10Pain-1 - Pain Receptors Pain receptors are called...

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Pain
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Receptors Pain receptors are called nociceptors Nociceptors are usually free nerve endings Nociception constitutes an anatomically distinct modality from discriminative perception and thermoception.
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Nociceptors cont’d Nerve cell bodies reside in DRG
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Dorsal horn
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Classification of Nociceptors Based on conduction velocity of AP’s A δ fibers - conduct at about 20 m/s C fibers - conduct at about 2 m/s (contrast w/A β fibers at 35-75 m/s) Based on conduction velocity and modality A δ mechanosensitive A δ mechanothermal - assoc’d w/sharp, first pain C polymodal - assoc’d w/dull, slow pain
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Major Central Pain Pathways Spinothalamic tract Pain fibers associated with discriminative aspect of pain (location, intensity and quality) from body Enter via dorsal tract of Lissauer Ascend a couple of spinal segments Penetrate gray matter and synapse w/targets in several of Rexed’s laminae
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2nd order neurons Decussation
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Spinothalamic Tract cont’d Axons ascend via anterolateral tract and (continuing into the brain) via the spinothalamic tract to the thalamus Synapse on 3rd order neurons in thalamus, which project to post-central gyrus
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Trigeminal Tract
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1st order neurons 2nd order neurons 3rd order neurons
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Significance Evolutionary - who knows? Clinical - Dissociated sensory loss
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CTMC
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Affective, Motivational Pathway The parts of the pain system that convey unpleasantness of pain fear and anxiety associated with pain
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10Pain-1 - Pain Receptors Pain receptors are called...

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