Pain

Pain
?An unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage"
International Association for the Study of Pain
Pain Sensation
?Protective mechanism.
?Damage to body tissues.
?Removal from the pain stimulus
?Pain Receptors: Free nerve endings.
?Superficial layers of the skin, periosteum, the arterial walls, joint surfaces, falx cerebri, and tentorium of the cranial valut.
Stimuli that can excite Pain Receptors
?Mechanical, thermal, and chemical
?Chemicals include:
?Bradykinin, Serotonin & Histamine
?K ions & Acids
?Acetylcholine
?Proteolytic enzymes
?In addition, PGs and substance P also enhances the sensitivity of pain endings but do not directly excite them.
Non-adapting Nature of the Pain Receptors
?Adapt very little and some times not all.
?Continued stimulation ?greater excitation of pain fibers becomes ? Hyperalgesia
?Little adaptation ? person apprised of a damaging stimulus.
Tissue Ischemia & Pain
?Blocking blood flow ? pain within few minutes.
?Why? The greater the rate of metabolism of the tissue the more rapidly the pain appears.
?Caused by:
A.Ischemia ? large amounts of lactic acids.
B.Chemical agents (bradykinin and proteolytic enzymes after the cell damage).