| Analgesia is a state in which a person has reduced sensitivity to painful
stimuli. Drugs that induce analgesia are commonly known as pain relievers.
Opioids bring about analgesia by interfering with the pain perception pathway
in the nervous system (Leonard, 1992).
Pain impulses initiate from an area of trauma, usually near the surface of the body. The impulses travel through sensory neurons to the substantia gelatinosa, a narrow zone of neurons in the brain stem where preliminary interpretation of the information takes place. From here, signals for sharp, localized pain travel to the lemniscus |
system for interpretation. Signals for dull, burning pain travel
to the medial thalamus (Snyder, 1996).
Like other impulses in the nervous system, pain signals depend on the
release of neurotransmitters from one neuron and the reception of these
neurotransmitters by another neuron. Substance P is the main neurotransmitter
that carries pain signals across synapses, the space between neurons.
Electrical impulses that travel through neurons signal for the release
of neurotransmitters into the synapse (Kandel and Schwartz, 1985).
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| Signals for slow, dull pain travel through paleospinothamlamic pathway within in the brain, while fast, sharp pain signals travel through the neospinothalamic system. Image from Snyder, 1996. Used with permission by W.H. Freeman and Company. |
| Continue: Analgesia (part 2) |
Animal Physiology HOT TOPICS |
This site was created during the fall semester of 1999 by Wes
Self, a student at
Davidson College, as part of an assignment in Biology 312 (Animal Physiology). Questions, comments and suggestions are appreciated at weself@davidson.edu |