The Brain

Central Nervous System

1. THE BRAIN
Mr.Binu Babu
Asst.Professor
Mrs.JincyEalias
Asst.Professor

2. •Thebrainisoneofthemostcomplexand
magnificentorgansinthehumanbody.
Braingivesusawarenessofourselvesand
ourenvironment,processingaconstant
streamofsensorydata.
•Itcontrolsmusclemovements,the
secretionsofglands,andevenbreathingand
internaltemperature.

4. The Brain: Embryonic development
•Embryonicdevelopmentofthehuman
brain.
–Formedbyweek4,theneuraltubequickly
subdividesintotheprimarybrainvesicles,
whichsubsequentlyformthesecondarybrain
vesiclesbyweek5.Thesefivevesicles
differentiateintotheadultbrainstructures.The
adultstructuresderivedfromtheneuralcanal.

5. •Thebrainandspinalcordbeginasanembryonic
structure
•calledtheneuraltube.Theneuraltubeforms,its
anterior(rostral)endbeginstoexpandand
constrictions
•appearthatmarkoffthethreeprimarybrain
vesicles
–Prosencephalonorforebrain
–Mesencephalonormidbrain
–Rhombencephalonorhindbrain
•The remaining caudal (“toward the tail”), or
posterior, portion of the neural tube becomes the
spinal cord.

7. Human Brain
•The major components
of the brain are
–The cerebrum
–The cerebellum
–The brainstem

8. Cerebrum
•Thecerebrumisthelargestandmost
developmentallyadvancedpartofthe
humanbrain.Itisresponsibleforseveral
higherfunctions,includinghigher
intellectualfunction,speech,emotion,
integrationofsensorystimuliofalltypes,
initiationofthefinalcommonpathwaysfor
movement,andfinecontrolofmovement.

9. Cerebrum Cerebrum
Cerebellum
Cerebrum

10. Cerebral hemispheres
•Thecerebrumisdividedintoa
rightandalefthemispheres.
•Thelefthemispherecontrolsthe
majorityoffunctionsontheright
sideofthebody,whiletheright
hemispherecontrolsmostof
functionsontheleftsideofthe
body
•Thecrossingofnervefiberstakes
placeinthebrainstem.Thus,
injurytotheleftcerebral
hemisphereproducessensoryand
motordeficitsontherightside,
andviceversa.

11. Lobes of the Cerebrum
Fissures (deep
grooves)dividethe
cerebrumintolobes
Cerebrum is
composedofpairsof
Frontallobe
Parietallobe
Occipitallobe
Temporallobe

12. External features:
Gyri–Elevated ridges “winding” around the brain.
Sulci–Small grooves dividing the gyri
–Central Sulcus–Divides the frontal lobe from the parietal
lobe.
–Lateral sulcus-outlines the flapliketemporal lobe and
separates it from the parietal and frontal lobes.
Fissures–Deep grooves, generally dividing large
regions/lobes of the brain
•Transverse Fissure–Separates the cerebrum from the
cerebellum.
•Longitudinal Fissure–Divides the two cerebral
hemispheres
•Sylvian/Lateral Fissure–Divides the temporal lobe from
the frontal and parietal lobes

13. Gyrus

14. Sulcus

15. Surfaces

16. Boarders of cerebral hemispheres

17. Poles of Brain

18. Regions of cerebral hemisphere
Cerebral hemisphere has three basic regions:
1.A superficial cerebral cortex of gray matter,
which looks gray in fresh brain tissue
2.Internal white matter
3.Basal nuclei, islands of gray matter situated
deep within the white matter

19. Grey matter
•Itisamajorcomponent
ofthecentralnervous
system consisting
of neuronal cell
bodies, neuropil
(dendritesandmyelinat
ed aswellas
unmyelinatedaxons)
glialcells(astrocytes
andoligodendrocytes)
synapsesandcapillaries.

20. Grey matter in thespinal cord
•Greymatterinthespinalcordisknownasthegrey
columnwhichtravelsdownthespinalcord
distributedinthreegreycolumnsthatarepresented
inan"H"shape.
•Theforward-facingcolumnistheanteriorgrey
column
•Therear-facingoneistheposteriorgreycolumn
•Theinterlinkingoneisthelateralgreycolumn.
•Thegreymatterontheleftandrightsideis
connectedbythegreycommissure.
•Thegreymatterinthespinalcordconsists
ofinterneurons,aswellascellbodies.

21. Cerebral cortex
•Thecerebralcortexisthe“executivesuite”ofthe
nervoussystem.
•Itenablesustobeawareofourselvesandour
sensations,tocommunicate,remember,understand
andinitiatevoluntarymovements.
•Thecerebralcortexiscomposedofgraymatter:
neuroncellbodies,dendrites,associatedgliaand
bloodvessels,butnofibertracts.
•Itcontainsbillionsofneuronsarrangedinsixlayers.
•2–4mm(about1/8inch)thick
•Itaccountsforroughly40%oftotalbrainmass.

23. •Based on the differences in lamination the
cerebral cortex can be classified into two
parts
–The large area ofneocortex
–The smaller area ofallocortex

24. Neocortex
•The neocortex(also known as the isocortexor
neopallium) is the part of the mature cerebral
cortex with six distinct layers.

26. Neocortex-Layers

27. Allocortex
•The allocortexis the part of the cerebral
cortex with less than six layers and has
three regions,
–Thepaleocortexwith three cortical laminae
–Thearchicortexwhich has four or five cortical
laminae
–Theperiallocortex–a transitional zone
between the neocortexand the allocortex

28. White matter
•Thewhitematterisa
networkoffibersthat
enablesregionsofthe
braintocommunicate
witheachother.

29. •White matter consists largely of myelinated
fibers bundled into large tracts. These fibers
and tracts are classified according to the
direction in which they run as
–Association Fibers
–Projection Fibers
–Commissural Fibers

31. •Association fibers: Connects different cortical
areas of the same hemisphere to one another.
–Eg:-superior longitudinal fasciculus
•Projectionfibers:Connectscerebralcortexto
otherpartsofCNSlikebrainstemandspinal
cord.
–Eg:coronaRadiata,internalcapsule
•Commissural fibers:Connectsthe
correspondingpartsoftwohemispheres

32. White Matter of Cerebral
hemisphere
•Association tracts (fibers)-different regions
in cerebral cortex.
•Projection tracts (fibers)-cerebral cortex
other masses of gray matter.
•Commissuresfibers -R L.

33. Internal capsule
•Internalcapsuleis
locatedbetweenthe
lentiform nucleus
laterally and
thethalamusand
caudate nucleus
medially.
•Inahorizontalsectionof
cerebralhemisphere,the
internalcapsuleappears
asaV-shapedbundleof
fiberswiththeapex
directedmedially.

35. Theinternalcapsuleisdividedintofiveparts.
–Anteriorlimb:partoftheinternalcapsulethatliesbetweenthe
anteriorpartoflentiformnucleuslaterallyandheadofcaudate
nucleusmedially.
–Genu:Itisthebendbetweentheanteriorandposteriorlimbof
internalcapsule.Theconcavityofthebendfaceslaterally.
–Posteriorlimb:isthatpartofinternalcapsulewhichlies
betweenthethalamusmediallyandtheposteriorpartof
lentiformnucleuslaterally.
–Retrolentiformpart:islocatedposteriortothelentiform
nucleus.
–Sublentiformpart:islocatedinferiortothelentiformnucleus.

37. Internal capsulecontains both themotor
fibers and sensory fibers
Motor/DescendingFibersinInternalcapsule
•Corticopontine:originatefromallthelobesofcerebrumandrelay
inipsilateralpontinenuclei.
•Pyramidalfibers:
–Corticospinal:originatemainlyinprimarymotorcortexand
relayincontralateralanteriorhornofspinalcord.
–Corticonuclear:originatemainlyinprimarymotorcortex
andrelayusuallyincontralateral(somebilateral)motor
nucleiofcranialnerves.
•ExtrapyramidalfibersCoticorubral,corticostriate,corticonigral
fibersetc.:thesefibersoriginateinthemotorandpremotorareasof
cerebralcortexrelayinsubcorticalnucleiviz.rednucleus,corpus
stiatumandsubstantianigrarespectively.

38. Internal Capsule -
Sensory/Ascending Fibers
•Thalmocorticalandcorticothalamicfibers:The
thalamocorticalfibersarethe3rdorderneuronsofascending
pathways.
•The four thalamic radiation bands are:
–Anterior thalamic radiation: Pass anteriorlyto connect the
anterior and dorsomedialnucleus of thalamus to the frontal
lobe.
–Superior thalamic radiation: Pass superiorly to connect the
ventral tier of nucleus of thalamus to primary and premotor
areas of frontal lobe and sensory areas of parietal lobe.
–Posterior thalamic radiation (Optic radiation): pass
posteriorlyto connect the lateral geniculatebody to the
primary visual cortex.
–Inferior thalamic radiation (Auditory radiation): pass
inferiorly and laterally to connect the medial geniculatebody
to the primary auditory area.

40. Arrangement of Descending (Motor)
and Ascending (Sensory) Fibers
Anterior limb:
Motor
•Frontopontine fibers
Sensory
•Anterior thalamic radiation
Genu
Motor
•Frontopontinefibers,
•Corticonuclear
•Corticospinalfibers for head
and neck
Sensory
•Superior thalamic radiation
Retorlentiformpart
Motor
•Parietopontine
•Occipitopontinefibers
Sensory
•Posterior thalamic ( Optic)
radiation
Sublentiformpart
Motor
•Parietopontine
•Occipitopontinefibers
Sensory
•Inferior thalamic ( Auditory)
radiation

41. Basal Nuclei
•Deepwithinthecerebralwhitematteristhe
thirdbasicregionofeachhemisphere,agroup
ofsubcorticalnucleicalledthebasalnucleior
basalganglia.
•Basal nuclei include the
–Caudate nucleus
–Putamen
–Globuspallidus
•Thecomma-shapedcaudatenucleusarches
superiorlyoverthediencephalon.Together
withtheputamen,itformsthestriatum

43. •Theputamenandglobuspallidustogether
formalens-shapedmass,sometimescalledthe
lentiformnucleus.
•Thebasalnucleiarefunctionallyassociated
withthesubthalamicnucleiofthediencephalon
andthesubstantianigraofthemidbrain.
•Thebasalnucleireceiveinputfromtheentire
cerebralcortex,aswellasfromother
subcorticalnuclei

45. The substantianigra
•Itisabrainstructure
locatedin the
midbrain,andforms
partofthebasal
ganglia.Itisthelargest
nucleusin the
midbrain.
•Thesubstantianigra
also plays an
importantrolein
rewardandaddiction.

46. Amygdaloidnucleus
•Asmallovalstructureinthetemporal
lobeofthebrainthatiscloselyconnectedto
thehypothalamus,thehippocampus,and
thecingulategyrus.
•Theamygdaloidnucleusispartofthe
olfactoryandlimbicsystemsandplaysa
roleinthesenseofsmell,motivation,and
emotionalbehavior.

49. Ventricles
•Theventriclesarestructuresthat
producecerebrospinalfluid,andtransport
itaroundthecranialcavity.Theyarelined
byependymalcells,whichformastructure
calledthechoroidplexus.Itiswithin
thechoroidplexusthatCSFisproduced.
•Embryologically,theventricularsystemis
derivedfromthelumenoftheneuraltube.
•Therearefourventricles;rightandleftlateral
ventricles,thirdventricleandfourthventricle.

50. Lateral Ventricles
•The left and rightlateral ventriclesare located
within their respective hemispheres of the
cerebrum. Theyhave ‘horns’ which project into the
frontal, occipital and temporal lobes.
•Thepairedlateralventricles,onedeepwithineach
cerebralhemisphere,arelargeC-shapedchambers
thatreflectthepatternofcerebralgrowth.
•Anteriorly,thelateralventricleslieclosetogether,
separatedonlybyathinmedianmembranecalled
theseptumpellucidum.
•Thevolumeofthelateralventriclesincreaseswith
age.

51. Third Ventricle
•Thelateralventriclesareconnectedto
thethirdventriclebytheforamenofMonro.
Thethirdventricleissituatedinbetween
therightandtheleftthalamus.Theanterior
surfaceoftheventriclecontainstwo
protrusions:
–Supra-opticrecess–locatedabovetheoptic
chiasm.
–Infundibularrecess–locatedabovetheoptic
stalk.

52. Fourth Ventricle
•Thefourthventricleisthelastinthesystem–it
receivesCSFfromthethirdventriclevia
thecerebralaqueduct.Itlieswithinthe
brainstem,atthejunctionbetween
theponsandmedullaoblongata.Fromthe4th
ventricle,thefluiddrainsintotwoplaces:
–Centralspinalcanal–Bathsthespinalcord
–Subarachnoidcisterns–Bathsthebrain,between
arachnoidmaterandpiamater.HeretheCSFis
reabsorbedbackintothecirculation.

54. CORPUS CALLOSUM
•Itisthelargestcollection
ofcommissuralfibersof
thecerebrum.
•Itlocatedinthefloorof
themedianlongitudinal
fissureandconnectstwo
cerebral hemisphere
exceptlowerandanterior
partofthetemporallobe.
•Corpuscallosumclosely
relatedtolateralventricle.

55. PARTS OF CORPUS
CALLOSUM
•4 parts
•Anterior end called genu
•Central part is the Trunk
•Posterior bulbous part
called Splenium
•Rostrum is the
prologationfrom the
upper part of the genuto
the upper end of the
lamina terminals

56. FIBERS OF CORPUS
CALLOSUM
•Rostrumconnectsorbital
surfacesoffrontallobe.
•Forcepsminorismadeup
offibersofgenuthat
connectsthe2frontallobes.
•Forcepsmajorismadeupof
fibersofspleniumthat
connectsthe2occipital
lobes.
•Thetapetumformedby
somefibersofthetrunk
andspleniumofcorpus
callosum
FUNCTION OF CORPUS
CALLOSUM
COORDINATES THE ACTIVITIES
OF THE TWO CEREBRAL
HEMISPHERES

57. Diencephalon
•Thediencephalonconsistslargelyofthree
pairedstructures:-thethalamus,
hypothalamus,andepithalamus.
•Thesegraymatterareascollectivelyenclose
thethirdventricle

58. Thalamus
•Thethalamusconsistsofbilateralegg-shapednuclei,
whichformthesuperolateralwallsofthethird
ventricle.
•Thethalamusistherelaystationforinformation
comingintothecerebralcortex.
•Large mass of grey matter, lies immediately lateral to
third ventricle
Two poles
Anterior pole(or end)
Lies behind the interventricularforamen
Posterior pole(or end also called pulvinarlies just
above and lateral to superior colliculus.

59. Two thalami on each side of slit like cavity of 3
rd
ventricle
3 cmslength x 1.5 cmsbreadth Long axis 30
0
oblique to
midline.
Interthalamicadhesion

60. Superior surface
Superior surface
•Thesuperior(dorsal)
surfaceofthethalamus
iscoveredbyathinlayer
ofwhitematter,the
stratumzonale
•Itextendslaterallyand
formstheroofofthe
thirdventricle
•Morelaterallyitforms
partofthefloorofthe
lateralventricle.
•Relatedlaterallyto
caudatenucleus

61. Medial surface
The medial surface
•Themedialsurfaceofthe
thalamusisthesuperior
(dorsal)partofthelateral
wallofthethirdventricle.
•Itisusuallyconnectedtothe
contralateralthalamusbyan
interthalamic adhesion
behindtheinterventricular
foramina.
•Thethalamusiscontinuous
with the midbrain
tegmentum,thesubthalamus
andthehypothalamus

62. Inferior surface of thalamus
•Inferiorsurfaceofthetegmentumisrelated
tohypothalamusanteriorlyandtoventral
thalamusposteriorly.
•Theventralthalamusseperatesthe
thalamusfromtegmentumofmidbrain.

64. Internal structure of the
thalamus
•Thalamusconsistsofmainlyofgreymatter
•Superiorsurfaceiscoveredbyathinlayerofwhite
mattercalledstratumzonale
•Lateralsurfaceiscoveredbyasimilarlayercalled
externalmedullarylayer.
•Internally,thethalamusisdividedintoanterior,medial
andlateralnucleargroupsbyaverticalY-shapedsheet
ofwhitematter,theinternalmedullarylamina
•Nucleioftheanteriorpart.
•Anteriornucleus.
•Nucleiinthemedialpart
•Largestnucleiamongthemmedialdorsalnucleus.

65. Blood supply of thalamus
•Perforatingbranchesoftheposteriorcerebral
artery
•Posteromedialgroup(thalamo-perforating
arteries)supplymedialandanteriorpart.
•Posterolateralgroup(thalamo-geniculate
branches)supply
•posteriorandlateralpartofthalamus.
•Alsorecievesbranchesfromposterior
communicatinganteriorchoroidal,posterior
choroidalandmiddlecerebralartery.

66. Hypothalamus
•Hypothalamus which lies below the thalamus. It
the floor and lower parts of the lateral walls of the
3
rd
ventricle.
•Thehypothalamuscapsthebrainstemandforms
theinferolateralwallsofthethirdventricle.
•Thehypothalamusextendsfromtheopticchiasma
(crossoverpointoftheopticnerves)totheposterior
marginofthemammillarybodies.
•Themammillarybodiespairedpealikenucleithat
bulgeanteriorlyfromthehypothalamus,arerelay
stationsintheolfactorypathways.

67. •The hypothalamus is the main visceral
control center of the body.
•Small in size weighing only4gm, forms only
0.3 % of total brain mass.
•Mainly acts through 3 systems.
a.Autonomous nervous system
b.Endocrine system
c.The limbic system

68. Boundaries
•Anteriory-lamina
terminalis
•Posteriorly-subthalamus
•Inferiorly -structures in
the floor of the 3
rd
ventricle.ie, tuber
cinereum, infundibulam
and mammillary bodies.
•Superiorly –thalamus
•Lateral boundary -
internal capsule.
•Medially-bounded by the
cavity of 3
rd
ventricle.

69. Anteroposteriorlydivided into
•Preopticregion -area adjoining
the lamina terminalis.
•Supra optic region -above the
optic chiasma
•Tubrealregion includes the tuber
cinereum,infundibulamand area
around it.
•Mammillaryregion -includes the
mammillary bodies and area
around it.

70. Hypothalamic nuclei
•Hypothalamus is made up of numerous small nuclear
masses called hypothalamic nucleus.
•They are divided into groups according to their regional
distribution and they differ in their functions also.

71. Thesubthalamicnuclei
•Thesubthalamicnucleiare
smallpairedstructuresthat
are part of the
functionalbasalganglia.
•Theyarelocatedventralto
thethalamus,dorsalto
thesubstantianigraand
medialtotheinternal
capsule.
•Thesubthalamicnucleus
receivesitsmaininputfrom
thelateralpallidum(external
segmentoftheglobus
pallidus). Excitatory,
glutamatergicinputscome
fromthecerebralcortex.

73. Region Nucleus Functions
Preoticregion Preopticnucleus
Contains thesexually
dimorphic nucleus, which
releases GnRH
Supraopticregion
Supra optic nucleus Vassopressinrelease
Anterior nucleusThermo regulation, sweating
Paraventricularnucleus
TRH, CRH Corticotropin&
Oxytocinrelease
Tuberalregion
Arcuate(infundibular
nucleus)
GHRH, feedingand
Dopamine release
Ventromedial nucleus Satiety centre
Dorsomedialnucleus
ControlsBP, HR and GI
stimulation

75. ENDOCRINE CONTROL

76. Autonomic control of body
•Hypothalamuscontrolsautonomicfunctionsofbody
throughsympatheticaswellasparasympathetic
fibresincludingcardiac,andrespiratoryactivity,
vasomotortoneofbloodvessels,digestiveprocess.

77. Part of limbic system
Thelimbicsystemisacomplex
setofstructuresthatliesonboth
sidesofthethalamus,justunder
thecerebrum.Itincludesthe
hypothalamus,thehippocampus,
theamygdala,andseveralother
nearbyareas.Itappearstobe
primarilyresponsibleforour
emotionallife,andhasimp.Role
informationofmemories.

78. Regulation of sleep
•Ventrolateral preopticarea

79. Regulation of Food & water intake
•The extremelateralpart of
theventromedial nucleusof the
hypothalamus is responsible for
the control offoodintake.
Stimulation of this area causes
increased food intake.
Bilaterallesionof this area
causes complete cessation of
food intake.
•

80. Temperature regulation
•The cold and heat sensors
located in the hypothalamus
respond appropriately to
maintain the body
temperature at optimum level
in diverse conditions.
•The ant. Portion of
hypothalamus prevents the
rise in body temperature
while,
•Posterior portion promotes
heat conservation and heat
production.

81. Circadian rhythm
•Hypothalamus regulates the
cyclic activities of the body
,vizsleeping and waking cycle
but itself affected by diurnal
rhythm.
•The circadian rhythm for
many body functions is of
about 24 hours.

82. Sexual dimorphism
•Several hypothalamic nuclei aresexually dimorphici.e.
there are clear differences in both structure and function
between males and females.

83. Other functions
•EMOTIONAL EXPRESSION:_
Hypothalamus regulates the
expression of emotions through
its control over the ANS
(laughting,crying,sweating,cryi
ngetc.)
•Fear processing:_Themedial
zone of hypothalamus is part of
a circuitry that controls
motivated behaviors, like
defensive behaviors.

84. APPLIED ANATOMY
•Lesions in the hypothalamus will cause one of the
following syndromes;
•Obesity
•Diabetes insipidus
•Sexual disturbance
•Disturbance in sleep: somnolence,narcolepsy
•Hyperglycemia and glycosuria
•Diencepahlicautonomic epilepsy : characterized by
flushing,sweating,salivation,lacrimation,tacycardia,r
etardationof respiartoryrate,unconsciousnessetc.

85. Epithalamus
•Themostdorsalportionofthediencephalon
•Theepithalamusformstheroofofthethird
ventricle.Extendingfromitsposteriorborder
andvisibleexternallyisthepinealglandor
body.
•Thepinealglandsecretesthehormone
melatoninand,alongwithhypothalamicnuclei,
helpsregulatethesleep-wakecycle.
•Theposteriorcommissureformsthecaudal
borderoftheepithalamus.

86. The brain stem
•The brain stem regions are
–Midbrain
–Pons
–Medulla oblongata

87. Midbrain
•Connects the ponsand cerebellumwith
the forebrain.
•It is about 0.8 inch in length
•The midbrain is traversed by a narrow
channel called cerebral aqueduct filled with
CSF.

90. AnteriorSurface
Anteriorly,itpresents
twolargebundlesof
fibers,oneoneachside
ofthemidline,called
cruscerebri.
Theoculomotornerve
emergesfromthe
medialaspectofthecrus
ofthesameside
Thecruscerebribounds
theinterpeduncular
fossaoneitherside.

91. Posterior Surface
Posteriorly,themidbrainpresents
fourroundedswellingscalled
colliculi-OneSuperiorand
inferiorcolliculioneoneachside.
Eachcolliculusislaterallyrelatedto
aridgecalledbrachium.
Superiorandinferiorbrachium
arisesfromrespectivecolliculi
Superiorbrachiumconnectsthe
superiorcolliculustolateral
geniculatebody.
Inferiorbrachiumconnectsthe
inferiorcolluculustomedial
geniculatebody
Inthemidlinebelowtheinferior
colliculus,thetrochlearnerve
emergeswhichthenwindsround
thesideofthemidbraintoreachits
ventralaspect.

92. Lateral view

93. Structure of Midbrain
•Themidbraincomprisestwolateralhalvescalledthe
Cerebralpeduncles;
•TheCerebralpedunclesareseparatedintotwopartsbya
pigmentedbandofgraymattercalledsubstantianigra
–Anteriorpart-cruscerebri
–Posteriorpart-tegmentum
Thecentralnarrowcavityiscalledthecerebralaqueduct
oraqueductofSylvius,whichconnectsthe3
rd
and4
th
ventricles.
Thetectumisthepartofthemidbrainposteriortothe
cerebralaqueduct;ithasfoursmallsurfaceswellings
referredtopreviously;thesearetwosuperiorandtwo
inferiorcolliculi.

94. Tectum& Tegmentum

95. Blood Supply
Artery –
•posterior cerebral
artery
•superior cerebellar
artery
•basilar artery
Veins –
•Drained by basal or
great cerebral veins

96. PONS
•Itissituatedanteriorlytothecerebellum
measuringabout1inchinlength.
•Connectsthemedullaoblongatatothe
midbrain.
•Itsalsoconnectstwocerebellar
hemispheresanditsnamecomesfromthis
bridgelikeappearance.

98. Anterior surface of Pons
Ponshasaconvexanteriorsurfacemarkedby
transverselyrunningfiberswhichlaterallyformabundle
calledmiddlecerebellarpeduncle.
MainFeatures:
•Thetrigeminalnerveemergesfromtheanteriorsurfaceat
itsjunctionwithmiddlecerebellarpeduncle.
•Presentsabasilarsulcusinthemidlinewhichlodges
basilarartery
•InthegroovebetweenPonsandthemedullaoblongata,
thereemerge,frommedialtolateral,abducent,facialand
vestibulocochlearnerves.

100. Posterior Surface
•Posteriorsurfacecontains
mediansulcuswhichis
boundedbymedialeminence
onbothsides.
•Inferiorendofmedial
eminenceisslightlyexpanded
toformfacialcolliculus,which
isproducedbyfacialnerve
root.
•Theupperendofsulcus
limitanspresentsabluish-gray
colorationcalledsubstantia
ferruginosa.

101. •Respiratory nuclei:
•Apneustic& pneumotaxiccenters work with
the medulla to maintain respiratory rhythm
•Nuclei & tracts that process and relay info
to/from the cerebellum
•Ascending, descending, and transverse
tracts that interconnect other portions of
the CNS

102. Structure of Pons
PosteriorPart
•Tegmentum
Anteriorpart
•Basispontistraversed
byrunningfibersof
Trapezoidbody.

103. Blood Supply

104. APPLIED ANATOMY
•Unilateral lesions in the lower part of the
ponsresults in paralysis of facial nerve in
the same side and limbs in the opposite side.

105. Medulla Oblangata
•Themedullaoblongata(medulla)isoneof
thethreeregionsthatmakeupthe
brainstem.Itisthemostinferiorofthethree
andiscontinuousabovewiththeponsand
belowwiththespinalcord.Themedulla
housesessentialascendinganddescending
nervetractsaswellasbrainstemnuclei

106. •Relays ascending sensory pathway impulses
from skin and proprioceptors through nuclei
cuneatusand gracilis
–Contains visceral nuclei controlling heart rate,
blood vessel diameter, respiratory rate, vomiting,
coughing, etc.
–Relays sensory information to the cerebellum
through inferior olivarynuclei
–Contains nuclei of cranial nerves VIII–XII
–Contains projection fibers
–Site of decussationof pyramids

108. Structures of the Medulla
Oblongata
•Flankingthemidlineonthemedulla’s
ventralaspectaretwolongitudinalridges
calledpyramids,formedbythelarge
pyramidal(corticospinal)tractsdescending
fromthemotorcortexmostofthesefibers
crossovertotheositesidebefore
continuingintothespinalcord.
•Thiscrossoverpointiscalledthe
decussationofthepyramids

109. •Theolivesareovalswellings.These
swellingsarecausedmainlybythewavy
foldsofgraymatteroftheunderlying
inferiorolivarynuclei.Thesenucleirelay
sensoryinformationonthedegreeof
stretchinmusclesandjointstothe
cerebellum.

110. External Anatomy of the Medulla
•Thesuperiormarginofthemedullaislocatedatthe
junctionbetweenthemedullaandpons
•Theinferiormarginismarkedbytheoriginofthefirstpair
ofcervicalspinalnerves.Thisoccursjustasthemedulla
exitstheskullthroughtheforamenmagnum.
•Lengthisabout3cm,widthisabout2cm
•Surfacesshowsseriesoffissures
–Anteriormedianfissure
–Posteriormedianfissure

111. Anterior median fissure
Pyramid
Anterolateralfissure
Olive

112. Anterior Surface
•There are several structures visible on the anterior surface of
the medulla –namely thethree fissures/sulci, the pyramids, the
olives, and five cranial nerves.
–Anterior median fissure,which is continuous along the
length of the spinal cord. Two sulci are visible –
theventrolateralsulcusand theposterolateralsulcus.
–Thepyramidsare paired swellings found between the
anterior median fissure and the ventrolateralsulcus.
–Theolivesare another pair of swellings locatedlaterally to
the pyramids –between the ventrolateraland posterolateral
sulci.
•Arising from the junction between the pons and medulla is the
abducensnerve (CN VI). Extending out of the ventrolateral
sulcus is the hypoglossal nerve (CN XII). In the posteriolateral
sulcus, three more cranial nerves join the medulla (CN IX, CN X,
and CN XI).

114. Ventral surface of medulla oblongata contains
•Pyramid
•It is an elevation between anterior median and
anterolateral sulcus
•Formed due to decussationof corticospinalfibres.
Pyramid
Olive
Olive
•Oval swelling between anterolateral
posterolateralsulcus,halfan inch
long
•Produced by large mass of gray
matter called inferior olivary
nucleus

115. The posterior surface
•Theposteriorsurfacehasamidlinestructure–
theposteriormediansulcus–whichis
continuousbelowastheposteriormedian
sulcusofthespinalcord.Above,thesulcus
endsatthepointinwhichthefourthventricle
develops.
•Aswemovelateralfromthemidline,
thefasciculusgracilisandfasciculus
cuneatusareseen,separatedbytheposterior
intermediatesulcus.

117. Internal Anatomy of the Medulla
•The internal structures of the medulla must
be viewed in cross section to understand the
layout.Threelevels of the medulla are
typically discussed (inferior –superior):
–Level of decussationof the pyramids
–Level of decussationof the medial lemnisci
–Level of the olives

118. •Themedullacontainsgraymatter,while
the outer portions consist
ofwhitematter.Theposteriorwhitematter
containsthefasiculusgracilisandthe
more lateralfasiculuscuneatus.
Correspondingportionsofgraymatter
extendtotheseregionsandarethenucleus
gracilisandnucleuscuneatusassociated
withatractcalledthemediallemniscus.

120. Functions of the Medulla
Oblongata
•Thesmallsizeofthemedullabeliesitscrucialroleasan
autonomicreflexcenterinvolvedinmaintainingbody
homeostasis.Themedullacontainstheseimportant
functionalgroupsofvisceralmotornuclei:
Cardiovascularcenter.Adjuststheforceandrateofheart
contractiontomeetthebody’sneeds,andthevasomotor
center,whichchangesbloodvesseldiametertoregulate
bloodpressure.
Respiratorycenters.Thesegeneratetherespiratory
rhythmandcontroltherateanddepthofbreathing.
Variousothercenters.Additionalcentersregulatesuch
activitiesasvomiting,hiccuping,swallowing,coughing,and
sneezing

121. The Limbic System
•The limbic system is a group of structures
located on the medial aspect of each
cerebral hemisphere and diencephalon.
•These functional system:
–Includes cerebral and diencephalon structures
(e.g., hypothalamus and anterior thalamic
nuclei)
–Mediates emotional response
–Involved in memory processing

123. •The limbic system is our emotional, or affective
(feelings), brain.
•Amygdaloidbody is critical for responding to
perceived threats such as angry or fearful facial
expressions with fear or aggression.
•The cingulate gyrusplays a role in expressing
our emotions through gestures and in resolving
mental conflicts when we are frustrated.
•Rhinencephalonhelps the brain in responds to
odors.

124. Reticular Formation
•Thereticularformationisa
setofinterconnectednuclei
thatarelocatedthroughout
thebrainstem.Thereticular
formationisnotanatomically
welldefinedbecauseit
includesneuronslocatedin
diversepartsofthebrain.
•A functional system:
–Maintains cerebral cortical
alertness (reticular activating
system)
–Filters out repetitive stimuli
–Helps regulate skeletal and
visceral muscle activity

125. Reticular Activating System
•Theneuronsofthepartofthereticular
formationknownasthereticularactivating
system(RAS).
•Reticularactivatingsystemsenda
continuousstreamofimpulsestothecerebral
cortex,keepingthecortexalertandconscious
andenhancingitsexcitability.Impulsesfromall
thegreatascendingsensorytractssynapse
withRASneurons,keepingthemactiveand
enhancingtheirarousingeffectonthe
cerebrum.

126. •The reticular formation is divided into three
columns:
–Raphenuclei(median),
–Magnocellularred nucleus(medial zone),
–Parvocellularreticular nucleus(lateral zone).

127. •Theraphenucleiistheplaceofsynthesisof
theneurotransmitterserotonin,whichplays
animportantroleinmoodregulation.
•Themagnocellularrednucleusisinvolvedin
motorcoordination.
•The parvocellularnucleus
regulatesexhalation.

128. THANK YOU