The most comprehensive information-delivery system, and one which has the most unpleasant effects on our consciousness, concerns our sense impressions of pain. We distinguish two types of pain sensations: epicritic, meaning that the pain is sharp, distinct and localised, and protopathic, meaning that it is dull, not precisely definable, diffuse and deep. Specific pain chemoreceptors react to a variety of substances: plasma kinins, bradykinin, histamine, serotonin, prostaglandins and neuroleptic drugs, while non-specific mechanisms may amplify our subjective impressions of pain. Our individual constitutions, together with the circumstantial effects of the different neurotransmitters, can significantly alter the way we actually feel pain: NA increases our perception of pain, and the NAassociated anxiety likewise contributes to our apprehension of pain. Heightening of consciousness (the“arousal reaction”) also increases sensitivity to pain. Ischemia raises the sensitivity of the pain receptors in the affected part. Thus there is considerable variability in the pain threshold. People with a sympathotonic constitution tend to feel pain more, while those of a“vagal” type appear to have their pain threshold set higher.
KeywordsHerpes Zoster Pain Threshold Trigeminal Neuralgia Pain Sensation Neck Muscle
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