N109: Foundations in Nursing Practice

N109: Foundations in Nursing Practice Study Guide must be recognized that the experience of pain is subjective and the expression of pain may be influenced by the patient’s culture. 2.3 Physiology of Pain The process of nociception describes the normal processing of pain and the responses to noxious stimuli that are damaging or potentially damaging to normal tissue. There are four basic processes involved in nociception. These are: • Transduction: Pain perception begins when the nerve endings respond to a noxious stimulus. The stimulus can be mechanical (pressure, swelling, incision, abscess, etc.), thermal (burn), or chemical (toxin or infection). • Transmission: Transmission occurs from the site of transduction, through the spinal cord, into the brain stem, and then into the higher levels of the brain. • Perception: The end result of the neuronal activity is the actual perception of pain when pain becomes a conscious experience. • Modulation: Special pathways in the spinal cord can lead to an increase in the transmission of pain impulses (excitation) or a decrease in transmission (inhibition). Some of the neurotransmitters that tend to inhibit transmission of pain impulses include endorphins, enkephalins, serotonin, norepinephrine, acetylcholine, and oxytocin. Gate Control Theory of Pain To explain how thoughts and emotions influence pain perception, Ronald Melzack and Patrick Wall proposed that a gating mechanism exists within the dorsal horn of the spinal cord. The peripheral nervous system interacts with the spinal cord and the brain. The interplay among these connections determines whether or not painful stimuli go to the brain. In the gate control theory, before they can reach the brain, these painmessages encounter “gates” in the spinal cord that open or close depending upon a number of factors. When the gates are open, pain messages “get through” more or less easily and pain can be intense. When the gates close, pain messages are prevented from reaching the brain and the patient may not experience the sensation of pain. Pain Threshold vs. Pain Tolerance The individual’s pain threshold is the point at which a stimulus, usually one associated with pressure or temperature, activates pain receptors and produces a sensation of pain. The individual’s pain tolerance is themaximum level of pain that an individual can tolerate at any particular point in time. While thepain threshold is relatively consistent across time, the individual’s pain tolerance may vary widely. Psychology of Pain In 1968, Ronald Melzack and Kenneth Casey described pain in terms of three dimensions: • Sensory-discriminative: Sense of the intensity, location, quality, and duration of the pain • Affective-motivational: Unpleasantness and the urge to escape the unpleasantness • Cognitive-evaluative: Cognitions such as appraisal, cultural values, distraction, and hypnotic suggestion

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