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HumanAnatomy
Unit4
NERVOUSSYSTEM:
THEBRAIN
InAnatomyToday
VentriclesoftheBrain
• Lateralventricles
– 2ventriclesshapedlike“ramhorns”
– Separatedbytheseptumpellucidum
• Thirdventricle
– Surroundsthalamusdiencephalonandbrainstem
• Fourthventricle
– Anteriortocerebellum
– Contains3aperturesleadingtothe“subarachnoid
space”
v Cerebralaqueduct
– Canalbetweenthirdandfourthventricle
VentriclesoftheBrain
CerebrospinalFluid(CNS)
• Ventricleslinedwith
choroidplexus
– Ependymalcells
– Producecerebrospinalfluid
(CSF)
– Produces500ml/day
– 150mLincirculation
• Surroundsandbathes
exposedsurfacesoftheCNS
– Preventsfriction
– Support
– Regulationof
microenvironment
CirculationofCSF
• CSFcirculates
throughout
ventricles,
subarachnoidspace
andcentralcanal
• CSFisreturnedto
generalcirculation
– Arachnoid
granulations
– Projectintothe
duralsinus
CirculationofCSF
TheCranialMeninges
CranialMeninges
DuraMater
• “Toughmother”
– Denseirregular
connectivetissue
– Outermostmeninge
• outer=periosteallayer
• inner=meningeallayer
– “falxcerebri”
– 2layersformaspace
betweenwhicharethe
duralsinuses
CranialMeninges
ArachnoidandPiaMater
• “Spiderymother”
• Arachnoidgranulations
– forreturnofCSFto
generalcirculation
• “Delicatemother”
• Indissectablefrom
surfaceofthebrain
• Looseconnectivetissue
FalxCerebri
Falx cerebri is formed as an extension of the meningeal layer of the dura mater
BloodVesselsoftheBrain
Jugularveins
Draintheduralsinuses
Internalcarotidarteries
Vertebralarteries
MajorDivisionsoftheBrain
Cerebrum
• Cerebralhemispheres
– Leftandrighthalves
– Separatedbylongitudinal
fissure
– Connectedbytracts
• Dividedintofunctional
lobes
• Contain“higherbrain
centers”
– Nucleiresponsibleformotor
coordinationandcontrolof
memory,emotionandother
functions
CerebralCortex
• GrayMatter
• Gyrus(gyrip.)
– foldsofthecerebral
surface
• Sulcus(sulcip.)
– groovesbetweengyri
• Fissure
– deepgroove
TheCerebralLobes
• 5majordivisionsin
eachhemisphere
• 4namedafterbones
underwhichtheylie
–
–
–
–
Frontal
Parietal
Occipital
Temporal
• 1oninterior
– Insula
FrontalLobe
•
•
Amotorcortex
Pre-centralgyrusiswherethe
primarymotorcortexislocated
– Controlsvoluntarymovements
•
Alsomadeupofmostly
Dopaminesensitiveneurons
–
–
–
–
–
•
Shorttermmemory
Reward
Learning
Emotions
Motivation
Majormotorpathwayisthe
corticospinaltract
ParietalLobe
• SensoryCortex
• Thepostcentralgyrusis
wherethesomatosensorycortexis
located
– Involvedinintegrating
sensoryinformation
• Skin
• Proprioception
• Languageprocessing
OccipitalLobe
• Mapsmostlytothe
occipitalbone
• Isthevisualcortex
– Receives,integratesand
processesvisual
information
– Clinicallyreferredtoas
Brodmannarea17
TemporalLobe
• Auditorycortex
• Processesvisual
informationinto
memories
• Language
comprehension
• Emotionassociations
• Declarative(long-term)
memory
– Factsandevents
Insula
• Smalllobesdeepin
lateralsulcusbeneath
temporallobes
• Involvedin
consciousness
– Emotion,homeostasis,
selfawareness,cognitive
functioning
• Gustatorycortex
New study suggests that the insula is involved in smoking addiction…
CerebralMedulla
• Myelinatedaxons=whitematter
• Arrangedintotractsconnectingdifferentpartsof
theCNS
• Associationtracts
– Connectregionsofcortexwithinsamehemisphere
• Commissuraltracts
– Bridgesbetweencerebralhemispheres
– Ex)corpuscallosum
• Projectiontracts
– Betweencerebralcortex,caudalbrain,andspinalcord
CerebralWhiteMatter
BasalNuclei
• Paired,irregularmasses
ofgraymatter
• Connectedto
cerebrum,thalamus,
brainstem
• Involvedin
– Motorprograms
– Procedurallearning
– Routinebehaviorsor
habits
– Eyemovements
– Emotion
LimbicSystem
• Largegroupofnucleithroughoutdifferent
partsofthebrain
• Responsibleforcontrolof
– Emotion
– Sexdrive
– Aggression
– Memoryconsolidation...amongotherfunctions
• Hippocampus
– Responsibleformemoryconsolidation
LimbicSystem
Diencephalon
• “in-between” brain
• Components
– Epithalamus
– Thalamus
• PairedR/L
– Hypothalamus
Epithalamus
• Connectsthelimbic
systemtootherpartsof
thebrain
• Covers3rd ventricle
• Posteriorportion
– Pinealgland
• Melatonin
• Circadianrhythms
– Habenularnucleus
• Relaystationforlimbic
system
• Visceralandemotional
responsetoodors
Thalamus
• Clustersofnuclei
organizedinto
groups
• Majorrelaystation
forsensory
information
• Graymatteronboth
sidesofthird
ventricle
Hypothalamus
• Containsmanydiverse
nucleicontrolling
–
–
–
–
–
–
Bodytemperature
Sexdrive
Feeding
Drinking
Thirstsensation
Pituitarysecretions
• Formstheinferiorwalls
ofthethirdventricle
BrainStem
• Connectsforebrain
(cerebrum,
diencephalon)and
cerebellumtospinal
cord
• 3parts
– Midbrain
– Pons
– Medullaoblongata
Midbrain
• CorporaQuadrigemina
– Superiorcolliculus
– Inferiorcolliculus
• Cerebralpeduncles
• Nucleiinvolvedin:
vision,hearing
sleep/wakecycles
Alertness
Bodytemperature
regulation
– Motorprograms
–
–
–
–
Pons
• Containssensoryandmotor
tracts
• Relaysignalsfromcerebrum
anddiencephalontothe
cerebellum
• Autonomicnuclei
– Sleep,respiration,
swallowing,bladdercontrol,
hearing,equilibrium,taste,
eyemovement,facial
expressions,facialsensation
andposture
– Playsaroleindreaming
• Originforcranialnerves
V-VIII
MedullaOblongata
• Theinferiormostregion
ofthebrainstem
• Autonomiccenters
– Respiration,vomiting,
sneezing,cardiovascular
functions
• Medullarypyramids
housethepyramidal
tracts
– Decussationofthe
pyramids
• Origincranialnerves
IX-XII
TheCerebellum
• Secondlargestsingle
structureofthebrain
• Threelobes
• Arborvitae
– “thetreeoflife”
– Whitematterofthe
cerebellum
• Folia
• Involvedinmotorcontrolof
coordination,timingand
precisionofskeletalmuscle
activity
HistologyoftheCerebellum
• Whitematter(medulla)
– Myelinatednervefibers
• Graymatter(cortex)
– Granularlayer
• Granulecells
– Smallestneuronsandmost
numerousneuronsinthe
brain
– Purkinjelayer
• Purkinjecells
– Processesformthe
dendritrictreeofthe
molecularlayer
– >200synapses
– Molecularlayer
• Dendritictree