphalins – Dynorphin – Can be triggered by pain, stress, suggestion Lecture 23 18 Pain-Enhancing Chemicals • Other chemicals increase pain – Act on spinal cord • Glutamate • Substance P – Released by tissue damage • Bradykinin • Protaglandins – Cytokines also increase pain sensitivity Cytokines (esp. in spinal cord) (esp. Lecture 23 19 Early Theories of Pain • Specificity theory: Separate pain system – Pain equal to tissue damage – Predicted specific receptors for each type of pain (heat, cold, etc.) – Predicted pain center in brain • Pattern theory: Pain reflects high levels of stimulation through other senses – Not as specific, but still focused on sensation Lecture 23 20 Critiques of Early Theories • Both are physiologically incorrect • Both fail to account for psychosocial factors that influence pain experience – Stress – Culture – Personality Lecture 23 21 Gate Control theory • Neural “gate” modulates pain signals before they reach brain • Gate is in spinal cord • Control of the gate: – Opened by activity in A-delta & C fibers – Closed by activity in A-beta fibers and other afferent fibers (e.g., rubbing, pressing) – Opened or closed by brain signals, a pathway for psychosocial influences Lecture 23 22 What opens the gate? • Physical conditions – Extent of injury – Physical activity • Emotional state – Anxiety – Tension – Depression • Cognitive processes – Focusing on the pain – Boredom Lecture 23 23 What closes the gate? • Physical Conditions – Medication – Counter-stimulation (rubbing, pressure) • Emotional State – Positive emotions – Rest, relaxation • Cognitive processes – Distraction Lecture 23 24 Neuromatrix • Melzack extended gate control theory • Neuromatrix emphasizes role of brain in Neuromatrix pain perception pain • Patterns of brain activity generate sense Patterns of whole body of – Normally processes incoming information – Can generate pain in absence of incoming Can information (e.g., phantom limb) information Lecture 23 25 Pain Measurement • Ask providers? – Very poor accuracy • Ask patients? – How create a reliable measure that How can be used clinically? can – Single item or scale? – Standardized tests that are hard to Standardized fake? fake? – Language and cultural equivalency? Lecture 23 26 Pain Measurement • Assess behavior? – e.g., limp, grimace, use of medication – Who does it? Takes a lot of training – Good for people who cannot provide selfreport • Measure physiology? – EMG to detect tension, spasms – Autonomic indicators (e.g., finger pulse) – Not well related to self-reported pain Lecture 23 27 Pain Scale Variations Visual Analog Scale No Pain Worst Pain Possible Worst Pain Possible Box Scale No Pain 0 1 2 3 4 5 6 7 8 9 10 Verbal Rating Scale No pain Some Pain Considerable Pain Worst Pain possible Wong-Baker Faces Pain Rating Scale Lecture 23 28 Multidimensional Assessment • McGill Pain Questionnaire – Assesses multiple dimensions of pain • • • • • • • Lecture 23 Sensory Affective Evaluative Indicate pain locale on drawings of body Circle descriptors that best describe pain Assesses temporal course of pain Intensity of present pain on 5-point scale 29 – Four sections West Haven-Yale Multidimensional West Pain Inventory Pain • Three sections – Pain experience • Characteristics of pain • Interference with life • Mood – Social effects • Ratings of others’ responses to patient’s pain – Daily activities • How often engage in common activities Lecture 23 30 Recap • Pain is pervasive and can have a major Pain effect on people’s lives effect • Pain is not simply sensation of tissue Pain damage damage • Actively regulated by brain • Influenced by experience • Expression subject to cultural influence • Difficult to assess Lecture 23 31 ...
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