Cerebral cortex perform a proper function without it there is serious error may occur if these area are damaged, the reticulur formation is the ON/OFF our brain AWAKE/SLEEP

1. 9-12-2019

2. Introduction:
• Consists of two hemispheres.
• Surface area of cerebral cortex in human beings is 2.2 sq m.
• Vertical fissure: is deep furrow or groove that separates
both cerebral hemisphere.
• Corpus callosum is the broad band of commissural fibers,
connecting the two hemispheres.
• Surface of the cerebral cortex is characterized by
complicated pattern of a- sulci (slight depression or groove)
and b- gyrus (raised ridge).
• Cerebral cortex consists of gray matter that surrounds the
deeper white matter.
• It is formed by different types of nerve cells along with
their processes and neuroglia.
• It is not uniform throughout.

3. LAYERS OF CEREBRAL CORTEX:
• According to Economo, the cerebral cortex is
formed by six layers of structures:
1. Molecular or Plexiform Layer.
2. External Granular Layer.
3. Outer Pyramidal Layer.
4. Internal Granular Layer.
5. Ganglionic Layer or Internal Pyramidal Layer.
6. Fusiform Cell Layer.

4. PARTS OF CEREBRAL CORTEX:
1. Neocortex or isocortex or neopallium.
• New structure of cerebral cortex.
• Major portion of cerebral cortex.
• Have all six layers of cerebral cortex.
2. Allocortex.
• Oldest structure of cerebral cortex.
• Less than six layers of structures.
• Two divisions: archicortex and paleocortex,
which form the parts of limbic system.

5. LOBES OF CEREBRAL CORTEX:
1. Frontal lobe. 2. Parietal lobe.
3. Occipital lobe. 4. Temporal lobe.
• Lobes of each hemisphere are demarcated by four
main fissures and sulci:
1. Central sulcus or Rolandic fissure between frontal
and parietal lobes.
2. Parieto-occipital sulcus between parietal and
occipital lobe
3. Sylvian fissure or lateral sulcus between parietal
and temporal lobes
4. Callosomarginal fissure between temporal lobe
and limbic area.

8. 1- FRONTAL LOBE OF CEREBRAL CORTEX:
• One third of the cortical surface.
A. Precentral cortex, which is situated posteriorly.
B. Prefrontal cortex, which is situated anteriorly.
• PRECENTRAL CORTEX:
• Excitomotor cortex or area.
• Precentral cortex is further divided into three
functional areas:
1. Primary motor area: (area 4,4S).
2. Premotor area: (areas 6, 8, 44 and 45).
3. Supplementary motor area.

9. Function of PRECENTRAL CORTEX Area:
A- Function of area 4:
1. Center for movement.
2. Activates both α-motor neurons and γ-motor neurons.
B- Function of area 4S:
1. Suppressor area 4.
2. Inhibits exaggeration of movements.
C- Function of area 6:
1. Coordination of movements initiated by area 4.
2. Center for extrapyramidal system.
D- Function of area 8:
1. Conjugate movement of eyeballs.
2. Opening and closing of eyelids, pupillary dilatation.
3. Lacrimation.
E- Function of area 44,45 (Broca area):
1. Motor area for speech.
2. Movements of tongue, lips and larynx.

10. F- Function of supplementary motor area:
1. Raising the contralateral arm, turning the head and eye and movements
of synergistic muscles of trunk and legs.
2. Coordinated skilled movements.
• PREFRONTAL CORTEXOR ORBITOFRONTAL CORTEX:
• Silent area or association area.
• Areas: 9, 10, 11, 12, 13, 14, 23, 24, 29 and 32.
1. Changes in the activity of digestive, cardiovascular, respiratory and
excretory systems and other autonomic functions.
2. Center for fear.
3. Center for emotion, learning, memory and social behavior.
4. Short-term memories.
5. Center for planned actions.
6. Seat of intelligence(organ of mind).
7. Responsible for the personality of the individuals.
Functions of Prefrontal Cortex:

11. FRONTAL LOBE

12. 2- PARIETAL LOBE:
• Parietal lobe extends from central sulcus and merges
with occipital lobe behind and temporal lobe below.
• This lobe is separated from occipital lobe by parieto-
occipital sulcus and from temporal lobe by Sylvian
sulcus.
• Parietal lobe is divided into three functional areas:
A. Somesthetic area I
B. Somesthetic area II
C. Somesthetic association area.
• A part of sensory motor area is also situated in
parietal lobe.

13. A) SOMESTHETIC AREA I (somatosensory area):
• Also called primary somesthetic or primary sensory area.
• Somesthetic area: 3 (anterior), 1 and 2 (posterior).
• Functions of Somesthetic Area I:
1. Perception and integration of cutaneous and kinesthetic
sensations.
2. Proprioceptors of opposite side.
3. Sends sensory feedback to the premotor area.
4. Movements of head and eyeballs.
5. Discriminative functions.
B) SOMESTHETIC AREA II:
• Also called secondary somesthetic area or somatosensory area
II
• Functions of Somesthetic Area II:
1. Role of this area is not clear.
2. Receives sensory impulses from somesthetic area I and from
thalamus directly.
3. But it concern with perception of sensation.

14. C) SOMESTHETIC ASSOCIATION AREA:
• Situated posterior to postcentral gyrus, above the auditory
cortex and in front of visual cortex.
• It has two areas, 5 and 7.
• Functions of Somesthetic Association Area:
• Synthesis of various sensations perceived by somesthetic area
I.
• Center for combined sensations like stereognosis.
D) SENSORY MOTOR AREA:
• Sensory area of cortex extends anteriorly into motor area in
precentral gyrus of frontal lobe.
• Function of sensory motor area:
• Store the timing and programming of various sequential
movements of complicated skilled movements

15. PARIETAL LOBE
1. Cutaneous and kinesthetic sensations
2. Discriminative functions
3. Perception of sensation
4. Stereognosis
5. Storing, timimg, and programmed skilled movement.

16. 3- TEMPORAL LOBE:
• Temporal lobe of cerebral cortex includes three functional
areas:
A. Primary auditory area
B. Secondary auditory area or auditopsychic area
C. Area for equilibrium.
A) PRIMARY AUDITORY AREA:
• Areas: 41, 42, and Wernicke area.
• Functions of Primary Auditory Area:
1. Perception of auditory impulses (41 and 42), analysis of
pitch and determination of intensity and source of sound.
2. Wernicke area is responsible for the interpretation of
auditory sensation with the help of secondary auditory
area (area 22).
3. Sending the information to Broca area.

17. B) SECONDARY AUDITORY AREA:
• Also called or auditopsychic area or auditory association
area.
• Area 22.
• Functions of Secondary Auditory Area:
1. Concerned with interpretation of auditory sensation along
with Wernicke area.
2. Storage of memories of spoken words.
C) AREA FOR EQUILIBRIUM:
• Area for equilibrium is in the posterior part of superior
temporal gyrus.
• It is concerned with the maintenance of equilibrium of the
body.
• Stimulation of this area causes dizziness, swaying, falling
and feeling of rotation.

18. TEMPORAL LOBE
1. Perception of auditory impulses
2. Interpretation of auditory sensation
3. Storage of memories of spoken words
4. Maintenance of equilibrium of the body.

19. 4- OCCIPITAL LOBE:
• Called the visual cortex.
• Occipital lobe consists of three functional areas:
A. 1. Primary visual area (area 17)
B. 2. Secondary visual area or visuopsychic area (area 18)
C. 3. Occipital eye field (area 19).
• Functions of Occipital Lobe:
1. Primary visual area (area 17) is concerned with perception of
visual sensation
2. Secondary visual area (area 18) is concerned with
interpretation of visual sensation and storage of memories
of visual symbols.
3. Occipital eye field (area 19) is concerned with reflex
movement of eyeballs. It is also concerned with associated
movements of eyeballs while following a moving object.

20. OCCIPITAL LOBE
1. Perception of visual sensation
2. Interpretation of visual sensation and
storage of memories of visual symbols
3. Movements of eyeballs while following a
moving object

24. Cortical homunculus:
• The cortical homunculus: is a physical
representation of our body in our brain.
There are two types of these neurological
‘maps’:
1. Sensory pathways.
2. Motor pathways.
• If our bodies actually looked like our brain’s
representation, we would look very strange
indeed.

28. Introduction:
• Limbic system is a complex system of cortical and
subcortical structures that form a ring around the hilus
of cerebral hemisphere.
• Limbus means ring.
• Limbic system is primarily related to emotional part of
our life and is extensively concerned with memory.
• Structures of limbic system are classified into four
groups:
1. Archicortex: oldest structure - concerned with memory.
2. Paleocortex: concerned with olfaction.
3. Juxtallocortex or mesocortex.
4. Subcortical structures

30. FUNCTIONS OF LIMBIC SYSTEM:
1. Olfaction: (piriform cortex and amygdaloid nucleus form the
olfactory centers).
2. Regulation of endocrine glands.
3. Regulation of autonomic functions: (heart rate, blood
pressure, water balance, and body temperature).
4. Regulation of food intake: along with amygdaloid complex.
5. Control of circadian rhythm.
6. Regulation of sexual functions.
7. Role in emotional state: (maintained by hippocampus along
with hypothalamus).
8. Role in memory.
9. Role in Motivation: (Reward and punishment centers present
in hypothalamus and other structures of limbic system).

32. Introduction:
• Reticular formation is a diffused mass of
neurons and nerve fibers, which form an ill-
defined meshwork of reticulum in central
portion of the brainstem.
• Reticular formation is situated in brainstem.
• Reticular formation is constituted by 5 groups
of nuclei.
• All these nuclei are structurally and
functionally distinct.

33. 1- RAPHE GROUP:
• Secrete serotonin (5-hydroxytryptamine), which is
an inhibitory neurotransmitter.
2- PARAMEDIAN GROUP:
• Concerned with motor functions.
3- LATERAL GROUP:
• Receive sensory signals from the cranial nerves,
cerebellum and spinal cord.
4- MEDIAL GROUP:
• Associated with motor functions.
5- INTERMEDIATE GROUP:
• Concerned with autonomic regulation of respiration,
heart rate and blood pressure.

34. DIVISIONS OF RETICULAR
FORMATION:

35. FUNCTIONS OF RETICULAR FORMATION
• Based on functions, reticular formation along with its
connections is divided into two systems:
A. Ascending reticular activating system
B. Descending reticular system.
Functions of ARAS:
1. Concerned with arousal phenomenon, alertness, maintenance
of attention and wakefulness.
2. The ARAS also causes emotional reactions.
3. Regulating the learning processes and the development of
conditioned reflexes.
• “Tumor or lesion in ARAS leads to sleeping sickness or coma”.
• Functionally, descending reticular system is divided into two
subdivisions:
1. Descending facilitatory reticular system.
2. Descending inhibitory reticular system.
(AWAKE)
(SLEEP)

36. • Descending Facilitatory Reticular System:
1. Facilitation of somatomotor activities: (ncreased muscle tone,
movements of the body and wakefulness and alertness by
activating the ARAS)
2. Facilitation of vegetative functions: (facilitation of the
autonomic functions such as cardiac function, blood pressure,
respiration, gastrointestinal function and body temperature).
• Descending Inhibitory Reticular System:
1. Control of somatomotor activities: (inhibits the gamma motor
neurons of spinal cord and decreases muscle tone,
smoothness and accuracy of voluntary movements, inhibiting
the motor neurons of spinal cord and controls the reflex
movements).
2. Control of vegetative functions: (inhibition of several
autonomic functions such as cardiac function, blood pressure,
respiration, gastrointestinal function and body temperature.)