NERVOUS SYSTEM: THE BRAIN Human Anatomy Unit 4
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