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درد و قشر های حسی و حرکتی

1. درد و قشر های حسی و حرکتی. Types of Pain. Fast Pain Slow Pain. 3. Pain Perception. Fast pain : sharp and well localized, transmitted by myelinated axons Slow pain : dull aching sensation, not well localized, transmitted by unmyelinated axons

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درد و قشر های حسی و حرکتی

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  1. 1

  2. دردو قشر های حسی و حرکتی

  3. Types of Pain Fast Pain Slow Pain 3

  4. Pain Perception Fast pain: sharp and well localized, transmitted by myelinated axons Slow pain: dull aching sensation, not well localized, transmitted by unmyelinated axons Visceral pain: not as well localized as pain originating from the skin  pain impulses travel on secondary axons dedicated to the somatic afferents  referred pain 4

  5. Fast Pain Pathway Ventrobasal Nucleus I Lamina Marginalis II IV III VI V VII Anterolateral Pathway Substantia Gelatinosa IX VIII

  6. Slow Pain Pathway Ventrobasal Nucleus Lamina Marginalis I II IV III VI V VII Substantia Gelatinosa Anterolateral Pathway IX VIII

  7. Types of Neurons Afferent (Ascending) – transmit impulses from the periphery to the brain First Order neuron Second Order neuron Third Order neuron Efferent (Descending) – transmit impulses from the brain to the periphery 7

  8. Pain and Temperature(Anterolateral System ) Cerebral Cortex 3 Thalmus 2 1 Spinal cord 8

  9. Nociceptors = specialized terminal peripheral branches of sensory nerve fibers that are sensitive to noxious stimuli

  10. Pain Mediators Result from tissue damage, inflammation or ischemic changes in the tissues provoking the chemical stimulation of nerves. 10

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  13. Theories of Pain 1) Specificity Theory 2) Pattern Theory 3) Gate Control Theory

  14. Theories/ The Specificity Theory • - pain is a sensation, like vision or hearing, conveyed via unique anatomical structures • Evidence for specificity theory: existence of nociceptors

  15. Theories/ The Pattern Theory • Pain results from a pattern of intense activity of neurons that also can encode subtle sensations such as warmth or fine touch

  16. Gate Control Theory Melzack & Wall, 1982 Substantia Gelatinosa (SG) in dorsal horn of spinal cord acts as a ‘gate’ – only allows one type of impulses to connect with the SON Transmission Cell (T-cell) – distal end of the SON If A-beta neurons are stimulated – SG is activated which closes the gate to A-delta & C neurons If A-delta & C neurons are stimulated – SG is blocked which closes the gate to A-beta neurons 21

  17. Gate Control Theory • Spinal cord areas that receive messages from pain receptors, also receive input from other skin receptors and from axons descending from the brain • these other inputs sometimes close the “gates” for the pain mesages.

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  19. Gate Control Theory Melzack & Wall (1982) 24

  20. Gate Control Model (1) 25

  21. Gate Control Theory (1) 26

  22. PAIN INHIBITORY COMPLEX: Presynaptic Inhibition BRAIN STEM.NEURON ANTEROLATERAL PATHWAY INHIBITORY NEURON - PAIN RECEPTOR + DORSAL HORN OF SPINAL CORD

  23. PAIN INHIBITORY COMPLEX: Postsynaptic Inhibition BRAIN STEM.NEURON ANTEROLATERAL PATHWAY INHIBITORY NEURON - PAIN RECEPTOR + DORSAL HORN OF SPINAL CORD

  24. Gate Control Theory (1,2) 29

  25. Gate control Model (2)

  26. Other Considerations • Drugs can suppress pain sensitivity or block pathway • Analgesia : No sensation • Hypalgesia (Analgesia) : Decreased pain (higher threshold) • Hyperalgesia: Increased pain (lower threshold) • Referred pain: one site has pain but felt in another site

  27. The Analgesia System 1) Periaquaductal Gray 2a) Lateral Tegmental Nucleus 2b) Locus Ceruleus 2c) Raphe Magnus Nucleus 3) Pain inhibitory complex in dorsal horns (Substantia Gelatinosa) 32

  28. Stress Induced Analgesia 33

  29. Hyperalgesia Primary Hyperalgesia – due to injury (sensory receptor level) Secondary Hyperalgesia – due to spreading of chemical mediators (CNS level-injury of Spinal Cord & Thalamus) 34

  30. Referred Pain Dermatomal Theory Convergence Theory Facilitation Theory 35

  31. Referred PAIN(Convergence Theory-1) • Visceral pain fibers synapse on same secondary neurons as receive pain fibers from skin

  32. Referred pain (ConvergenceTheory-2) 37

  33. Acupuncture 38

  34. Cerebral Cortex • Three kinds of functional areas: • Sensory areas– conscious awareness of sensation • Motor areas– control voluntary movement • Association areas– integrate diverse information, communicate “associate” with the motor cortex and sensory association areas to analyze input

  35. ناحیه حسی پیکری 1 • منطبق با نواحی 1 و2 و 3 برودمن • در خلف شیار مرکزی و در شکنج پس مرکزی • موقعیت قسمتهای مختلف بدن در این ناحیه بسیاردقیق است

  36. Sensory Homunculus

  37. Areas input 3b&1:information from receptors in the skin 3a&2:proprioceptive information from receptors in muscles and joints This information from the skin is further processed within area 1 and then combined with information from muscles and joints in area 2 A small discrete lesion in area 1 impairs tactile discrimination Whereas a small lesion in area 2 impairs the ability to recognize the size and shape of a grasped object.

  38. Inputs & outputs The cells in areas 3a and 3b project their axons to areas 1 and 2 Most thalamic fibers terminate in areas 3a and 3b Thalamic neurons send a small projection directly to Brodmann’s areas 1,2

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