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Submitted by psychchick9979 on 06/30/2008 05:21 PM
- Category: English
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Endogenous Opioids: The Body's Natural Painkillers
Introduction. Pain is one of the body's most important adaptive mechanisms, with its primary function being protection. The brain is quickly notified that tissue damage is occurring or that it is about to occur so that behavioral responses may intervene to avoid or minimize that damage. If tissue damage has occurred, pain plays a part in hindering activity in order to make the environment more conducive to healing. In a "fight or flight" survival situation, however, pain would have negative effects. Therefore, the body produces substances, endogenous opioids, that have analgesic properties to make us better able to tolerate pain. These substances -- endorphins, enkephalins, and dynorphins -- also have behavioral effects and neurotransmitter and neuromodulator functions (1). Endorphins were named by combining the words endogenous and morphine (2) and their discovery occurred when a substance exhibiting the analgesic characteristics of morphine was extracted from the brain. This discovery was confirmed when the action of the substance was blocked by the morphine antagonist naloxone (3).
The pain response begins with an undesirable stimulus activating one or more types of peripheral pain receptors known as mechanical, thermal, and polymodal nociceptors (4). Information about the stimulus travels along these afferent nerves to the spinal cord, where the neurotransmitter substance P is released. Without the transmission of substance P, no pain perception information can travel to the brain to be processed. Substance P binds to spinal nerve receptors to allow the noxious information to travel to sites where it can be processed, including the brain stem, thalamus, limbic system, and somatosensory cortex.
Two descending pathways from the brain regulate pain. A pathway stretching from the locus caeruleus of the medulla to the dorsal horn acts as an analgesic by releasing norepinepherine,...
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