This document provides an overview of the nervous system, including its main parts and the structure and functions of the central nervous system. The central nervous system consists of the brain and spinal cord. The brain is divided into the forebrain, midbrain, and hindbrain. The major divisions of the cerebrum are described in detail, including the lobes and functional areas. The functions of other parts of the brain like the cerebellum, brain stem, and hypothalamus are also summarized briefly.

1. Dr. SHAROJ
KHAN
MBBS
INTRODUCTION TO
NERVOUS SYSTEM

2. Parts of Nervous System
 Divided into 3 parts
- Central Nervous system (consisting of Brain
and spinal cord)
- Peripheral nervous system (nerves made of
neurones that carry information to and from
central nervous system.
- Autonomic Nervous System (part of the
nervous system concerned with the innervation
of involuntary structures, such as the heart,
smooth muscle, and glands within the body.

3. Major Divisions of the Central
Nervous System

Brain
Forebrain
Cerebrum
Diencephalon
(between brain)
Midbrain
Hindbrain
Medulla
oblongata
Pons
Cerebellum
Spinal cord
Cervical
segments
Thoracic
segments
Lumbar
segments
Sacral
segments
Coccygeal

4. CEREBRUM
 cerebrum is the largest part of the brain,
situated in the anterior and middle cranial
fossae of the skull and occupying the whole
concavity of the vault of the skull. There are 2
hemispheres.
 2 hemispheres are divided by a deep cleft, the
longitudinal cerebral fissure,into right and left
cerebral hemispheres, each containing one of
the lateral ventricles.
 Deep in the brain the hemispheres are
connected by a mass of white matter (nerve
fibres) called as corpous callosum. The
superficial part of cerebrum is composed of
nerve cell bodies or grey matter, forming the
cerebral cortex, and the deep er layer consist
of nerve fibres or white matter.

5.  CEREBRAL CORTEX
 Surface is highly
convulated with
bulges known as gyri
asnd spaces
separating the gyri is
known as sulci.

6.  Each hemisphere is divided into lobes which
take names of the bones of the cranium under
which they lie.
 Frontal
 Parietal
 Temporal
 occipital

8. Interior of the cerebrum
 Surface of cerebral cortex is grey matter. Within
cerebrum the lobes are connected by masses of
nerve fibres or tracts, which makeup white matter
of brain
 Afferent and efferent fibres linking different parts
of brain and spinal cord are as follows:
 Association (arcuate) tracts connectone gyrus to
another, some are adjacent and some are distant.
 Commisural tracts- connect corresponding area of
two hemispheres most important one is corpus
callosum.
 Projection tracts connect the cerebral cortex with
grey matter of lower parts of the brain and with the
spinal cord, e.g. Internal capsule

10. Functions of cerebral cortex
 Mental activities involved in memory, intelligence,
sense of responsibility, thinking, reasoning, moral
sense and learning are attributed to higher
centres.
 Sensory perception..( pain, touch, temperature,
pressure, sight, hearing, taste, smell)
 Initiation and control of skeletal muscle
contraction.

11. Functional areas of the cerebral
cortex
 Primary motor cortex:
 lies in frontal lobe, anterior to central sulcus.
 Cell bodies are pyramid shape (Betz cell) and initiate skeletal muscle
contraction.
 Nerve fibre (upper motor neurone) from betze cell passes downward
 Internal capsule medulla oblongota ( where it crosses to
opposite side then descends
 Spinal cord
 Then nerve impulse crosses synapse to stimulate a second neurone
(lower motor neurone) that terminates at the motor end plate of a
muscle fibre.
 In motor area of cerebrum the body is represented upside down, i.e.
the uppermost cells control the feet and those in the lowermost
control head, neck face and figers.

12. The motor homunuculus in precentral
gyrus
 Muscles of head
represented most
ventrally closest to
lateral fissure.
 Dorsally regions of
neck, upper limb and
trunk on lateral
aspect.
 Medial aspect is for
motor representation
for the pelvis and
lower limb.
 Supplied by branches
of anterior cerebral

13.  Broca’s Area-
 Motor speech area.
 This is situated in the
frontal lobe just above
the lateraql sulcus
and control muscle
movements
necessary for speech.
It is dominant in the
left hemisphere in
right handed people
and vice versa.

14. Sensory areas of the cerebral cortex
 The somato sensory
area:
 Area behind central
sulcus
 Sensation of pain,
temperature, pressure
and touch awareness
of muscular
movement and the
position of joints are
received.
 Auditory area:
 Lies below lateral
sulcus in temporal
lobe
 Nerve cell receive
and interpret
nimpulses transmitted
from inner ear by 8th
nerve

15.  Olfactory (smell) area:
 Inside temporal lobe
where impulses from
nose, transmitted by
1st Cranial nerve are
received and
interpreted.
 Taste area:
 Lies above lateral
sulcus in deep layers
of the somatosensory
area.
 Impulse from sensory
receptors in taste
buds are received
and perceived as
taste.

16.  Visual area:
 Behind parieto
occipital sulcusand
includes the part of
occipital lobe.
 Optic nerves (2nd
cranial nerve receives
and interprets the
impulses as visual
impressions.

17. Association areas
 Pre-frontal cortex
 Located in front of pre
motor area.
 Represents 1/4th of
entire cerebral cortex
in human brain.
 Involved in planning
and emotional
aspects of behaviour.
 The premotor area
 Lies in frontal lobe
anterior to motor area.
 Neurones here
coordinate movement
initiated by the
primary motor cortex,
ensuring the learned
pattern of movement
can be repeated.

18. Association Areas
 Wernicke’s (sensory
speech) area
 Located in temporal
lobe adjacent to the
parieto occipital-
temporal area. It is
here that all the
spoken word is
perceivced, and
comprehension and
intelligence are based
 The Parieto- Occipito
temporal area-
 Lies behind somato
sensory area and
includes most of
parietal lobe.
 Functions
 Spatial awareness
 Interpreting written
language

19.  The sensory
Homunuculus in Post
central Gyrus.
 Similar somatotropic
representation of
body
 Head, neck, upper limbs
and trunk laterally.
 Pelvis and lower limbs
medially.

20. Some Other Parts of Cerebral cortex
 Thalamus
 Thalamus is a large ovoid mass of gray matter.
 Sensory input from the skin viscera and special sense
organs is relayed to the thalamus before redistribution to
the cerebrum.
 Basal ganglia
 Areas of grey matter, lying deep within cerebral
hemispheres, with connection to the cerebral cortex and
thalamus.
 Part of extra-pyramidal tracts and are involved in initiation
and fine control of complex movement and learned
coordinated activities.
 If control is inadequate or absent movements are jerky,
clumsy and uncoordinated.

21. HYPOTHALAMUS
 -situated below and infront of the thalamus,
immediately above the pituitary gland.
 Linked to anterior lobe of pituitary gland by blood
vessels and posterior by nerve fibers and controls the
output of various hormones.
 Other functions are:
 The autonomic nervous system
 Appetite and satiety
 Body temperature
 Emotional reactions
 Sexual behaviour
 Circadian rhythm (cycles of sleep and wake)

22. Brain Stem
MIDBRAIN
 Midbrain is the area of
the brain situated
around the cerebral
aqueduct between the
cerebrum above and
the pons below.
 Contains nuclei and
nerve fibres (tracts),
which connect the
cerebrum with lower
parts of the brain with
the spinal cord.

24. PONS
 The pons is situated in front of the cerebellum,
below the midbrain and above the medulla
oblongata.
 Consists mainly of nerve fibres (white matter) that
form a bridge between two cerebellar
hemispheres. And of fibres passing between the
higher levels of the brain and spinal cord
 It also consists of pneumotaxic and apnoustic
centres that operate in conjunction with the
respiratory centre in medulla oblongota
 The anatomical structure of the pons differs from
that of the cerebrum in that the cell bodies(gry
matter) lie deeply and nerve fibres are on surface.

25. Medulla Oblongata
 Extends from pons above and is continous with the
spinal cord below
 2.5 cm long and lies within the cranium.
 The vital centres, consisting of groups of cells (nuclei)
associated with autonomic reflex activity, in its deeper
structure.These are:
 Cardiovascular centre
 Respiratory centre
 Reflex centres of vomiting, coughing, sneezing and
swallowing.

26. Other features of medulla oblongata
 Decussation of pyramids.
 Sensory decussation
 Cardio-vascular center controls heart rate and
force of contraction and B.P
 Respiratory center controls rate and depth of
respiration.
 Reflex centers of coughing, sneezing and
vomiting

27. CEREBELLUM
 Situated behind the ponsand immediately below
the posterior portion of the cerebrum occupying
posterior cranial fossa
 Ovoid in shape
 It has two hemispheres separated by narrow
median strip known as vermis.
 Grey matter forms the surface of cerebellum and
white matter lies deeply

28. Function of cerebellum
 Concerned with coordination of voluntary
muscular movement.
 Coordinates activities associated with
maintenance of posture, balance and equilibrium.