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Posterior column–medial lemniscus pathway (PCML) (also known as the dorsal column-medial lemniscus pathway) is a sensory pathway of the central nervous system that conveys localized sensations of fine touch, vibration, two-point discrimination, and proprioception (position sense) from the skin and joints. It transmits information from the body to the postcentral gyrus of the cerebral cortex.〔O'Sullivan, S. B., & Schmitz, T. J. (2007). Physical Rehabilitation (5th Edition ed.). Philadelphia: F.A. Davis Company.〕 There are three neurons involved in the pathway: first-order neurons, second-order neurons, and third-order neurons. The first-order neurons reside in dorsal root ganglia and send their axons through the gracile fasciculus and cuneate fasciculus.〔Giuffrida R and Rustioni A. Dorsal root ganglion neurons projecting to the dorsal column nuclei of rats. J Comp Neurol. 1992 Feb 8;316(2):206-20. http://www.ncbi.nlm.nih.gov/pubmed/1374085〕 The first-order axons make contact with second order neurons at the gracile and cuneate nuclei in the lower medulla. The second-order neurons send their axons to the thalamus. The third order neurons arise from thalamus to the postcentral gyrus. The posterior column is composed of gracile fasciculus and cuneate fasciculus. The gracile fasciculus carries input from the lower half of the body and the cuneate fasciculus carries input from the upper half of the body. The gracile fasciculus arise from the fibers more medial than the cuneate fasciculus. When the axons of second-order neurons of the dorsal column system decussate in the medulla, they are called internal arcuate fibers. The crossings of the internal arcuate fibers form the medial lemniscus. The name comes from the two structures that the sensation travels up: the posterior (or dorsal) column of the spinal cord, and the medial lemniscus in the brainstem. The PCML pathway is composed of rapidly conducting, large, myelinated fibers.〔 ==Structure== Discriminative sensation is well developed in the fingers of humans, and allows us to feel fine textures and determine what an unknown object in our hands is without looking at it (stereognosis). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Posterior column–medial lemniscus pathway」の詳細全文を読む スポンサード リンク
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