Download 15-CEREBRUM

By Prof.
Saeed Abuel Makarem
• It is the largest part of the
forebrain.
• It is highly developed in
human.
• It is derived from the
telencephalon.
• The 2 cerebral hemisphere
are incompletely separated by
the median or greater
longitudinal fissure.
• They are connected by the
corpus callosum.
• Each hemisphere has a cavity
called the lateral ventricle.
CEREBRUM
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Each hemisphere has
3 surfaces,
3 poles,
4 borders,
4 Lobes.
Surfaces:
• Lateral or superolateral:
Convex and related to the
skull vault.
• Medial:
• Flat & vertical and related
to the falx cerebri &
median longitudinal
fissure.
• Inferior:
• Divided into orbital and
tentorial parts by the stem
of lateral sulcus.
CEREBRUM : SURFACES
• Four borders:
• 1- Medial or
Superomedial border:
Between lateral &
medial surfaces.
• 2- Inferolateral border:
Between lateral &
inferior surfaces.
• Its anterior part may
be called superciliary
border.
• 3- Medial orbital
border.
• 4- Medial occipital
border.
CEREBRUM: BORDERS
CEREBRUM
3 POLES & 4 LOBES
• Each hemisphere has 3
poles:
• 1- Frontal pole.
• 2- Occipital pole.
• 3- Temporal pole.
• Also, each hemisphere has 4
lobes:
• 1- Frontal lobe.
• 2- Temporal lobe
• 3- Parietal lobe.
• 4- Occipital lobe.
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Lateral sulcus or fissure:
Separates the frontal and parietal
lobes from the temporal lobe.
Central sulcus:
Begins from the superomedial border
½ inch behind the midpoint between
the frontal and occipital poles.
It descends downward & forward
making an angle about 70▫ with the
vertical line.
It stops slightly above the lateral
sulcus.
Pre-central: a finger breadth anterior
& parallel to the central sulcus.
Post-central: a finger breadth behind
& parallel to the central sulcus.
Superior & inferior frontal sulci
Superior & inferior temporal sulci.
Interparietal sulcus.
Lunate sulcus
SULCI
ON THE LATERAL SURFACE
• Pre-central gyrus:
Between central &
precentral sulci.
• Postcentral gyrus :
• Between central &
post-central sulci.
• Superior, middle &
inferior frontal gyri.
• Superior, middle &
inferior temporal gyri.
• Superior & inferior
parietal lobules.
• Angular gyrus
GYRI
ON THE LATERAL SURFACE
• Callosal sulcus: just above the
corpus callosum.
• Cingulate sulcus: one inch
above & parallel to the callosal
sulcus.
• Parieto-occipital sulcus: begins
in the upper border 4 cm in
front of the occipital pole
• It ends at the meeting of
calcarine & postcalcarine sulci.
• Calcarine:
• Begins below the splenium then
passes backwards and upwards
to meet the parieto-ocipital
sulcus then continuous as the
postcalcarine sulcus.
• Postcalcarine sulcus: It is an
extension of the calcarine.
SULCI
ON THE MEDIAL SURFACE
• Cingulate gyrus:
Between the callosal
& cingulate sulci.
• Paracentral lobule:
• It is the continuation
of the precentral &
postcentral gyri.
• Precuneus: behind
the paracentral
lobule.
• Cuneus: between the
parieto-ocipital &
postcalcarine sulci.
GYRI
ON THE MEDIAL SURFACE
• Olfactory sulcus:
• Close & parallel to the medial
orbital margin.
• Orbital sulcus:
• Irregular H- shaped lateral to
olfactory sulcus.
• Stem of lateral sulcus:
• It divides the inferior Surface
into, orbital & tentorial parts.
• Rhinal sulcus:
• A short sulcus on the
temporal pole.
• Collateral sulcus:
• Behind the rhinal sulcus and
extends to the occipital pole.
• Occipitotemporal sulcus:
• Lateral to the collateral sulcus
• It extends from temporal to
occipital poles..
SULCI
ON THE INFERIOR SURFACE
• Gyrus rectus:
• Medial to the olfactory sulcus.
• Orbital gyri;
• Anterior, posterior, medial and
lateral, orbital gyri.
• Lateral occipitotemporal gyrus:
Lateral to occipitotemporal
sulcus.
• Medial occipitotemporal gyrus:
Medial to occipitotemporal
sulcus.
• Parahippocampal gyrus:
• Medial to collateral sulcus.
• Lingual gyrus:
• Between collateral & calcarine
sulci.
• Uncus: Anterior end of the
Parahippocampal gyrus
• It is the smell center.
GYRI
ON THE INFERIOR SURFACE
IMPORTANT CENTERS OF THE
CEREBRAL CORTEX
OR
MAIN FUNCTIONAL AREAS
OF THE CEREBRAL CORTEX
The cerebral cortex is
important for:
Conscious awareness ,
Though,
Memory and
Intellect.
Most sensory modalities
ascend to the cortex
from the thalamus,
perceived & interpreted
in the light of the
previous experience.
Posterior part of
the cerebrum
receives sensory
information in:
1- Parietal lobe
(Somatosensory),
2- Occipital lobe
(Vision),
3- Temporal lobe
(Hearing).
• Information is
elaborated to the
association cortex,
( at the meeting of the
parietal, temporal &
occipital) for
identification by
touch, sight &
hearing.
• The limbic system
(medial part of
cerebrum) enable
storage & retrieval of
the information
processed in the
posterior cortex.
Storage & Retrieval of
information
• The frontal lobe
(anterior part of
cerebrum) is
concerned with
• the organization of
movement:
• 1-Primary motor
area.
• 2-Premotor area.
• 3-Supplementary
motor area.
• 4- Prefrontal area
(guidance of
complex motor
behaviour).
MOTOR AREA
• In precentral gyrus & anterior
part of the paracentral lobule.
• It corresponds to
Brodmann’s area 4 .
• Body is represented upside down.
• Size of the functional area is
directly proportional to the
skilled movement, not to the size
of the muscle.
• It is here that actions are
conceived and initiated.
• The principal subcortical afferent
to PMC is from Lateral ventral
nucleus (LVN) of thalamus.
• LVN receives its input from
globus pallidus & dentate
nucleus.
PRIMARY MOTOR CORTEX
(PMC)
• Lesion: Upper 1/3 and paracentral lobule leads to affection of
voluntary control in lower limb & perineum of the opposite side.
• Lower 2/3rds: affection of voluntary control of the head, neck & upper
limb on the opposite side.
• Isolated lesion of the premotor cortex leads to apraxia.
• (Inability to perform skilled complex voluntary movement in spite of
absence of muscle paralysis)
• Lies anterior to primary
motor cortex.
• Brodmann’s area 6.
• It includes the posterior
parts of superior, middle
& inferior frontal gyri.
• Function:
• Programming &
preparing for movement
and control of posture.
• It receives its afferent
from ventral anterior
nucleus of thalamus.
PREMOTOR CORTEX
6
• On the medial surface of
the premotor cortex.
• The principle subcortical
input to premotor and
supplementary motor
cortex is the ventral
anterior nucleus of the
thalamus.
• This nucleus receives its
afferent from the globus
pallidus & substantia
nigra
SUPPLEMENTARY MOTOR
CORTEX
• It lies in posterior part
of the middle fontal
gyrus.
• It is corresponding to;
• Brodmann's area 8
• It controls conjugate
movement of the eye.
• Unilateral damage to
area 8 causes conjugate
deviation of the eyes to
the side of the lesion.
FRONTAL EYE FIELD
• In the inferior frontal gyrus
in the dominant (usually left)
hemisphere.
• Brodmann’s areas 44 & 45
• It has connections with
ipsilateral temporal, parietal,
occipital lobes that share in
language function.
• Lesion:
• (Left middle cerebral artery)
• Expressive or motor aphasia
(inability to express thought,
answer or writing inspite of
a normal comprehension)
MOTOR SPEECH AREA
BROCA’S AREA
• Lies anterior to
premotor area.
• It has rich connections
with parietal, temporal
and occipital cortex.
• Functions:
• Intellect.
• Judgment.
• Prediction.
• Motivation
• Planning of behaviour.
PREFRONTAL CORTEX
• In the postcentral gyrus &
posterior part of paracentral
lobule.
• It correspond to Brodmann’s
areas 1, 2 and 3).
• Here thalamocortical neurons
terminate (3rd order neuron).
• Input comes from ventral
posterior nucleus (VPN) of the
thalamus.
• Within the somatosensory
cortex the contralateral half of
body is represented upside
down.
PRIMARY SOMATOSENSORY
CORTEX
• VPN receives:
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1-Medial lemniscus
(Fine touch & proprioception).
2-Spinal lemniscus
(coarse touch & pressure).
3-Spiothalamic tract
(pain & temperature).
4- Trigeminothalamic tract
(general sensation from head)
• Lies in the superior bank of the
middle of the superior
temporal gyrus.
• Hidden within the lateral
fissure.
• Brodmann's 41, 42.
• Its precise location is marked
by small transverse temporal
gyri ( Heschl’s convolutions).
• Input to Primary auditory
cortex is from medial
geniculate nucleus (MGN) of
the thalamus.
• Auditory radiation undergoes
partial decussation in the brain
stem before it reaches the
(MGN).
PRIMARY AUDITORY
CORTEX
• Lies behind the primary
auditory cortex.
• Continuous posteriorly
with the second motor
speech (Wernicke’s)
area.
• Here the heard sounds or
words are interpreted.
• Lesion:
• Sensory aphasia;
(inability to recognize the
meaning of sounds or
words with hearing
unimpaired.
SECONDARY AUDITORY CORTEX
or
AUDITORY ASSOCIATION CORTEX
• Lies on medial surface of
the occipital lobe.
• In close relation to the
calcarine sulcus.
• It extends to the occipital
pole.
• Brodmann’s area 17
• It receives optic radiation
from lateral geniculate
nucleus (LGN) of the
thalamus.
• Each lateral half of the
visual field is represented in
the visual cortex of the
contralateral hemisphere.
• Lesion: Homonymous
hemianopia.
PRIMARY VISUAL CORTEX
• Brodmann’s areas
18,19 are called
visual association
cortex.
• They are
interpretive to the
visual image.
• Lesion: visual
agnosia, (inability
to recognize a
seen object).
VISUAL ASSOCCIATION
CORTEX
SECOND MOTOR SPEASCH AREA (Wernicke’s area)
• Also, known as language
area.
• Lies in dominant
hemisphere.
• Lies in the inferior parietal
lobule & auditory
association area.
• Lesion:
• Sensory or receptive
aphasia
• (Lack of comprehension of
words by vision or hearing)