CEREBRAL CORTEX

AAKRITI DHAKALBPT

INTRODUCTION;.The outer layer of gray matter of cerebrum is cerebral cortex. The outer layer of cerebral cortex folds to create gyri and sulci.The cerebrum or cortex is the largest part of brain,associated with higher brain function such as thought and action.

what is grey matter and white matter ??? The CNS has two kinds of tissue;grey matter and white matter. Grey matter is pinkish grey colour in the living brain containing cell bodies,dendrites and axon terminals of neurons so it is where all synapse are.White matter is made of axons connecting different parts of grey matter to each other.

Cerebrum is the principal and the most anterior part of the brain in the vertebrates, located in the front part of the cranial cavity.

It is made of two cerebral hemispheres which are incompletely separated from each other by the median longitudinal fissures.

The two Rt and lft hemispheres are connected to each other across the median plane by the corpus callosum which passes messages betwn two halves of hemisphere.

The Rt half of the cerebrum controls the left side of the body and vice versa.

Each hemisphere contains a cavity, called lateral ventrical.

Parts of cerebrum1. Sulci: A depression, sulcus in the surface area

allows for continued growth of brain thus allows for function of brain to continue growing.

2. Gyri: elevated ridges “winding” around the brain3. Fissures:Types of fissures:I. Longitudinal :divides two cerebral hemispheresII. Transverse: separates cerebrum from cerebellumIII. Sylvian/lateral:divides temporal from parietal

and frontal lobes4. Hemispheres – Rt and lft

Lobes of cerebrumEach cerebral hemispheres is divided into four lobes-1.Frontal lobe2.Parietal lobe3.Occipital lobe4.Temporal lobe

Functional or cortical areas of cerebral cortexThere are three basic functional divisions of cerebral cortex:1. Motor areas: the primary motor area, give rise

to contration of skeletal musculature.2. Sensory areas: in these areas, electrical activity

can be recored if appropriate sensory stimulus is applied to a particular part of the body .

3. Association areas: these areas integrate and analyse the respones from various sources.

Surface/lobe Sulci GyriSuperolateral surface:1. Frontal lobe

A. PrecentralB. Superior frontalC. Inferior frontal

a. Precentralb. Superior frontalc. Middle frontald. Inferior frontal

2. Parietal lobe A. PostcentralB. Intraparietal

a. Postcentral b. Superior parietal

lobulec. Inferior parital

lobule i. The anterior,

supramarginalii. The middle,

angulariii. The posterior,

over the upturned end of inferior temporal sulcus

FUNCTIONAL AREAS OF BRAIN;

1.FRONTAL LOBEThe frontal lobe forms one third of the cortical surface.Frontal lobe of cerebral cortex is divided into two parts;

1.Precentral Cortex- a.primary motor area(4,4s) b.premotor area(6,8,44,45) c.supplementary motor area

2.Prefrontal Cortex- (9,10,11)

frontal lobe

FRONTAL LOBE

AREA AREA NO.

LOCATION FUNCTION

EFFECT OF LESION

PRECENTRAL CORTEX

1.primary motor area

4

4s

Precentral gyrus and paracentral lobule

Controls voluntary activities of the opposite half of body.

Suppresses the extra impulse produced by area 4 and prevents exaggeration of movements.

Contralateral paralysis and Jacksonian fits

Front

al Lobe

Area Area

no.

Location

Representation of body

parts

Function Effect of

lesion

Precentral cortex

2.Pre-motor area

6 Posterior parts of superior middle and inferior frontal gyri

_ Concerned with coordination of movements initiated by area 4. Controls extra-pyramidal system

Often mixed pyramidal effect

FRONTAL LOBE

AREA AREA NO LOCATION FUNCTION EFFECT OF LESION

Precentral cortex

Premotor area (frontal eye field)

8 - Concerned with

conjugate movement of eyeballs

Conjugate movements of eyes are

lost.

Lobe Area Area

no.

Location Representation of body

parts

Function Effect of

lesionPrecentral cortex

Motor speech area(Broca’s area)

44, 45

Para triangularis and pars opercularis

_ Controls the spoken speech.Responsible for movements of tongue,lips and larynx.

Aphasia (motor)

SUPPLEMENTARY MOTOR AREA;• In association with premotor area provides

attitudinal movements,fixation movement of different segments of the body and positional movements of head and eyes.

Lobe Area Area

no.

Location Representation of body

parts

Function Effect of

lesionFrontal lobe

5.Pre-frontal area

9,10,11, 12, 13, 14, 23, 24, 29 and 32

The remaining large, anterior part of frontal lobe

_ Controls emotion, concentration attention and judgment

Loss of orientation,lack of initiation and mental alertness.

FRONTAL LOBE SYNDROME• The injury or ablation of prefrontal cortex leads to a condition

called frontal lobe syndrome.The features of this syndrome are;• 1.Emotional instability.• 2.lack of concentration and fixing attention occur• 3.lack of initiation and difficulty in planning any course of action.• 4.loss of moral and social science.• 5.Failure to realize the seriousness of the condition.The subject

has the sense of well beingand also has flight of ideas.• 6.Apart from mental disorders,other functional abnormalities like; i. Hyperphagia ii.Incontinence iii.slight tremor iv.Disturbances in orientation

PARIETAL LOBE• The parietal lobe extends from central sulcus and

merges with occipital lobe behind and temporal lobe below.

• Parietal lobe is divided into 3 functional areas; a.Somesthetic area I (1,2,3) b.Somesthetic area II c.Somesthetic association area (5,7)

Lobe Area Area no.

Location Function Effect of

lesionParietal lobe

Somesthetic area 1

3, 1, 2

Postcentral gyrus and paracentral lobule

perception of exteroceptive (touch, pain,pressure and temperature) and proprioceptive impulses.Area 1 is concerned with sensory perception and areas 2&3 are involved in the integration of these sensations.

Loss of appreciation of the impulses received,loss of sensations in the opposite side of body.

PARIETAL LOBE (CONT)SOMESTHETIC AREA II

It is situated in postcentral gyrus below the area of face of somesthetic area I.This area receives sensory impulses from somesthetic area I and from thalamus.Concerned with perception of sensation.SOMESTHETIC ASSOCIATION AREA

It is situated posterior to postcentral gyrus.It has two areas -5 & 7. Concerned with synthesis of various sensations perceived by somesthetic area I.The lesion of this area causes ASTEREOGNOSIS.