anatomy and physiology of brain

1. BRAINSAYALI GUJJEWAR
MPT II

2. NERVOUS SYSTEM

3.  Central nervous system which comprises of brain and spinal cord is
responsible for integrating, coordinating the sensory information and
ordering appropriate motor actions. It is the seat of learning, memory,
intelligence and emotions.
 Peripheral nervous system includes 12 pairs of cranial nerves and 31
pairs of spinal nerves. These provide afferent impulses to CNS and
carries efferent impulses to muscles, glands and blood vessels.
 Afferent component provides sensory information to CNS.
 Efferent component carries motor information to muscles, glands,
blood vessels and heart via somatic nervous system for the control of
skeletal muscles and autonomic nervous system for the control of
heart, smooth muscle of the organs, glands and blood vessels.

4. BRAIN
 The human brain is the central organ of the human nervous system,
and with the spinal cord makes up the central nervous system.
 It controls most of the activities of the body, processing, integrating,
and coordinating the information it receives from the sense organs,
and making decisions as to the instructions sent to the rest of the
body.
 Weight of the brain is 1500 grams i.e. about 2% of the total body
weight. It is 167 mm long, 93 mm high and 140 mm wide
(approximately).

5. PARTS OF THE BRAIN

6. CEREBRUM
 Cerebrum is made up of two cerebral
hemispheres which are incompletely
separated from each other by
longitudinal fissure.
 The two hemispheres are connected to
each other across the median plane by
the corpus callosum.
 Each hemisphere contains a cavity
called the lateral ventricle.

7. LOBES OF CEREBRAL HEMISPHERES
FRONTAL LOBE
1. Prospective memory 4. Movement control
2. Decision making 5. Speech and language
3. Personality
PARIETAL LOBE
1. Interpreting simple somatosensory signals 2. Learning 3. Language
4. Spatial recognition 5. Motor planning action
6. Sensorimotor planning 7. Stereognosis
TEMPORAL LOBE
1. Auditory processing and perception 2. Object perception and recognition
3. Language recognition 4. Declarative memory
OCCIPITAL LOBE
1. Visual processing and interpretation

8. SULCI AND GYRI
 Cerebral cortex is folded into gyri which are separated from each
other by sulci.
 This pattern increases the surface area of the cerebral cortex and
allows more neurons to be packed into the cortex which increases the
brain's ability to process information.
 The total area of the cortex is estimated to be more than 2000 cm2,
and approximately two-thirds of this area is hidden from the surface
within sulci.

12. FUNCTIONAL AREAS OF CEREBRAL
CORTEX
MOTOR AREA
 The primary motor area has been identified on the basis of elicitation of motor responses at a low
threshold of electric stimulation which give rise to contraction of skeletal musculature.
 These areas give origin to corticospinal and corticonuclear fibres.
SENSORY AREA
 In these areas, electrical activity can be recorded if appropriate sensory stimulus is applied to a
particular part of the body.
 The ventral posterior nucleus is main source of afferent fibres for the first sensory area. This
thalamic nucleus is the site of termination of all the fibres of the medial lemniscus and of most of
the spinothalamic and trigeminothalamic tracts.
ASSOCIATION AREA
 In these regions, the direct sensory or motor responses are not elicited.
 These areas integrate and analyse the responses from various sources. Many such areas are known
to have motor or sensory functions.
 The motor and sensory functions also overlap in the same region of cortex. If the motor function is
predominant, it is known as motor-sensory and where sensory function is predominant, it is called
sensori-motor.

16. MOTOR AREA
PRIMARY MOTOR AREA
 Located in the precentral gyrus, including the anterior wall of central sulcus, and in the anterior
part of paracentral lobule on the medial surface of cerebral hemispheres.
 Corresponds to area 4 of Brodmann.
 Electrical stimulation of primary motor area elicits contraction of muscles that are mainly on the
opposite side of body.
 Although cortical control of musculature is mainly contralateral, there is significant ipsilateral
control of most of the muscles of the head and axial muscles of the body.
 The contralateral half of the body is represented as upside down, except the face.
 The pharyngeal region, tongue are represented in the most ventral and lower part of precentral
gyrus, followed by the face , hand, arm, trunk and thigh.
 The remainder of leg, foot and perineum is on the medial surface of hemisphere in the
paracentral lobule.

17.  Another significant feature in this area is that the size of the cortical area for a particular part of
the body is determined by the functional importance of the part and its need for sensitivity and
intricacy of the movements of that region.
 The area for the face, especially the larynx and lips, is therefore disproportionately large and a
large area is assigned to the hand particularly the thumb and index finger.
 Movements of the joints are represented rather than the individual muscles.

18. PREMOTOR AREA
 Coincides with the Brodmann’s area 6.
 Situated anterior to motor area in the superolateral and medial surfaces of the hemisphere.
 Contributes to motor function by its direct contribution to the pyramidal and other descending
motor pathways and by its influence on the primary motor cortex.
 Programmes skilled motor activity and directs the primary motor area in its execution.
The premotor and primary motor areas are together referred to as the primary somato-motor area
(Ms I).
Both these areas give origin to corticospinal and corticonuclear fibres and receive fibres from
cerebellum after relay in ventral intermediate nucleus of thalamus.
SUPPLEMENTARY MOTOR AREA (Ms II)
 Predominantly motor in function.
 This motor area is in the part of area 6 that lies on the medial surface of the hemisphere
anterior to the paracentral lobule.
 Its stimulation produces bilateral movements.
 Different parts of the body are represented in this area.

19. MOTOR SPEECH AREA (BROCA’S AREA)
 Occupies opercular and triangular portions of the inferior frontal gyrus corresponding to the
area 44 and 45 of Brodmann.
 Present on left side in 98% of right handed persons.
 In 70% of left handers, it is present in the left hemisphere.
 Only in 30% it is present in right hemisphere.
FRONTAL EYE FIELD
 lies in the middle frontal gyrus just anterior to precentral gyrus.
 It is the lower part of area 8 of Brodmann on the lateral surface of cerebral hemisphere,
extending slightly beyond that area.
 Electrical stimulation of this area causes deviation of both the eyes to the opposite side. This
is called conjugate movements of the eyes.
 Movement of the head and dilatation of pupil may also occur.
 Connected to the cortex of occipital lobe which is concerned with vision.

20. PREFRONTAL CORTEX
 Large area lying anterior to precentral area.
 Includes the superior, middle and inferior frontal gyri, medial frontal gyrus, orbital gyri and
anterior half of the cingulate gyrus.
 Includes brodmann’s area 9, 10, 11 and 12.
 Connected to other areas of cerebral cortex, corpus striatum, thalamus and hypothalamus.
Also, connected to the cerebellum through the pontine nucleus.
 Controls emotions, concentration, attention, initiative and judgement.

21. SENSORY AREAS
 FIRST SOMESTHETIC AREA
 SECOND SOMESTHETIC AREA
 SOMESTHETIC ASSOCIATION CORTEX
 RECEPTIVE SPEECH AREA OF WERNICKE

22. FIRST SOMESTHETIC AREA (Sm I)
 Occupies post central gyrus on the superolateral surface of the cerebral hemisphere and posterior
part of paracentral lobule on the medial surface.
 Corresponds to area 3, 1 and 2 of Brodmann.
 The representation of the body in this area in that contralateral half of the body is represented
upside down except the face.
 The area of the cortex that receives sensations from a particular part of body is not proportional to
the size of that part, but rather to the intricacy of sensations received from it.
 Thus, the thumb, fingers, lips and tongue have a disproportionately large representation.
 The different sensations i.e. cutaneous and proprioceptive are represented in different parts
within the sensory area.

23. SECOND SOMESTHETIC AREA (Sm II)
 Situated in the superior lip of the posterior ramus of lateral sulcus with postcentral gyrus.
 Parts of the body are represented bilaterally.
SOMESTHETIC ASSOCIATION CORTEX
 Is in the superior parietal lobule on the superolateral surface of the hemisphere and in the
precuneus on the medial surface.
 Coincides with areas 5 and 7 of Brodmann.
 Data pertaining to the general senses are integrated, permitting a comprehensive assessment of
the characteristic of an object held in hand and its identification without visual aid.
RECEPTIVE SPEECH AREA OF WERNICKE
 Sensory language area
 Consists of auditory association cortex and
of adjacent parts of the inferior parietal lobule.
 Corresponds to area 22 of Brodmann.

24. BRAINSTEM
 The brainstem consists of the pons, medulla oblongata and midbrain.
 It connects the spinal cord to cerebrum.
 The ascending and descending tracts pass through the components of the brainstem.
 Medulla oblongata consists of the respiratory and vasomotor centres.
 Midbrain contains nuclei of oculomotor and trochlear nerves.
 Pons has the nuclei of trigeminal, abducent, facial and statoacoustic nerves.
 Medulla houses the nuclei of glossopharyngeal, vagus, accessory and hypoglossal nerves.

26. CEREBELLUM
 The cerebellum is the largest part of the hindbrain located in the
posterior cranial fossa behind the pons and medulla.
 Controls the same side of the body directly or indirectly.

27.  The cerebellum consists of two cerebellar hemispheres that are
united to each other through a median vermis.
 Each hemisphere is divided into 3 lobes: anterior lobe,
middle/posterior lobe and flocculonodular lobe.
 Cerebellum is divided into different parts by fissures:
- Horizontal fissure: separates the superior surface from the inferior
surface.
- Primary fissure: separates the anterior lobe from the middle lobe on
the superior surface.
- Posterolateral fissure: separates the middle lobe from the
flocculonodular lobe on the inferior surface.

28. MORPHOLOGICAL AND FUNCTIONAL
DIVISIONS OF CEREBELLUM
• Made up of flocculonodular lobe and lingula.
• Controls the axial musculature and the bilateral movements used for
locomotion and maintenance of equilibrium.
ARCHICEREBELLUM
• Made up of anterior lobe (except lingula), and the pyramid and uvula of
the inferior vermis.
• Controls tone, posture and crude movements of the limbs.
PALEOCEREBELLUM
• Made up of posterior/middle lobe except the pyramid and uvula of the
inferior vermis.
• Primarily concerned with the regulation of fine movements of the body.
NEOCEREBELLUM

29. ZONES OF THE CEREBELLUM
 Functionally, the anterior and posterior lobes are organized into 3
longitudinal zones.
Lateral
• Connected
with
association
areas of brain
• Involved in
planning and
programming
muscular
activities
Intermediate
• Concerned
with control
of muscles of
hands,
fingers, feet
and toes
Vermis
• Concerned
with control
of muscles of
trunk, neck,
shoulders and
hips
Flocculonodular
lobe
• Functions with
vestibular
system in
controlling
equilibrium

30. CONNECTIONS OF CEREBELLUM
 Fibers entering or leaving the cerebellum are grouped to form three peduncles ( middle, inferior &
superior) which connect the cerebellum to the midbrain, pons and medulla.
 Middle and inferior peduncles are chiefly afferent to the cerebellum and superior peduncle is chiefly
efferent in nature.

31. FUNCTIONS OF CEREBELLUM
 Coordinates voluntary movements so that they are smooth, balanced
and accurate.
 Controls tone, posture and equilibrium.
 All sensory information of muscles, joints, cutaneous, auditory and
visual parts are relayed here.
 Functions as the comparator. It receives information from cerebrum
and spinal cord, corrects and modifies ongoing movements through
thalamocortical projections, reticulospinal and rubrospinal tracts.
 Fine tuning of motor performance for pecise movements.
 Helps in planning and production of skilled movements along with
cerebrum.