NERVOUSSYSTEM:THEBRAIN

HumanAnatomyUnit4

InAnatomyToday

VentriclesoftheBrain

• Lateralventricles– 2ventriclesshapedlike“ramhorns”– Separatedbytheseptumpellucidum

• Thirdventricle– Surroundsthalamusdiencephalonandbrainstem

• Fourthventricle– Anteriortocerebellum– Contains3aperturesleadingtothe“subarachnoidspace”

v Cerebralaqueduct– Canalbetweenthirdandfourthventricle

VentriclesoftheBrain

CerebrospinalFluid(CNS)• Ventricleslinedwith

choroidplexus– Ependymalcells– Producecerebrospinalfluid

(CSF)– Produces500ml/day– 150mLincirculation

• SurroundsandbathesexposedsurfacesoftheCNS– Preventsfriction– Support– Regulationof

microenvironment

CirculationofCSF

• CSFcirculatesthroughoutventricles,subarachnoidspaceandcentralcanal

• CSFisreturnedtogeneralcirculation– Arachnoidgranulations

– Projectintotheduralsinus

CirculationofCSF

TheCranialMeninges

CranialMeningesDuraMater

• “Toughmother”– Denseirregularconnectivetissue

– Outermostmeninge• outer=periosteallayer• inner=meningeallayer

– “falxcerebri”

– 2layersformaspacebetweenwhicharetheduralsinuses

CranialMeningesArachnoidandPiaMater

• “Spiderymother”• Arachnoidgranulations– forreturnofCSFtogeneralcirculation

• “Delicatemother”• Indissectablefromsurfaceofthebrain

• Looseconnectivetissue

FalxCerebri

Falx cerebri is formed as an extension of the meningeal layer of the dura mater

BloodVesselsoftheBrain

InternalcarotidarteriesVertebralarteries

JugularveinsDraintheduralsinuses

MajorDivisionsoftheBrain

Cerebrum• Cerebralhemispheres

– Leftandrighthalves– Separatedbylongitudinal

fissure– Connectedbytracts

• Dividedintofunctionallobes

• Contain“higherbraincenters”– Nucleiresponsibleformotor

coordinationandcontrolofmemory,emotionandotherfunctions

CerebralCortex

• GrayMatter• Gyrus(gyrip.)– foldsofthecerebralsurface

• Sulcus(sulcip.)– groovesbetweengyri

• Fissure– deepgroove

TheCerebralLobes

• 5majordivisionsineachhemisphere

• 4namedafterbonesunderwhichtheylie– Frontal– Parietal– Occipital– Temporal

• 1oninterior– Insula

FrontalLobe• Amotorcortex• Pre-centralgyrusiswherethe

primarymotorcortexislocated– Controlsvoluntarymovements

• AlsomadeupofmostlyDopaminesensitiveneurons– Shorttermmemory– Reward– Learning– Emotions– Motivation

• Majormotorpathwayisthecorticospinaltract

ParietalLobe

• SensoryCortex• Thepostcentralgyrusiswherethesomato-sensorycortexislocated– Involvedinintegratingsensoryinformation• Skin• Proprioception

• Languageprocessing

OccipitalLobe

• Mapsmostlytotheoccipitalbone

• Isthevisualcortex– Receives,integratesandprocessesvisualinformation

– ClinicallyreferredtoasBrodmannarea17

TemporalLobe

• Auditorycortex• Processesvisualinformationintomemories

• Languagecomprehension

• Emotionassociations• Declarative(long-term)memory– Factsandevents

Insula

• Smalllobesdeepinlateralsulcusbeneathtemporallobes

• Involvedinconsciousness– Emotion,homeostasis,selfawareness,cognitivefunctioning

• Gustatorycortex

New study suggests that the insula is involved in smoking addiction…

CerebralMedulla

• Myelinatedaxons=whitematter• ArrangedintotractsconnectingdifferentpartsoftheCNS

• Associationtracts– Connectregionsofcortexwithinsamehemisphere

• Commissuraltracts– Bridgesbetweencerebralhemispheres– Ex)corpuscallosum

• Projectiontracts– Betweencerebralcortex,caudalbrain,andspinalcord

CerebralWhiteMatter

BasalNuclei

• Paired,irregularmassesofgraymatter

• Connectedtocerebrum,thalamus,brainstem

• Involvedin– Motorprograms– Procedurallearning– Routinebehaviorsorhabits

– Eyemovements– Emotion

LimbicSystem

• Largegroupofnucleithroughoutdifferentpartsofthebrain

• Responsibleforcontrolof– Emotion– Sexdrive– Aggression–Memoryconsolidation...amongotherfunctions

• Hippocampus– Responsibleformemoryconsolidation

LimbicSystem

Diencephalon

• “in-between” brain• Components– Epithalamus– Thalamus

• PairedR/L

– Hypothalamus

Epithalamus• Connectsthelimbicsystemtootherpartsofthebrain

• Covers3rd ventricle• Posteriorportion– Pinealgland

• Melatonin• Circadianrhythms

– Habenularnucleus• Relaystationforlimbicsystem

• Visceralandemotionalresponsetoodors

Thalamus

• Clustersofnucleiorganizedintogroups

• Majorrelaystationforsensoryinformation

• Graymatteronbothsidesofthirdventricle

Hypothalamus

• Containsmanydiversenucleicontrolling– Bodytemperature– Sexdrive– Feeding– Drinking– Thirstsensation– Pituitarysecretions

• Formstheinferiorwallsofthethirdventricle

BrainStem

• Connectsforebrain(cerebrum,diencephalon)andcerebellumtospinalcord

• 3parts– Midbrain– Pons– Medullaoblongata

Midbrain

• CorporaQuadrigemina– Superiorcolliculus– Inferiorcolliculus

• Cerebralpeduncles• Nucleiinvolvedin:– vision,hearing– sleep/wakecycles– Alertness– Bodytemperatureregulation

– Motorprograms

Pons• Containssensoryandmotor

tracts• Relaysignalsfromcerebrum

anddiencephalontothecerebellum

• Autonomicnuclei– Sleep,respiration,

swallowing,bladdercontrol,hearing,equilibrium,taste,eyemovement,facialexpressions,facialsensationandposture

– Playsaroleindreaming• Originforcranialnerves

V-VIII

MedullaOblongata

• Theinferiormostregionofthebrainstem

• Autonomiccenters– Respiration,vomiting,sneezing,cardiovascularfunctions

• Medullarypyramidshousethepyramidaltracts– Decussationofthepyramids

• OrigincranialnervesIX-XII

TheCerebellum• Secondlargestsingle

structureofthebrain• Threelobes• Arborvitae

– “thetreeoflife”– Whitematterofthe

cerebellum

• Folia• Involvedinmotorcontrolof

coordination,timingandprecisionofskeletalmuscleactivity

HistologyoftheCerebellum• Whitematter(medulla)

– Myelinatednervefibers

• Graymatter(cortex)– Granularlayer

• Granulecells– Smallestneuronsandmost

numerousneuronsinthebrain

– Purkinjelayer• Purkinjecells

– Processesformthedendritrictreeofthemolecularlayer

– >200synapses

– Molecularlayer• Dendritictree