Anterior spinothalamic tract concerned with crude

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Anterior spinothalamic tract ● concerned with crude touch, the sensation produced by stroking glabrous skin with a wisp of cotton. ● receives input from free nerve endings and from Merkel tactile disks. a. First-order neurons ● found in spinal ganglia at all levels. ● project axons into the medial root entry zone to second-order neurons in the posterior horn. b. Second-order neurons ● located in the posterior horn. ● give rise to axons that decussate in the anterior white commissure and ascend in the contralateral anterior funiculus. ● terminate in the VPL nucleus of the thalamus. c. Third-order neurons ● found in the VPL nucleus of the thalamus. ● project via the posterior limb of the internal capsule and corona radiata to the postcentral gyrus (areas 3, 1, and 2). Lateral spinothalamic tract ● mediates itch, pain, and temperature sensation. ● receives input from free nerve endings and thermal receptors. ● receives input from A-δ and C fibers (i.e., fast- and slow-conducting pain fibers). ● somatotopically organized with sacral fibers posterolaterally and cervical fibers anterolaterally. a. First-order neurons ● found in spinal ganglia at all levels. ● project axons via the posterolateral tract (of Lissauer) to second-order neurons in the posterior horn. ● synapse with second-order neurons in the posterior horn. b. Second-order neurons ● found in the posterior horn. ● give rise to axons that decussate in the anterior white commissure and ascend in the anterior half of the lateral funiculus. ● project collaterals to the reticular formation. ● terminate contralaterally in the VPL nucleus and bilaterally in the intralaminar nuclei of the thalamus. c. Third-order neurons ● found in the VPL nucleus and in the intralaminar nuclei. (1) VPL neurons ● project via the posterior limb of the internal capsule to the somatesthetic cortex of the postcentral gyrus (areas 3, 1, and 2). (2) Intralaminar neurons ● project to the caudatoputamen and to the frontal and parietal cortex. Posterior column–medial lemniscus pathway
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● mediates fine touch, conscious proprioception, and vibratory sense. ● somato-topically organized. ● receives input from Pacinian and Meissner’s corpuscles, joint receptors, muscle spindles, and Golgi tendon organs (GTOs). 1. First-order neurons ● located in spinal ganglia at all levels. ● give rise to the fasciculus gracilis from the lower extremity. ● give rise to the fasciculus cuneatus from the upper extremity. ● give rise to axons that ascend in the posterior columns and terminate in the gracile and cuneate nuclei of the medulla. 2. Second-order neurons ● located in the gracile and cuneate nuclei of the caudal medulla. ● give rise to axons, internal arcuate fibers that decussate and form a compact fiber bundle, the medial lemniscus. The medial lemniscus ascends through the contralateral brainstem to terminate in the ventral posterolateral (VPL) nucleus of the thalamus.
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  • Winter '18
  • Jane doe

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