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中枢神经解剖.pdf

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Chapter14 BrainandCranialNerves TheBrain Rostral(towardthe nose) Caudal(towardthetail) Majordivisionsofthe brain: 1.cerebrum 2.diencephalon 3.cerebellum 4.brainstem cerebrumis83%of brainvolume cerebellumcontains 50%oftheneurons brainweighs3to3.5 pounds BLOODSUPPLYTOTHEBRAIN Althoughthebrainisonly2%ofthebody'sweightit receives15%-20%ofthebloodpumpedbytheheart. Disruptionofthebloodsupplyforafewsecondscan causeunconsciousness,andforafewminutes irreversibledamage. Theblood-brainbarrierisformedbytheepithelialcellsof capillariesinthebrain. Thecellsarejoinedtogetherbytightjunctions,which preventsubstancesfrompassingbetweenthecells. Astrocytesinfluencetheformationofthebloodbrain barrier. DivisionsoftheBrain Brainstem BrainStem:MedullaOblongata Ascendinganddescending nervetractsMotorfibers decussateinmedullary pyramids Cardiaccenteradjustsrate andforceofheartbeat Vasomotorcenteradjusts bloodvesseldiameter Respiratorycenterscontrol rateanddepthofbreathing Reflexcentersfor coughing,sneezing, gagging,swallowing, vomiting,salivation, sweating,movementsof tongue&head BrainStem:Pons Bulgeinthebrainstem Ascendingsensorytracts DescendingmotortractsPons Pathwaysinandoutof cerebellum Nucleiconcernedwith sleep,hearing,balance, taste,eyemovements, facialexpression,facial sensation,respiration, swallowing,bladder controlandposturePons BrainStem:Midbrain Thecerebralpeduncles containdescendingmotor nervetracts Thecorporaquadrigeminais Midbrain fourmoundsontheposteriorCerebral midbrain,dividedintothepeduncles Corpora superiorandinferiorcolliculi.quadrigemina Thesuperiorcolliculi involvedwithvisual reflexes Theinferiorcolliculiare involvedwithhearingand auditoryreflexes. Dysfunctionofthe substantianigra,anucleus inthemidbrain,resultsin Parkinson'sdisease. BrainStem:ReticularFormation acollectionofnucleiandnervetractsthatformthecore ofthebrainstem. Integrationofcranialnervereflexes.Thatis,the reticularformationnucleiconnecttoandinteractwith thecranialnervenuclei. Auton