1. بسم الله الرحمن الرحيم

5. If persistent, physiological pain may progress to a pathological condition itself, often referred to as maladaptive pain, in which case pain is dissociated from the original noxious stimulation or the healing process and thus does not represent anymore a symptom of disease but rather abnormal sensory processing due to damage to tissues (inflammatory pain) or the nervous system (neuropathic pain), or to abnormal function of the nervous system itself (functional pain) . pain resulting from activation of pain receptors may be referred to as adaptive or physiological pain, because it minimizes tissue damage and promotes healing.

17. Visceral Somatic sympathetically innervated organs can be transferred to body surface cutaneous, deep tissues site vague distribution and Quality deep, ache, dragging, squeezing acute: colic, paroxysmal, +/- N/V, sweating, BP and heart rate changes constant, localised aching, throbbing, gnawing character Acute nociceptive pain:

18. Slow (delayed) pathophysiological pain Fast (Immediate) physiological pain Shortly after application if tissue damage occurs Longer duration Burning Poorly-localized C-fibers Thalamus Substance-P * Associated with arousal, autonomic & emotional reactions Abolished by local anaethesia & morphine onset: during application of the stimulus Duration: short duration. Nature: pricking Localization: well-localized Afferent: A-delta fibers Higher center: CC Neurotransmitter: glutamate Significance: * determine site & severity. * Initiate withdrawal reflexes. Abolished by deep pressure and not abolished by morphine.

19. Reactions to Pain: 1) Somatic Motor Reactions 2) Autonomic Reactions 3) Emotional and Psychogenic Reactions 4) Hyperalgesia.

20. 1) Somatic Motor Reactions a) Excess neuromuscular excitability throughout the body. b) Withdrawal Reflexes. - initiated by cutaneous pain . - Aim to withdraw the whole body or a part of it away from a painful stimulus mainly by contraction of flexor muscles. - It is a prepotent reflex; inhibit all other reflexes during its occurrence. Reflex spasm of the nearby skeletal muscles in case of deep pain ----> minimize mobilization of the pained part ----->  stimulation of pain receptors. c) Immobilization Reaction. d) Guarding Reaction. Reflex spasm of the overlying skeletal muscles in case of visceral pain ---->  stimulation of pain receptors in the diseased viscus.

36. Relief of pain (analgesia) This may be done by: 1- Physiological method (edogenous analgesic system). 2- Pharmacological. 3- Surgical by many methods as cutting of the peripheral nerves. Prefrontal lobectomy may be used in sever cases. It abolishes only the emotional and psychogenic effect of pain but associated with sever personality changes. So, this method is used in terminal stages of severly painful conditions as tumour.

38. Location 1-The periaqueductal gray area (PAG area) around the aqueduct of sylvius in the midbrain and pons. 2-The raphe magnus (NRM) nucleus located in the lower region of the pons and upper region of the medulla. 3-The nucleus reticularis paragiganto -cellularis in the medulla. 4- Locus ceruleus (NC) in pons 5- A pain inhibitory complex located in the dorsal horn of the spinal cord (probably in laminae II and III : the substantia gelatinosa of Rolandi).

40. Activation of the Pain Control System Clinical (Experimental) Natural (physiological) 1- Electrical stimulation of certain regions of pain control system 2- Local application of opiates (such as morphine) at particular regions in the nervous system. (pharmacological anesthesia) Exposure to severe stress , particularly when associated with strong emotional excitement .

41. PAG Midbrain C.C. Periventricular area of the hypothalamus Limbic system Reticular formation Ascending pain pathway + + + + + Enkephalin --- GABA --- ++ LC NRM GABA --- ++ Enkephalin --- Serotonin +++ Epinephrine +++ Pons Spinal Cord 1 st order neuron in the pain pathway 2nd order neuron in the pain pathway Enkephalin --- How stress activates the pain control system?

43. Enkephalin binds to opiate receptors in: 1- Central terminal of 1st order neuron -----> opening of Cl channel -----> Cl influx -----> hyperpolarization -----> block of Ca influx -----> inhibit release of chemical transmitter from 1st order neuron 2- postsynaptic 2nd order neuron in pain pathway ------> opening of K channels -----> hyperpolarization -----> inhibit their response to the pain chemical transmitter.

46. Impulses from tactile receptors +

47. 3- Acupuncture Acupuncture has been practiced in China for more than 4000 years as a method for pain relief. Mechanism: 1- needles in appropriate body regions are thought to excite certain sensory neural pathways which feed into the brain stem centers (such as the PAG) involved in the pain control system, with release of endogenous opioid peptides. 2- simultaneous suppression of pain transmission at the spinal pain-gate by acupuncture

48. Thank You