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27 terms

Ch. 13 - Pain

Pain anatomy, theories, and neuromodulation
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sensory/discriminative system
processes info about strength, intensity, and time/space aspects of pain, results in prompt withdrawal from painful stimulus; mediated by afferent nerve fibers, spinal cord, brain stem, and higher brain centers
motivational/affective system
determines individual's conditioned or learned approach/avoidance behaviors; mediated by interaction of reticular formation, limbic system, adn brain stem
cognitive/evaluative system
overlies individual's learned behavior concerning experience of pain; may block, modulate, or enhance perception of pain
3 systems that interact to produce pain
sensory/discriminative, motivational/affective , cognitive/evaluative
nociceptors
free nerve endings that respond to chemical, mechanical, and thermal stimuli
nociception
perception of pain
portions of nervous system responsible for sensation and perception of pain
afferent pathways, interpretive centers, efferent pathways
location afferent pathways
PNS, travel to spinal gate in dorsal horn, then ascend to higher centers in CNS
location interpretive centers
brainstem, midbrain, diencephalon, cerebral cortex
efferent pathways
descend from CNS back to dorsal horn of the spinal cord
A(delta) fibers
type of nociceptor, lightly myelinated afferent neurons, carry sharp, well-localized pain sensations, rapid transmission
C fibers
type of nociceptor, small unmyelinated , transmit burning or aching sensations, slow transmission
lateral neospinothalamic tract
carries acute pain info to lateral thalamus, then projets to somatosensory cortex which provides specific pain info
medial paleospinothalamic tract
carries dull and burning pain info to midbrain, is responsible for reflex responses to pain with changes in autonomic function, respiration, circulation, and endocrine function
ventromedial medulla
afferent stimulation of this portion of midbrain stimulates efferent pathways, which modulate or inhibit afferent pain signals at the dorsal horn
periaqueductal gray (PAG)
gray matter surrounding the cerebral aqueduct
periaqueductal gray (PAG)
afferent stimulation of this portion of midbrain stimulates efferent pathways, which modulate or inhibit afferent pain signals at the dorsal horn
specificity theory
pain intensity proportinoal to amount of tissue injury
gate control theory
stimulationof non-nociceptive A fibers (touch, vibration, thermal) causes cells in substantia gelatinosa to close itself off from pain impulses, which diminishes pain sensation
substantia gelatinosa
laminae in the dorsal horn of spinal cord; A and C fibers terminate here
neuromatrix theory of pain
when there is no discernable cause for chronic pain, the brain produces pattern of nerve impulses from widely distributed neural network; impulses can originate independently in brain w/o external input
endorphins
family of neuropeptides that inhibit transmissino of pain impuses in spinal cord and brain
endorphins bind to
mu, kappa, or delta opioid receptors--opiate receptors on the plasma membrane of the afferent neuron; inhibits release of excitatory neurotransmitters
Beta-endorphin
potent endorphin released from hypohalamus and pituitary gland; may result in general sensations of well-being
enkephalin
endorphin found in neurons of brain and spinal cord, weaker analgesic than other endorphins, more potent and longer lasting than morphine
dynorphin
endorphin found in hypothalamus, periaqueductal gray, and spinal dorsal horn; generally impedes pain signals but can incite pain
endomorphins
peptides formed in the brain, highly antinoceceptive, high affinity for morphine receptors. Cause vasodilation by releas of NO from endothelial cells