limbic system meninges of the brain basal ganglia cn iimul.umlub.edu.pl/en/system/files/presentation...
TRANSCRIPT
Thelimbicsystemisresponsibleforcontrolofouremotionsandbehaviour,motivationandmemory,alsoaffectstheautonomicandsomaticnervoussystemaswellastheendocrinehypothalamus-hypophysealaxis.Thelimbicsystemisexpressedthroughthehypothalamusbywayoftheautonomicnervoussystem.
LIMBICSYSTEM
Aprominentstructureinthelimbicsystemisthehippocampalformationonthemedialaspectofthetemporallobe.Itconsistsofacoreofcorticalanddiencephalicstructuresfoundonthemedialaspectofthehemisphere.
Thehippocampalformationextendsalongtheflooroftheinferiorhornofthelateralventricleinthetemporallobeandincludesthehippocampus,thedentategyrus,thesubiculum,andadjacententorhinalcortex.Thehippocampusischaracterizedbya3-layeredcerebralcortex.
LIMBICSYSTEM
Otherlimbic-relatedstructuresincludetheamygdala,whichislocateddeepinthemedialpartoftheanteriortemporalloberostraltothehippocampus,andtheseptalnuclei,locatedmediallybetweentheanteriorhornsofthelateralventricle.
Thelimbicsystemisinterconnectedwiththalamicandhypothalamicstructures,includingtheanterioranddorsomedialnucleiofthethalamusandthemammillarybodiesofthehypothalamus.
LIMBICSYSTEM
Thecingulategyrusisthemainlimbiccorticalarea.Thecingulategyrusislocatedonthemedialsurfaceofeachhemisphereabovethecorpuscallosum.Limbic-relatedstructuresalsoprojecttowideareasoftheprefrontalcortex.
Thelimbicsystemisinvolvedinemotion,memory,attention,feeding,andmatingbehaviors.Thelimbicsystemmodulatesfeelings,suchasfear,anxiety,sadness,happiness,sexualpleasure,andfamiliarity.
LIMBICSYSTEM
Theterm‘limbicsystem’hasbecomepopulartodescribethelimbiclobealongwiththecloselyassociatedsubcorticalnuclei,includingtheamygdala,septum,hypothalamus,habenula,anteriorthalamicnucleiandpartsofthebasalganglia.
Thelimbicsystemconsistsof- corticaland- subcorticalstructures.Thecorticalstructuresarelocatedpredominantlyonthemedialaspectofthecerebralhemispheres.Thesubcorticalstructuresarelocatedinthebasalganglia,diencephaion,brainstem,andreticularformation.Thesestructuresarereciprocallyinterconnectedbyvariousneuralpathwaysandcircuits,andtheycontributetotheregulationofhomeostasis.
LIMBICSYSTEM
MAJORPARTSOFTHELIMBICSYSTEM:Theorbitofrontalcortexmediatestheconsciousperceptionofsmell.Ithasreciprocalconnectionswiththemediodorsalnucleusofthethalamus.Itisinterconnectedthroughthemedialforebrainbundlewiththeseptalareaandhypothalamicnuclei.Thedorsomedialmediodorsalnucleusofthethalamushasreciprocalconnectionswiththeorbitofrontalandprefrontalcorticesandthehypothalamus.Itreceivesinputfromtheamygdalaandplaysaroleinaffectivebehaviorandmemory.Theanteriornucleusofthethalamusreceivesinputfromthemamillarynucleusthroughthemamillothalamictractandfornix.ItprojectstothecingulategyrusandisamajorlinkinthePapezcircuit.
LIMBICSYSTEM
MAJORPARTSOFTHELIMBICSYSTEM:Theseptalareaisatelencephalicstructure.Ithasreciprocalconnectionswiththehippocampalformationthroughthefornixandwiththehypothalamusthroughthemedialforebrainbundle.Itprojectsthroughthestriamedullaris(thalami)tothehabenularnucleus.Thelimbiclobeincludesthesubcallosalarea,paraterminalgyrus,cingulategyrusandisthmus,andparahippocampalgyrus,whichincludestheuncus.Itcontains,buriedintheparahippocampalgyrus,thehippocampalformationandamygdaloidnuclearcomplex.
LIMBICSYSTEM
MAJORPARTSOFTHELIMBICSYSTEM:Thehippocampalformationisasheetofarchicortexthatisjelly-rolledintotheparahippocampalgyrus.Itfunctionsinlearning,memory,andrecognitionofnovelty.
LIMBICSYSTEM
Theamygdaloidcomplex(amygdala)isabasalnucleusthatunderliestheparahippocampaluncus.Inhumans,stimulationcausesfearandsignsofsympatheticoveractivity.Lesionscauseplacidityandhypersexualbehavior.Thehypothalamushasreciprocalconnectionswiththeamygdala.Thelimbicmidbrainnucleiandassociatedneurotransmittersincludetheventraltegmentalarea(dopamine),raphenuclei(serotonin),andlocusceruleus(norepinephrine).Thehippocampalformationreceivesmajorinputthroughtheentorhinalcortexandprojectsmajoroutputthroughthefornix.
Themajorstructuresofhippocampalformation:1.Thedentategyrus,whichhasathree-layeredarchicortex.Itcontainsgranulecellsthatreceivehippocampalinputandprojectoutputtothepyramidalcellsofthehippocampusandsubiculum.2.Thehippocampus(cornuAmmonis),whichhasathree-layeredarchicortex.Itcontainspyramidalcellsthatprojectthroughthefornixtotheseptalareaandhypothalamus.3.Thesubiculum,whichreceivesinputthroughthehippocampalpyramidalcells.Itprojectsthroughthefornixtothemamillarynucleiandtheanteriornucleusofthethalamus.
LIMBICSYSTEM
Theamygdaloidcomplex(amygdala)gets:1.Inputisfromthesensoryassociationcortices,olfactorybulbandcortex,hypothalamusandseptalarea,andhippocampalformation.2.Outputisthroughthestriaterminalistothehypothalamusandseptalarea.Thereisalsooutputtothedorsomedialnucleusofthethalamus.
LIMBICSYSTEM
Onthebasisofemotionaldisturbancesdisplayedbypatientswhopresentedwithdamagetothehippocampusandcingulategyrus,Papez(1937)describedaclosedcircuit(thePapezcircuit),whichlinkedthehippocampuswiththecingulatecortex,viathemammillarybodiesandanteriorthalamus.
LIMBICSYSTEM
AsummaryofthesimplifiedconnectionsofthelimbicsystemisexpressedbythePapezcircuit.
ThePapezcircuitoversimplifiestheroleofthelimbicsysteminmodulatingfeelings,suchasfear,anxiety,sadness,happiness,sexualpleasure,andfamiliarity.
Arbitrarily,thePapezcircuitbeginsandendsinthehippocampus.Axonsofhippocampalpyramidalcellsconvergetoformthefimbriaand,finally,thefornix.Thefornixprojectsmainlytothemammillarybodiesinthehypothalamus.
LIMBICSYSTEM
Themammillarybodies,inturn,projecttotheanteriornucleusofthethalamusbywayofthemammillothalamictract.Theanteriornucleiprojecttothecingulategyrusthroughtheanteriorlimboftheinternalcapsule,andthecingulategyruscommunicateswiththehippocampusthroughthecingulumandentorhinalcortex.
Theamygdalafunctionstoattachanemotionalsignificancetoastimulusandhelpsimprinttheemotionalresponseinmemory.
LIMBICSTRUCTURESANDFUNCTION• Hippocampalformation(hippocampus,dentategyrus,the
subiculum,andentorhinalcortex)• Amygdala• Septalnuclei• Thehippocampusisimportantinlearningandmemory.The
amygdalaattachesanemotionalsignificancetoastimulusandhelpsimprinttheemotionalresponseinmemory.
LIMBICSYSTEM
LIMBICCONNECTIONSThelimbicsystemisinterconnectedwithanterioranddorsomedialnucleiofthethalamusandthemammillarybodies.Thecingulategyrusisthemainlimbiccorticalarea.Limbic-relatedstructuresalsoprojecttowideareasoftheprefrontalcortex.Centralprojectionsofolfactorystructuresreachpartsofthetemporallobeandtheamygdala.
LIMBICSYSTEM
THEPAPEZCIRCUITincludesthefollowinglimbicstructures:• hippocampalformation,whichprojectsthroughthefornixtothe
mamillarynucleusandseptalarea• mamillarynucleus• anteriorthalamicnucleus• cingulategyrus(Brodmann’sareas23and24)• entorhinalarea(Brodmann’sarea28)
LIMBICSYSTEM
THEPAPEZCIRCUIT:• originatesinthehippocampus• runsviathefornix• entersthemammillarynucleiinthehypothalamus• runsfurtherviathemammillothalamictract• enterstheanteriorthalamicnucleus• projectstothecingulategyrusandorbitofrontalassociationcortex• runsviathecingulum(pathwaywithinthecingulategyrus)• intotheentorhinalcortex• thenthecircuitterminatesinthesubiculumandhippocampus
LIMBICSYSTEM
ANTEROGRADEAMNESIABilateraldamagetothemedialtemporallobesincludingthehippocampusresultsinaprofoundlossoftheabilitytoacquirenewinformation,knownasanterogradeamnesia.KORSAKOFFSYNDROMEAnterogradeamnesiaisalsoobservedinpatientswithKorsakoffsyndrome.KorsakoffsyndromeisseenmainlyinalcoholicswhohaveathiaminedeficiencyandoftenfollowsanacutepresentationofWernickeencephalopathy.Wernickeencephalopathypresentswithocularpalsies,confusion,andgaitataxiaandisalsorelatedtoathiaminedeficiency.InWernicke-Korsakoffsyndrome,lesionsarealwaysfoundinthemammillarybodiesandthedorsomedialnucleiofthethalamus.
LIMBICSYSTEM
Threeconcentricmembranes,theMENINGES,envelopthebrainandspinalcord.
MENINGES
Theyprovidesupportandprotectionforthedelicatetissuestheysurround.
The3individuallayers,inorderfromoutsidetoinside,aretheduramater,arachnoidmaterandpiamater.
DURAMATER(DURA):tough,thickfibrouscoatwhichincompletelydividesthecranialcavityintocompartmentsandaccommodatestheduralvenoussinuses.unlikethespinaldura,consistsof2layers(periostealandmeningeal)thatarefusedtogetherduringmostoftheircourseinthecranialcavity
MENINGES
DURAMATER(DURA)Periosteallayer:Thisouterlayerlinestheinnersurfacesoftheflatbonesandservesastheirperiosteum.Theperiosteallayercaneasilybepeeledawayfromthebones.Meningeal(truedura)layer:Thisistheinnermostlayerthatismostlyfusedwiththeperiostealduramaterthroughoutthecranialcavity.Meningeal(truedura)layer:Atcertainpointsinthecranium,themeningeallayerseparatesfromtheperiosteallayerandformstheduralvenoussinusesandconnectivetissuefoldingsorduplications:falxcerebri,diaphragmasellaeandtentoriumcerebelli.TheseduplicationsseparateandsupportdifferentpartsoftheCNS.
MENINGES
THECRANIALDURAMATER(DURA)Theduralinfoldingsdividethecranialcavityintocompartments,formingpartialpartitions(duralsepta)betweencertainpartsofthebrainandprovidingsupportforotherparts.
MENINGES
Theduralinfoldingsincludethe:• Falxcerebri(cerebralfalx)• Tentoriumcerebelli(cerebellartentorium)• Falxcerebelli(cerebellarfalx)• Diaphragmasellae(sellardiaphragm)
THECRANIALDURAMATER(DURA)Thefalxcerebriisthelargestduralinfolding,liesinthelongitudinalcerebralfissurethatseparatestherightandtheleftcerebralhemispheres.Thefalxcerebriattachesinthemedianplanetotheinternalsurfaceofthecalvaria,fromthefrontalcrestofthefrontalboneandcristagallioftheethmoidboneanteriorlytotheinternaloccipitalprotuberanceposteriorly.Thefalxcerebriendsbybecomingcontinuouswiththetentoriumcerebelli.
MENINGES
THECRANIALDURAMATER(DURA)Thetentoriumcerebelliisawidecrescenticseptumthatseparatestheoccipitallobesofthecerebralhemispheresfromthecerebellum.Thetentoriumcerebelliattachesrostrallytotheclinoidprocessesofthesphenoid,rostrolaterallytothepetrouspartofthetemporalbone,andposterolaterallytotheinternalsurfaceoftheoccipitalboneandpartoftheparietalbone.Thefalxcerebelliisaverticalduralinfoldingthatliesinferiortothetentoriumcerebelliintheposteriorpartoftheposteriorcranialfossaandpartiallyseparatesthecerebellarhemispheres.
MENINGES
THECRANIALDURAMATER(DURA)Thediaphragmasellaeissuspendedbetweentheclinoidprocessesformingapartialroofoverthehypophysialfossainthesphenoidandcoversthepituitaryglandinthisfossa.
MENINGES
ARACHNOIDMATER(ARACHNOID)Itismuchthinnerthantheduraandismostlytranslucent.Itsurroundsthebrainloosely,spanningoverdepressionsandconcavities.Projectionsofarachnoidcalledarachnoidgranulationspenetratethroughtheduramaterandextendintothesuperiorsagittalduralvenoussinus.ArachnoidgranulationsarewhereCSFreturnstothesystemicvenouscirculation.
MENINGES
PIAMATER(PIA)Delicateinternalvasculatedlayer,microscopicallythin,membranewhichfollowsthecontoursofthebrainandiscloselyadherenttoitssurface.Tightlyinveststhesurfacesofthebrainandcannotbedissectedaway,havingthesamerelationshipwiththebrainasspinalpiamater
MENINGES
THEMENINGES:1.Duramater(dura):tough,thickfibrouscoatwhichincompletelydividesthecranialcavityintocompartmentsandaccommodatestheduralvenoussinuses.2.Arachnoidmater(arachnoid):ismuchthinnerthantheduraandismostlytranslucent.Itsurroundsthebrainloosely,spanningoverdepressionsandconcavities.3.Piamater(pia):delicateinternalvasculatedlayer,microscopicallythin,membranewhichfollowsthecontoursofthebrainandiscloselyadherenttoitssurface.
MENINGES
THEARACHNOIDANDPIAMATERThearachnoidmaterandthepiamatertogetheraresometimesreferredtoastheleptomeninges.
Theduraisseparatedfromthearachnoidbyanarrowsubduralspace.
MENINGES
Thearachnoidisseparatedfromthepiabythesubarachnoidspace,whichvariesgreatlyindepth;thelargerexpansesaretermedsubarachnoidcisterns,whichcontainscerebrospinalfluid(CSF).
Theduraisseparatedfromthearachnoidbyanarrowsubduralspace.Thearachnoidisseparatedfromthepiabythesubarachnoidspace,whichvariesgreatlyindepth;thelargerexpansesaretermedsubarachnoidcisterns,whichcontainscerebrospinalfluid(CSF).
Thecerebrospinalfluid(CSF)isformedbythechoroidplexusesofthefourventriclesofthebrain.
MENINGES
Thecerebrospinalfluid(CSF)leavestheventricularsystemandentersthesubarachnoidspacebetweenthearachnoidandpiamater.
SPACESRELATEDTOTHECRANIALMENINGESEpiduralspaceisapotentialspacebetweentheperiostealduraandthebonesoftheskull:siteofepiduralhematomas.Subduralspaceisthepotentialspacebetweenthemeningealduraandthearachnoidmembrane:siteofsubduralhematomas.SubarachnoidspaceliesbetweenthearachnoidandpiamatercontainingCSF:siteofsubarachnoidhemorrhage.
MENINGES
EPIDURALHEMATOMAAnepiduralhematomaresultsfromtraumatothelateralaspectoftheskullwhichlaceratesthemiddlemeningealartery.Arterialhemorrhageoccursrapidlyintheepiduralspacebetweentheperiostealduraandtheskull.
MENINGES
EXTRADURALHAEMATOMASeparationofthedurafromtheunderlyingperiosteumrequiressignificantforce,andconsequentlyoccursonlywhenhigh-pressurearterialbleedingoccursintothevirtualspace.
EPIDURALHEMATOMAEpiduralhemorrhageformsalens-shaped(biconvex)hematomaatthelateralhemisphere.Epiduralhematomaisassociatedwithamomentarylossofconsciousnessfollowedbyalucid(asymptomatic)periodofupto48hours.Patientsthendevelopsymptomsofelevatedintracranialpressuresuchasheadache,nausea,andvomiting,combinedwithneurologicalsignssuchashemiparesis.Herniationofthetemporallobe,coma,anddeathmayoccurrapidlyifthearterialbloodisnotevacuated.
MENINGES
SUBDURALHEMATOMAAsubduralhematomaresultsfromheadtraumathattearssuperficial(“bridging”)cerebralveinsatthepointwheretheyenterthesuperiorsagittalsinus.Asubduralhemorrhageoccursbetweenthemeningealduraandthearachnoid.
MENINGES
Subduralhemorrhageformsacrescent-shapedhematomaatthelateralhemisphere.Largesubduralhematomasresultinsignsofelevatedintracranialpressuresuchasheadacheandnausea.Smallorchronichematomasareoftenseeninelderlyorchronicalcoholicpatients.Overtime,herniationofthetemporallobe,coma,anddeathmayresultifthevenousbloodisnotevacuated.
SUBARACHNOIDHEMORRHAGEAsubarachnoidhemorrhageresultsfromaruptureofaberryaneurysminthecircleofWillis.ThemostcommonsiteisintheanteriorpartofthecircleofWillisatthebranchpointoftheanteriorcerebralandanteriorcommunicatingarteries.Othercommonsitesareintheproximalpartofthemiddlecerebralarteryoratthejunctionoftheinternalcarotidandposteriorcommunicatingarteries.Typicalpresentationassociatedwithasubarachnoidhemorrhageistheonsetofasevereheadache.
MENINGES
EXTRADURALHAEMATOMAThiscanresultfromdamagetoanyarterialvessel,commonlyfollowingskullfracture.
MENINGES
EXTRADURALHAEMATOMATheclassicsiteforsuchinjuryisalongthecourseofthemiddlemeningealartery,whereadirectblowcausingabonefracturecanrupturethearteryandcauserapidcollectionofanextraduralhaematoma.
EXTRADURALHAEMATOMAThehaematomaisunderconsiderablepressurebecauseofthearterialbloodpressurefeedingitandtheresistanceofferedbythestrongadhesionbetweenduraandperiosteum.
SUBDURALHAEMATOMAThecharacteristicsofasubduralhaematomadifferfromtheextraduralhaematoma.Clinicallytheaccumulationisoftenofrelativelylowpressureandseldompresentsasamedicalemergency:evensizeableaccumulationsmaybetoleratedonachronicbasiswithmildornosymptoms.
MENINGES
BASALGANGLIAThesecompactmassesofgreymatteraresituateddeepinthesubstanceofthecerebralhemisphere.Thesecompactmassesofgreymattercomprisethecorpusstriatum(composedofthecaudatenucleus,theputamenandtheglobuspallidus)andtheclaustrum.Togetherwiththecerebellum,theyareinvolvedinco-ordinationandcontrolofmovement.Thetermbasalgangliaisusedtodenoteanumberofsubcorticalnuclearmassesthatlieintheinferiorpartofthecerebralhemisphere,incloserelationwiththeinternalcapsule
BASALGANGLIA
BASALGANGLIAThetraditionaldefinitionofthebasalgangliaincludedthecorpusstriatum,claustrum,andamygdaloidcomplex.Thecorpusstriatumconsistsofthecaudatenucleus,putamenandglobuspallidusBecauseoftheircloseproximity,theputamenandglobuspalliduswereonceconsideredasthelentiform(lenticular)complexornucleus.Theputamenandcaudatenucleusshareacommonchemocytoarchitectureandconnections,andtheyarereferredtojointlyastheneostriatumorsimplythestriatum.
BASALGANGLIA
GROUPINGOFTHEBASALNUCLEI(GANGLIA)Thestriatumconsistsofthecaudatenucleusandputamen.Thelentiformnucleusconsistsoftheglobuspallidusandputamen.Thecorpusstriatumconsistsofthelentiformnucleusandcaudatenucleus.Theclaustrumliesbetweenthelentiformnucleusandtheinsularcortex.
BASALGANGLIA
Thecaudatenucleusisalargehomogeneousmassofgreymatterconsistingofahead,anteriortotheinterventricularforamenandformingthelateralwalloftheanteriorhornofthelateralventricle;abody,formingthelateralwallofthebodyoftheventricle;andanelongatedtail,whichformstheroofoftheinferior(temporal)hornoftheventricle.
BASALGANGLIA
Thecaudatenucleusislargelyseparatedfromtheputamenbytheinternalcapsule,butthetwostructuresareconnectedanteriorly.
Theputamenisaroughlyovoidmasscloselyappliedtothelateralaspectoftheglobuspallidus;together,theyarecalledthelentiformnucleus.
BASALGANGLIA
Thecorpusstriatumreceivesafferentconnectionsfromthecerebralcortexandsendsefferentstotheglobuspallidus.Fromthere,fibresprojecttothethalamusand,thence,backtothepremotorcortex.
Thebasalgangliaplayimportantmotorfunctionsinstartingandstoppingvoluntarymotorfunctionsandinhibitingunwantedmovements.
BASALGANGLIA
Thebasalgangliaconsistsof3nucleimassesdeepinthecerebrum(caudatenucleus,putamen,andglobuspallidus),onenucleusinthemidbrain(substantianigra),andthesubthalamicnucleusofthediencephalon.
Thestriatumcombinesthecaudatenucleusandtheputamenwhilethecorpusstriatumconsistsofthese2nucleiplustheglobuspallidus.
Thereare2parallelcircuits(directandindirect)throughthebasalganglia.Thesecircuitsreceiveextensiveinputfromthecerebralcortexthatprojectbacktothemotorcortexafterarelayintheventrolateral(VL)nucleusofthethalamus.Bothofthesepathwaysdemonstratedisinhibition.Thedirectpathwayincreasesthelevelofcorticalexcitationandpromotesmovement.Theindirectpathwaydecreasesthelevelofcorticalexcitationandsuppressesunwantedmovement.Allbasalgangliaconnectionsarewithipsilateralcortex.
BASALGANGLIA
THEDISORDERSOFTHEBASALGANGLIA:Disordersofthebasalgangliaareprincipallycharacterizedbyabnormalitiesofmovement,muscletoneandposture.
BASALGANGLIA
THEDISORDERSOFTHEBASALGANGLIA:-aninabilitytoinitiateandexecutewantedmovements(asinParkinson’sdisease)-aninabilitytopreventunwantedmovements(asinHuntington’sdisease).
THEDISORDERSOFTHEBASALGANGLIA:PARKINSONDISEASEClinicalManifestations:bradykinesia,cogwheelrigidity,pill-rolling(resting)tremor,shufflinggate,stoopedposture,maskedface,depression,dementia
BASALGANGLIA
THEDISORDERSOFTHEBASALGANGLIA:HUNTINGTONDISEASEClinicalManifestations:chorea(multiple,rapid,randommovements),athetosis(slow,writhingmovements),personalitychanges,dementia.Onset:20−40years.