no 28 - 辽宁医学院

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1、No.281.MotorPathwaysⅡ.TheMotor(descending)PathwaysThemotorpathwaysareconcernedwithmotorfunction,andcomposedofuppermotorneuronsandlowermotorneurons.Theuppermotorneuronsaretheefferentneuronsfromthecerebralcortextothemotornucleiofcranialnervesandanteriorhornsofspinalcord.Thelo

2、wermotorneuronsarethenervesinthemotornucleiofcranialnervesandtheanteriorhornsofspinalcord.Thecellbodiesandaxonsoflowermotorneuronsserveasthefinalcommonpathwayconnectingmotorimpulses.Themotorpathwaysincludepyramidalandextrapyramidalsystems.Ⅰ)ThePyramidalSystemItisconcernedwi

3、ththevoluntarymovementoftheskeletalmusclesandiscomposedoftwoordersofneurons,i.e.theupperandlowermotorneurons.Theuppermotorneuronsarecomposedofthegiantpyramidalcells(Betzcells)andotherpyramidalcellsofvarioussizedwhicharelocatedintheprecentralgyrusandtheanteriorpartofparacent

4、rallobuleandthepyramidalcellsinthesomeareasoffrontal,parietallobes.Theiraxonsformthedescendingpyramidaltract,amongwhich,thefibersendinginthecranialmotornucleiaredesignatedasthecorticonucleartractandthoseterminatingintheanteriorhornofthespinalcordascorticospinaltract.Thelowe

5、rmotorneuronsincludethecranialmotorcellsofthebrainstemandspinalmotorcellsofthespinalcord.1.ThecorticospinaltractTheuppermotorneuronsarethepyramidalpyramidalcellsinthesuperiorandmiddlepartsoftheprecentralgyrusandtheanteriorpartofparacentrallobule.Theaxonsarisingfromtheseuppe

6、rmotorneuronsformthecorticospinaltract.Ittraversestheposteriorlimbofinternalcapsule,theintermediate3/5ofthecruscerebri,thebasilarpartofthepons,andtheventralpartofthemedullaoblongata.Inthecaudalpartofthemedullaoblongatathegreaterpart(75-90%)ofthetractcrossestotheoppositeside

7、toformthepyramidaldecussationandcontinuesasthelateralcorticospinaltractinthelateralfuniculusofthespinalcord.Thefibersofthelateralcorticospinaltractterminateintheanteriorgrayhornsofallthespinalsegmentscontrollingthemovementsofmusclesofthelimbs.Thenon-crossedfiberscontinueast

8、heanteriorcorticospinaltractdirectlyintotheanteriorfuniculusofthesamesideandcrosst