by prof. saeed abuel makarem saeed abuel makarem

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By Prof. Saeed Abuel Makarem CEREBRU M CEREBRAL HEMISPHERE OR

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Page 1: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

By Prof. Saeed Abuel Makarem

CEREBRUM

CEREBRAL HEMISPHEREOR

Page 2: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

CEREBRUM• 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.

Page 3: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

CEREBRUM : SURFACES• 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.

Page 4: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

CEREBRUM: BORDERS• 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.

Page 5: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

CEREBRUM3 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.

Page 6: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

SULCI ON THE LATERAL SURFACE

• 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

Page 7: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

GYRI 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

Page 8: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem
Page 9: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

SULCI ON THE MEDIAL 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.

Page 10: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

GYRI 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.

GS

BODY

Page 11: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

SULCI ON THE INFERIOR 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..

Page 12: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

GYRI 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.

Page 13: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

IMPORTANT CENTERS OF THE CEREBRAL CORTEX

MAIN FUNCTIONAL AREAS OF THE CEREBRAL CORTEX

OR

Page 14: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

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.

Page 15: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

Posterior part of the cerebrum receives sensory information in:

1- Parietal lobe (Somatosensory),

2- Occipital lobe (Vision),

3- Temporal lobe (Hearing).

For identification by touch, sight & hearing.

THEN ?

Page 16: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

Storage & Retrieval of information

• Information is elaborated to the association cortex, (at the meeting of the parietal, temporal & occipital)

• The limbic system (medial part of cerebrum) enable storage & retrieval of the information processed in the posterior cortex.

Page 17: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

MOTOR AREA• 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).

Page 18: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

PRIMARY MOTOR CORTEX (PMC)

• 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.

Page 19: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

• 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 upper limb, & head, neck 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)

Page 20: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

PREMOTOR CORTEX• 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.

6

Page 21: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

SUPPLEMENTARY MOTOR CORTEX

• 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

Page 22: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

FRONTAL EYE FIELD• 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.

Page 23: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

MOTOR SPEECH AREABROCA’S AREA

• 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)

Page 24: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem
Page 25: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

PREFRONTAL CORTEX• The rest of the frontal lobe.

• Lies anterior to premotor area.

• It has rich connections with parietal, temporal and occipital cortex.

• Functions:• Intellect.• Judgment.• Prediction.• Motivation• Planning of behaviour.

Page 26: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

PRIMARY SOMATOSENSORY 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.

Page 27: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

• VPN receives:• 1-Medial lemniscus • (Fine touch & proprioception).• 2-Spinal lemniscus• (coarse touch & pressure).• 3-Spiothalamic tract • (pain & temperature).• 4- Trigeminothalamic tract

(general sensation from head)

Page 28: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

PRIMARY AUDITORY CORTEX

• 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).

Page 29: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

SECONDARY AUDITORY CORTEXor

AUDITORY ASSOCIATION 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.

Page 30: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

PRIMARY VISUAL 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 hemianopsia.

Page 31: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

VISUAL ASSOCCIATION 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).

Page 32: By Prof. Saeed Abuel Makarem Saeed Abuel Makarem

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)