Learning Objectives
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A Different lobes and surfaces of Cerebral hemisphereB. Blood supply of different regions of cerebral hemisphere
C Important sulci and gyri
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D Different functional areas located in cerebral hemisphere
E. Lesions and its effects
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2Cerebrum
Largest part of the brain
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Heavily convoluted bilobed
structure
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4
Cerebral hemispheres
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General Appearance:Separated by a deep midline sagittal
fissure ? longitudinal cerebral fissure
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In the depth of the fissure, the corpuscal osum connects the hemispheres
across the midline
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Gyri ? the folds of the surface of
hemispheres
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Sulci ? the fissures separate the gyri5
Surfaces of Cerebral Hemisphere
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Three surfaces:
Superolateral surface
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Inferior surfaceMedial surface
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Borders1 Superomedial border
2 Superciliary border and inferolateral border
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(Shows preoccipital notch)
3. Medial orbital border, hippocampal border or
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inferomedial border and medial occipital border6
Lobes of Cerebral Hemispheres
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Cerebral hemispheres are divided into
lobes by the central, parieto-occipital,
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lateral and calcarine sulciLobes are named according to the
cranial bones under which they lie
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Lobes are:
Frontal
Parietal
Temporal
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Occipital8
Cerebral hemisphere
? the essential features can be
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1
summarized by stating that:-
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1. the frontal lobe lies in front ofthe central sulcus (1) and above
2
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the lateral sulcus (2) .
3
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2. the parietal lobe is behind thecentral sulcus and above the
lateral sulcus.
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3. the temporal lobe is below the
lateral sulcus
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4. the occipital lobe lies below andP
behind the parieto-occipital
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F
sulcus (3) .
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OT
Main sulci
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1
1. Central sulcus
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32. Lateral sulcus
3. Parito-occipital sulcus
4. Calcarine sulcus
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2
5. Cingulate sulcus
6. Cal sosal sulcus ( Sulcus
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of corpus cal osum )
7. Orbital sulcus
8. Parahippocampal sulcus
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9. Col ateral sulcus5
10. Occipiti-temporal sulcus
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6
- First (6) can be seen in
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sagittal sections- Last 4 seen only in axial
4
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sections
Main sulci
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71. Central sulcus
2. Lateral sulcus
3. Parito-occipital
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sulcus
4. Calcarine sulcus
5. Cingulate sulcus
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6. Cal sosal sulcus (Sulcus of corpus
10
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8
cal osum )
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97. Orbital sulcus
8. Parahippocampal
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sulcus9. Col ateral sulcus
10. Occipiti-temporal
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sulcus1. Central sulcus 2. Lateral sulcus 3. Parito-occipital sulcus
4. Calcarine sulcus
5. Cingulate sulcus
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6. Cal sosal sulcus ( Sulcus of corpus cal osum )
1
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35 6
2
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4
2
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2. Parahippocampal sulcus3. Col ateral sulcus
4. Occipiti-temporal sulcus
3
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4
Main gyri
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12
1. Precentral
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3
2. Postcentral
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34
3. Frontal (superior, middle & inferior)
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3
4. Parietal (superior & inferior) 5-
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55. Temporal (superior, middle &
inferior)
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5
6. Cal osal
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57. Medial frontal
8. Paracentral lobule
9. Precuneus
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7
8
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10. Cuneus6
11. Lingual gyrus
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9
12. Orbital gyri
13. Gyrus rectus
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10
14. Parahippocampal
15. Occipitotemporal (medial & lateral)
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11
16. Uncus
Main gyri
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13
1. Precentral
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2. Postcentral12
3. Frontal (superior, middle & inferior)
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4. Parietal (superior & inferior) 5-
5. Temporal (superior, middle &
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inferior)6. Cal osal
16
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7. Medial frontal
8. Paracentral lobule
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1515
9. Precuneus
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14
10. Cuneus
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11. Lingual gyrus12. Orbital gyri
13. Gyrus rectus
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14. Parahippocampal
15. Occipitotemporal (medial & lateral)
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16. Uncus1
1. Rectus gyrus
2. Uncus ( parahippocampus
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gyrus )
2
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3. Hippocampal gyrus3
9
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Main sulci
Central sulcus
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Indents the superior medial border of thehemisphere, 1 cm behind the mid-point
It runs downward, forward and toward the
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lateral sulcus across the lateral aspect of the
hemisphere
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The central sulcus is the only sulcus thatindents the superior medial border
-
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10
Main sulci (Cont'd)
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Lateral sulcusDeep cleft on the inferior and lateral
surfaces of the cerebral hemisphere
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It consists of a short stem and three rami
- Anterior horizontal , anterior
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ascending and posterior11
Main sulci (Cont'd)
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Parieto-occipital sulcus:
Begins on the superior medial border of
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the hemisphere, about 5 cm anterior tothe occipital pole
It passes downward and anteriorly on the
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medial surface to meet the calcarine
sulcus
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Main sulci (Cont'd)
Calcarine Sulcus- Medial surface
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Insula/Island Of Reil? portion of the cerebral cortex
folded deep within the lateral
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sulcus.? Play a role in consciousness and
emotions
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? The cortical area overlying the
insula toward the lateral surface of
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the brain is the operculum(meaning lid).
? The opercula are formed from
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parts of the enclosing frontal,
temporal, and parietal lobes.
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? Insulaa is surrounded by circularsulcus ( arrow !! )
Superior surface
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of temporal
operculum
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presentsanterior and
posterior
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transverse
temporal gyri
Other Sulci and Gyri
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Superolateral su12rface
Frontal lobe ? anterior to central sulcus
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and superior to lateral sulcusSuperolateral surface of frontal lobe is
divided by three sulci into four gyri
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Precentral sulcus and gyrus
Superior and inferior frontal sulci
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Superior, middle and inferior frontal gyriAnterior and ascending rami of lateral
sulcus divide inferior frontal gyrus into
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PARS ORBITALIS, PARS TRIANGULARIS PARS
OPERCULARIS
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1315
Superolateral surface
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Parietal lobe ? POST
CENTRAL SULCUS AND
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GYRUSo INTRAPARIETAL SULCUS
AND SUPERIOR AND
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INFERIOR PARIETAL LOBULE
Lateral
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sulcusSuperolateral surface
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o PARIETAL LOBE-Few sulci extend into inferiorparietal lobule and divided into
o SUPRAMARGINAL GYRUS AROUND LATERAL
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SULCUS
o ANGULAR GYRUS AROUND SUPERIOR
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TEMPORAL SULCUSo ARCUS TEMPORO-OCCIPITALIS AROUND
INFERIOR TEMPORAL SULCUS
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14
Superolateral surface
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Temporal lobe ? inferior to lateral sulcusTwo sulci ? SUPERIOR AND INFERIOR
SULCUS
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Three gyri- SUPERIOR, MIDDLE AND
INFERIOR TEMPORAL GYRI
Superior surface of temporal operculum
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(Superior temporal gyrus)presents anterior and
posterior transverse temporal gyri. Anterior
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gyrus forming primary auditory area, also calledHESCHL'S GYRUS
Superolateral surface
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Occipital lobe ? small area behind theparieto-occipital sulcus
LATERAL OCCIPITAL SULCUS
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LUNATE SULCUSTRANSVERSE OCCIPITAL SULCUS
MEDIAL SURFACE
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CINGULATE SULCUS AND CINGULATE GYRUS
CALLOSAL SULCUS
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PARACENTRAL LOBULE(CORTICAL CENTRE OFMICTURATION AND DEFECATION) AND MEDIAL FRONTAL
GYRUS
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CALCARINE SULCUS AND PARIETO-OCCIPITAL SULCUS
SUPRASPLENIAL SULCUS IN PRECUNEUS
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INFERIOR SURFACEORBITAL SURFACE- OLFACTORY SULCUS, GYRUS RECTUS
ORBITAL SULCUS AND ORBITAL GYRI
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TENTORIAL SURFACE- MEDIAL COLLATERAL SULCUS AND LATERAL OCCIPITO-TEMPORAL
SULCUS
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LINGUAL GYRUS ? BETWEEN COLLATERAL SULCUS AND CALCARINE SULCUSLINGUAL GYRUS ANTERIORLY CONTINUE WITH PARAHIPPOCAMPAL GYRUS WHOSE
ANTERIOR END HOOK LIKE LIMITED BY RHINAL SULCUS- UNCUS
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MEDIAL AND LATERAL OCCIPITO- TEMPORAL GYRUS
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BLOOD SUPPLY- SUPEROLATERALSURFACE
MIDDLE CEREBRAL ARTERY EXCEPT
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STRIP ALONG SUPEROMEDIAL BORDER FROM FRONTAL
POLE TO PARIETO OCCIPITAL SULCUS BY ACA
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OCCIPITAL LOBE AND INFERIOF TEMPORAL GYRUSEXCLUDING TEMPORAL POLE BY PCA
BLOOD SUPPLY- INFERIOR
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SURFACE
ACA- MEDIAL PART OF ORBITAL SURFACE
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MCA-LATERAL PART OF ORBITAL SURFACE ANDTEMPORAL POLE
PCA- TENTORIAL SURFACE
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BROADMANS AREAS AND
FUNCTIONAL AREAS OF CEREBRAL
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HEMISPHERESpecific
Sulci/Fissures:
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Central Sulcus
Longitudinal
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FissureSylvian/Latera
l Fissure
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Transverse Fissure
http://www.bioon.com/book/biology/whole/image/1/1
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http://www.dalbsoutss.eq.edu.au/Sheepbrains_Me/human_braFrontal Lobe - Cortical Regions
Primary Motor Cortex
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/Brodmann,s area 4Precentral Gyrus ? it cntro
ls
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all voluntary movements of
the contralateral side of the
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bodySite where movements of
the various parts of the
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body are initiated
Recieves sensory input fro m
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cerebellum and thalamus
The body is represented
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upside down along the
precentral gyrus
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Investigation (Phineas Gage)Primary Motor
Cortex/ Precentral
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Gyrus
Broca's Area
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OrbitofrontalCortex
Olfactory Bulb
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Regions
Modified from:
secondary motor area/6,8,44 and 45
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Precentral gyrus,sup,middle,inf frontal gyriIt programs the activity of the PMA
Stronger stimulation is required to produce
the same degree of movement
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Broca's Area ?44,45
Inf.frontal gyrus
Brings about the formation of words.
Located on Left Frontal Lobe
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Broca's Aphasia ? Results in the ability tocomprehend speech, but the decreased
motor ability (or inability) to speak and
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form words
Frontal eye field 8,
Middle frontal gyrus
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Voluntary eye movements towardsopposite side and the
accomodation pathway
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also controls eyelid movements
Prefrontal cortex9,10,11,12
Concerned with the makeup of the
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individual,s personality
Head rotation area
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Parietal Lobe - Cortical RegionsPrimary sensorymotor Cortex
1,2,3(Postcentral Gyrus) ? Site involved with
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processing of tactile and proprioceptive
information.
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?Somatosensory Association Cortex -5,7 supparietal assists with the integration and
interpretation of sensations.
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?Primary Gustatory Cortex 43
?Inferior part of the post central gyrus? Primary site
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involved with the interpretation of the sensation ofTaste.
Primary
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SomatosensoryCortex/ Postcentral
Gyrus
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Somatosensory
Association Cortex
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Primary GustatoryCortex
Modified from:
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http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Regions
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Occipital Lobe ? CorticalRegions
Primary Visual Cortex ? This is the primary area of
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the brain responsible for Vision
?Visual Association Area ? Interprets
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information acquired through theprimary visual cortex.
Primary Visual
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Cortex
Visual Association
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AreaModified from:
http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
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Regions
Temporal Lobe ? Cortical
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RegionsPrimary Auditory Cortex ?41,42 mostly
hidden in the lateral sulcus
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Responsible for hearing
Its anterior part recieves low freq sounds
Post part ?high freq sounds
Sec. Auditory Cortex 22
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Interpretation of soundsTemporal Lobe ? Cortical
Regions
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?Primary Olfactory Cortex ? sense of smel(Not visible on the superficial cortex)
?Wernicke's Area superior and middle
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temporal gyri
?Understanding of speech
- Wernicke's Aphasia ? Words and sentences are
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not clearly understood, and sentence formation
may be inhibited.
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Primary AuditoryCortex
Wernike's Area
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Primary Olfactory
Cortex (Deep)
Conducted from Olfactory
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Bulb
Modified from:
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Regionshttp://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
dominant hemisphere
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95-left
Broca
90% right handed
BLOOD SUPPLY
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Anterior and middle cerebral artery
(internal carotid artery)
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Posterior cerebral artery (basilar artery)Physiological information about brain
? Left hemisphere is dominant in Which hemisphere
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90% of the right handed and 64%
is dominant ?!
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of the left handed? Righ hemisphere is dominant in
10% of righ handed and 20% of
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left handed
? In the remaining 16% of left
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handed both hemispheres aredominant .
? Speech areas in brain usual y in
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the dominant hemisphere !! ( OF
CLINICAL IMPORTANT )
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Brodmann areasMotor areas of cortex
? 1- primary motor area :-
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- MSI area ( precentral gyrus )
MSI
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- MSI area ( Anterior part ofMSI
paracentral lobule )
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? 2- secondary motor area
? Posterior parts of frontal
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gyri extending medial yPrimary motor area
? Broadmann area 4
? The area Msl is where movements
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of the various parts of the body
are initiated,
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MSI? Afferent :- receives its main inputs
MSI
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from
the
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cerebel umand
thalamus.
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? Efferent :- the corticonuclear and
corticospinal (pyramidal) tracts.
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? MSI area receives many fibresfrom the basal nuclei and is
concerned
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with
postural
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mechanisms, but this area is notyet clearly understood.
Motor homunculus
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? the body is represented upside
down along this cortex, although
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the face itself is represented theright way up.
? The face lies lowest, then the
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hand (a very large area), then arm,
trunk and leg.
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? The leg and perineum areasoverlap the superior border and
extend down on the medial
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surface of the hemisphere
? Blood supply :-
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? 1- middle cerebral artery? 2- anterior cerebral a. ( leg area )
Primary motor area
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? Lesions to this area produce
contralateral paralysis !!
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? Organs that supplied bilateral yare the less affected ...
? CNs are supplied bilateral y ?!!
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Secondary motor area
? Or supplementary motor area
? Broadmann are 6
? Location :- Posterior parts of
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frontal gyri extending medial y
? The function of the secondary
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motor area:? 1- To store programs of motor
activity
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resulted
from
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pastexperience
? 2-
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Controls
sequence
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ofmovements
? 3- Controls spatial & postural
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orientation movements.
? 4- Controls bimanual movements.
? Blood supply: Middle & anterior
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cerebral arteries
secondary motor area
? Lesions :-
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? Apraxia (inability to execute learned purposeful movements despitehaving the desire and the physical capacity to perform them).
? There is no or little loss of strength
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Boca's area
? The motor (anterior) speech area
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(of Broca, areas 44 and 45) isusual y situated in the inferior
frontal gyrus on the left side (in
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right-handed and in most left-
handed people), below and in
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front of the face area and centredon the pars triangularis between
the anterior and ascending rami of
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the lateral fissure.
? Damage to it produces motor
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aphasia -- difficulty in finding theright words, but not paralysis of
laryngeal musculature.
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? Blood supply :-
? Middle cerebral a.
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Wernicke's area? The posterior speech area (of
Wernicke) is in the posterior parts of
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the superior and middle temporal gyri
and extends into the lower part of the
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parietal lobe.- It is connected to the Broca's, visual &
auditory cortex
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? Function:
? To understand the written and spoken
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language? Its integrity is necessary for the
understanding of speech.
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? Lesion ... Receptive dysphasia; the
patient responds by intact, but
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irrelevant speech!? Blood supply:
? Middle cerebral artery
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Prefrontal cortex
? The prefrontal cortex is an
extensive area that lies anterior to
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the precentral
? The prefrontal area is concerned
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with1. the makeup of the individual's
personality.
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2. regulator of the person's depth of
feeling.
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3. It also exerts its influence indetermining the initiative and
judgment of an individual.
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Prefrontal cortex? Lesions :-
? It is now general y agreed that
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destruction of the prefrontal
? region does not produce any
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marked loss of intelligence? Tumour or traumatic destruction
of the prefrontal cortex result in
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the person's losing initiative and
judgment.
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? Emotional changes that occurinclude a tendency to euphoria.
? The patient no longer conforms to
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the accepted mode of social
behavior and becomes careless of
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dress and appearance.? Bipolar disorders
? Schizophrenia
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Sensory areas
? 1- Primary somatosensory area
- The postcentral gyrus
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1
- Posterior part of l p
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o ab r
u alce
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e ntral
2
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- Recieves primary from thalamus- Sensations from the oral region,
pharynx, larynx & perineum are
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received bilateral y? 2- Secondary ( or association )
somatosensory area.
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- Occupies the superior parietal
lobule
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Primary sensory area? Sensory homunculus:
? The amount of the cortex for a
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particular part of the bod isrelated
to
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its
functional
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importance&
number
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of
receptors ( not to its size)
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? Blood supply:- Middle cerebral artery
- Anterior cerebral artery (leg area)
Primary sensory area
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? Lesions :-
? Lesions
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ofthe
primary
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somesthetic area of the cortex
result in contralateral sensory
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disturbances, which are mostsevere in the distal parts of the
limbs. Crude painful, tactile,and
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thermal stimuli often return,but
this is believed to be due to the
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function of the thalamus.? The patient remains unable to
judge
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? degrees of warmth, unable to
localize tactile stimuli accurately,
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and unable to judge weights ofobjects.
? Loss of muscle tone may also be a
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symptom of lesions of the sensory
cortex.
Secondary somatosensory area
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? Function:- Receive different sensory
modalities & relate them to past
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experience. e.g; object recognitionwithout vision.
- Lesions = asterognosis !!
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- Inable to identify things withoutsee them ...
Primary visual cortex
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? Broadmann area 17? Functions:
- Receives fibers from the opposite
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field of vision- It also excludes & modulates
unwanted images!
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? Blood supply:
- Posterior cerebral artery
? Lesions :-
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? Crossed homonymous hemianopiaSecondary visual cortex
? Brodmann area 18,19
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? Surrounded by the primary visual
cortex ...
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? Functions to relate the visualinformation to past experiences
? Lesions produce ... Visual agnosia;
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loss of ability to recognize objects
seen in the opposite field of vision
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WHY don't we see everything upside-down?? -Brain makes images 'easier' to see by:
? 1- Combining the two images of the two eyes (in corpus cal osum).
? 2- Make images right-side-up (in the visual cortex).
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? It does this because your brain is so USED to see things upside-down thatit eventual y adjusts to it (it's easier to flip the image than to try using
hands and legs with an upside-down world)
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? For the first days, babies see everything upside-down!
Primary auditory area
? Broadmann area 41,42
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? In the inferior wal of lateral sulcus
? Afferent: Principal y from the
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medial geniculate body? Blood supply:
- Middle cerebral artery
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- Lesions
produce ...
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Partialdeafness in both ears with
inability to locate sound.
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- The greater loss being in the
opposite ear
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- (cochlear nuclei send 2nd order tothe olivary nucleus & nuclei of
trapezoid body bilateral y)
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Auditory pathway
? Explaning why greter loss of
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inability to hear on theopposite site !!!
? Cochlear n. send fibers more
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to the other side than the
same side ...
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Secondary auditory area? Broadmann area 22
? Lies posterior to the primary
auditory area
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? Function:
- To interpret sounds and associate
the auditory input with other
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sensory information.
? Blood supply:
? Middle cerebral artery
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? Lesions : auditory agnosia !!
The dominant angular gyrus
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? This part is often considered apart of the Wernicke area
? Lesion here results in inability to
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read (alexia) or write (agraphia).
Aphasia
Sensory aphasia
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Alexia
Agraphia
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Motor aphasiaA lesion resulting in a nonfluent expressive
aphasia would most likely be found in the
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(A) temporal lobe
(B) parietal lobe
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(C) frontal lobe(D) occipital lobe
Alexia without agraphia and aphasia would
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most likely result from occlusion of the
(A) left anterior cerebral artery
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(B) right anterior cerebral artery(C) left middle cerebral artery
(D) left posterior cerebral artery
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(E) right posterior cerebral artery
A patient is asked to bisect a horizontal line
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through the middle, to draw the face of a clock,and to copy a cross. The patient bisected the
horizontal line to the left of the midline,
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placed all of the numerals of the clock on the
right side, and did not complete the cross on
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the left side. The most likely lesion site for thisdeficit is the
(A) left frontal lobe
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(B) right parietal lobe
(C) left parietal lobe
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(D) right temporal lobe(E) left occipital lobe
Arterial supply to Brain
? Tissue of the brain ( paranchyme )
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al is supplied by two sources ...
? 1- branches of internal carotid
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1ACA
MCA
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artery
? 2- branched of basilar artery
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2ECA
ICA
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PCA
Basialr a.
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CCAVertebral a.
Vertebral a.
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aorta
Subcalvain a.
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Subcalvain a.Branches of the vertebral a.
1. Posterior
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inferior
cerebel ar a.
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2. Anterior spinal a.2
1
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Branches of the basilar a.
1. Anterior inferior cerebel ar a.
2. Superior cerebel ar a.
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3. Posterior cerebral a.32
1
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Blood supply to Brain
Anterior cerebral artery
? leaves the internal carotid artery
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and passes forwards above the
optic nerve
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? It is connected to its fellow of theopposite side by the anterior
communicating artery. It is
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distributed to the orbital surface of
the frontal lobe and to the whole
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of the medial surface of thehemisphere above the corpus
cal osum as far back as the parieto-
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occipital sulcus
Anterior cerebral artery
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? The motor and sensory areas for the opposite leg, foot and perineum,including the micturition and defecation centres, lie in its territory.
? Because of the anastomosis via the anterior communicating artery, it is
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usual y possible for one anterior cerebral to be supplied with blood from
the contralateral internal carotid.
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Anterior cerebral a. syndrome1. Hemiparesis or hemiplegia contralateral y, involving primarily the lower
limbs and pelvic floor musculature
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2. Sensory deficits contralateral y, involving primarily the leg and perineum3. Apraxia (due to branches to the supplementary motor area and corpus
cal osum)
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4. Disconnection syndrome (due to cal osal branches)5. Anosmia (due to branches of the olfactory bulb and olfactory tract)
6. Urinary incontinence
7. Grasp reflex and or sucking reflex contralateral y (if circle of Wil is
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compromised)Middle cerebral artery
? The middle cerebral artery is
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the largest and most directbranch of the internal carotid
and therefore most subject to
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embolism.
? It passes deep into the lateral
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sulcus to supply the cortex ofthe insula and overlying
opercula.
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? It reaches the lateral surface of
the hemisphere
Middle cerebral artery
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? by continuing in the lateral
sulcus, from which its branches
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emerge and ramify over an areathat fal s short of the borders of
the lateral surface by one gyrus
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or its equivalent breadth.
?
? In its area of cortical
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distribution lie the motor and
sensory areas for the opposite
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half of the body, excluding leg,foot and perineum (which are in
anterior cerebral territory), and
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the auditory and speech areas.
Middle cerebral a. syndrome
1. Hemiparesis or hemiplegia of the lower half of the contralateral face
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2. Hemiparesis or hemiplegia of the contralateral upper and lowerextremities
3. Sensory loss of the contralateral face, arm and leg
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4. Ataxia of contralateral extremities5. Speech impairments/aphasia: Broca's area, Wernicke's or Global aphasia
as a result of a dominant hemisphere lesion (usual y the left brain)
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6. Perceptual deficits: hemispatial neglect, anosognosia, apraxia, andspatial disorganization as a result of a non-dominant hemisphere lesion
(usual y the right brain)
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7. Visual disorders: d?viation conjugu?e, a gaze preference towards the side
of the lesion; contralateral homonymous hemianopsia
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Note: *faciobrachial deficits greater than that of the lower limbPosterior cerebral artery
? The posterior cerebral artery
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curls back around the cerebralpeduncle supplying it and the
optic tract, and passes back
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above the tentorium to supply
the inferomedial surface of the
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temporal and occipital lobes? Its territory meets that of the
anterior cerebral artery at the
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parieto-occipital sulcus.
Its
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branches extend around theborders of the brain to supply
the inferior temporal gyrus and
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a corresponding strip of cortex
on the lateral surface of the
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occipital lobe. .Posterior cerebral artery
? The visual area for the
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opposite field of vision lies
whol y within its territory,
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but the middle cerebralbranches can sometimes
extend sufficiently far back
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on the occipital lobe to
supply the macular part of
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the visual area .? Thus the macular field of
vision may be spared when
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the rest of the visual area is
destroyed by a posterior
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cerebral thrombosis.Posterior cerebral a. syndrome
1. Visual disorder : Contralateral homonymous hemianopsia & cortical
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blindness with bilateral involvement of the occipital lobe branches
2. visual agnosia
3. dyslexia, Anomic aphasia, color naming and discrimination problems
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4. memory defect5. involuntary movements: chorea, intention tremor, hemibal ismus
6. contralateral hemiplegia
7. Weber's syndrome: occulomotor nerve palsy
8. B?lint's syndrome: loss of voluntary eye movements optic ataxia,
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asimultagnosia (inability to understand visual objects).
Circle of wil is
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? 1, Internal carotid artery.? 2, Posterior cerebral
artery.
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8
? 3, Anterior cerebral
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artery.? 4, Anterior cerebral
artery.
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? 5, Middle cerebral artery.
? 6, Basilar artery.
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? 7, Vertebral artery.? 8, anterior
communicating artery .
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