Objective of the Study: Anatomy and Functions of different parts of the Brain and Spinal Cord.

1. Central Nervous System Anatomy and Functions.
PROF ABHIJEET BHATTACHARYA

2. Brain organization
The brain and spinal cord develop from the
ectodermal neural tube. The anterior part of the
neural tube expands and later constricts into three
regions:-
➢ Prosencephalon
➢ Mesencephalon
➢ Rhombencephalon
Prosencephalon or Fore brain subdivide into
Telencephalon and Diencephalon.
Rhombencephalon or Hind brain subdivide into
Metencephalon and Myelencephalon.

3. Brain organization
 Telencephalon develop into Cerebrum and lateral ventricles.
 Diencephalon develops into Thalamus, Hypothalamas
,Epithalamus and third ventricle.
 Mesencephalon give rise to midbrain and Cerebral Aqueduct.
 Metencephalon give rise to Pons, Cerebellum and upper part
of the fourth ventricle.
 Myelencephalon give rise to Medulla oblongata and lower
part of the fourth ventricle.

4. CENTRAL
NERVOUS
SYSTEM
BRAIN

5. Brain
Major Parts of
the Brain:-
➢Cerebrum
➢Brain Stem
➢Cerebellum
➢Diencephalon

6. Cerebrum

7. Cerebral Hemisphere Contd…
 Cerebrum is the upper most part of the brain.
 It is the largest part of the brain (2/3rd of the total weight)
 It contains two hemispheres divided by a sagittal fissure called
longitudinal cerebral fissure.
 Cerebral hemisphere has inner core of myelinated nerve fibers,
white mater and outer cortex of grey mater.
 A thick band of white matter connects internally the two
hemispheres, called the corpus callosum.
 Gyri are the folds in the cerebral cortex and sulci are the grooves.
 The cortex contains 16 billion neurons.

8. Lobes of Cerebral hemisphere
Each cerebral hemisphere further subdivided into lobes:-
➢ Frontal
➢ Parietal
➢ Temporal
➢ Occipital lobes
➢ The central sulcus separates the frontal lobe from the parietal lobe.
➢ The lateral cerebral sulcus separates the frontal lobe from the
temporal lobe.
➢ The parieto-occipital sulcus separates the parietal lobe from the
occipital lobe.

9. Cerebral White Matter
Cerebral White Matter:- The cerebral white matter
consists primarily of myelinated axons in three types
of tracts
➢ Association tracts
➢ Commissural tracts.
➢ Projection tracts

10. Basal Nuclei
Deep within each cerebral hemisphere are three nuclei
(masses of gray mater) that are collectively termed the
basal nuclei or basal ganglion. The three nuclei are globus
pallidus, putamen and caudate nucleus.
➢ The basal nuclei receive input from the cerebral cortex
and provide output to motor parts of the cortex via the
medial and ventral group nuclei of the thalamus.
➢ A major function of the basal nuclei is to help regulate
initiation and termination of movements.

11. Functional Organization of the
Cerebral Cortex
➢ Specific types of sensory, motor, and integrative signals are
processed in certain regions of the cerebral cortex
➢ Sensory Areas Sensory impulses arrive mainly in the posterior
half of both cerebral hemispheres, in regions behind the central
sulci.
➢ The primary somatosensory area is located directly posterior to
the central sulcus of each cerebral hemisphere in the
postcentral gyrus of each parietal lobe.

12. Motor Areas.
Motor Areas:-Motor output from the cerebral cortex flows
mainly from the anterior part of each hemisphere.
➢ The primary motor area is located in the precentral gyrus
of the frontal lobe.
➢ Each region within the area controls voluntary
contractions of specific muscles or groups of muscles.
➢ Broca’s speech area is located in the frontal lobe close
to the lateral cerebral sulcus.
➢ Speaking and understanding of language are complex
activities , speaking is controlled by the Broca’s area.

13. Association Areas (Connected with one another by
association tracts)
➢ The somatosensory
association area
➢ The visual association area
➢ The facial recognition area
➢ The orbitofrontal cortex
(odor)
➢ The auditory association
area
➢ Wernicke’s area
(understanding language)
➢ The prefrontal cortex
(personality, intelligence)
➢ The frontal eye field area

14. The Brain Stem
The brain stem is the part of the brain between the
spinal cord and the diencephalon. It consists of
three structures:-
➢ Medulla oblongata
➢ Pons
➢ Midbrain.

15. Medulla oblongata
➢ The medulla oblongata is continuous with the superior part of the
spinal cord; it forms the inferior part of the brain stem.
➢ The medulla begins at the foramen magnum and extends to the
inferior border of the pons, a size of about 3 cm.
➢ The medulla’s white matter contains all sensory tracts and motor
tracts. Some white matter forms bulges called pyramids.
➢ Medulla contains several nuclei controlling vital body functions,
like cardio-vascular center and respiratory center. Also contains
reflex centers for sneezing , coughing , vomiting & deglutition.

16. Pons
➢ The pons lies directly superior to the medulla and anterior to
the cerebellum and is about 2.5 cm long.
➢ The pons consists of both nuclei and tracts.
➢ The pons is a bridge that connects parts of the brain with one
another.
➢ The ventral region of the pons forms a large synaptic relay
station consisting of scattered gray centers called pontine
nuclei. This region is responsible for coordination and
maximizing the efficiency of voluntary motor output.

17. Midbrain
➢ The midbrain or mesencephalon extends from the pons to
the diencephalon and is about 2.5 cm long.
➢ The aqueduct of the midbrain connects the third ventricle
with the fourth ventricle.
➢ The anterior part of the midbrain contains paired bundles of
axons known as the cerebral peduncles.
➢ The posterior part of the midbrain, called the tectum,
contains four rounded elevations. Two superior colliculi,
serve as reflex centers for certain visual activities. The two
inferior colliculi, are part of the auditory pathway.
➢ The midbrain contains several other nuclei, including the left
and right substantia nigra.

18. Cerebellum
➢ The cerebellum, occupies the inferior and
posterior part of the cranial cavity.
➢ The cerebellum has a highly folded surface that
greatly increases the surface area of its outer
gray matter cortex.
➢ One tenth of brain mass but nearly half of the
neurons.
➢ The cerebellum is posterior to the medulla and
pons and inferior to the posterior portion of the
cerebrum
➢ The central constricted area is the vermis, and
the lateral “wings” or lobes are the cerebellar
hemispheres.

19. Cerebellum
➢ The outer layer of the cerebellum, called the cerebellar cortex, consists
of gray matter in a series of slender, parallel folds called folia.
➢ Below gray matter there are tracts of white matter called arbor-vitae.
Deeper, within the white matter, are regions of gray matter the
cerebellar nuclei.
➢ Cerebellum evaluate how well movements initiated by motor areas in
the cerebrum are Association areas are connected with one another by
association tracts
➢ actually being carried out. It sends feedback to the motor area of
cerebral cortex via thalamus.
➢ Main brain region that regulates posture and balance.

20. Diencephalon
➢ The diencephalon forms a central
core of brain tissue just superior to
the midbrain.
➢ Almost surrounded by Cerebral
hemisphere.
➢ Extends from the brain stem to the
Cerebrum.
➢ Surround the third ventricle.
➢ It includes Thalamus, Hypothalamus
and Epithalamus.

21. Thalamus
➢ The Thalamus measures about 3 cm in length and makes up 80% of the
diencephalon.
➢ Consists of paired oval masses of gray matter organized into nuclei with
interspersed tracts of white matter.
➢ The Thalamus is the major relay station for most sensory impulses that reach
the primary sensory areas of the cerebral cortex from the spinal cord and
brain stem.
➢ The Thalamus contributes to motor functions by transmitting information
from the cerebellum and basal nuclei to the primary motor area of the
cerebral cortex.
➢ Relays nerve impulses between different areas of the cerebrum and plays a
role in the maintenance of consciousness.

22. Hypothalamus
The hypothalamus is a small part of the diencephalon
located inferior to the thalamus.
There are four regions of hypothalamus:-
➢ The mammillary region
➢ The tuberal region
➢ The supraoptic region
➢ The Preoptic region

23. Hypothalamus Functions
➢ Major regulators of homeostasis.
➢ Sensory impulses related to both
somatic and visceral senses arrive
at the hypothalamus.
➢ Impulses from receptors for vision,
taste, smell, blood glucose
concentration, blood temperature,
osmotic pressure arrive at the
hypothalamus.
➢ Hypothalamus produces many
important hormones like,
TSH,GNRH, CRH , somatostatin,
Oxytocin and ADH.
➢ Regulates emotional and behavioral
pattern.
➢ Contains Feeding center, Satiety
Center and thirst center.
➢ Controls body temperature, it act as
the thermostat.
➢ SCN ( Suprachiasmatic Nucleus)
Regulates Circadian rhythm

24. Epithalamus
➢ The epithalamus, a small region superior and posterior to the
thalamus, consists of the pineal gland and habenular nuclei.
➢ The pineal gland is about the size of a small pea.
➢ The pineal gland secretes the hormone melatonin. Promotes
sleep.
➢ The habenular nuclei are involved in olfaction, especially
emotional responses to odors.

25. CENTRAL
NERVOUS
SYSTEM
SPINAL CORD

26. Spinal Cord
The spinal cord is located within the
vertebral canal of the vertebral column.
The meninges are three protective,
connective tissue coverings that
encircle the spinal cord and brain.
From outer to inner they are:-
➢ dura mater
➢ arachnoid mater
➢ pia mater.

27. Spinal Cord Contd…..
➢ Extends from foramen magnum to second lumbar vertebra in adult.
➢ Segmented:- Cervical – Thoracic – Lumbar – Sacral
➢ Connected to 31 pairs of spinal nerves
➢ All are mixed nerves; I.e., contain both sensory and motor fibers
➢ Not uniform in diameter throughout length – Cervical & Lumbar
enlargement
➢ Conus medullaris: Tapered posterior end.
➢ Cauda equina: Origins of spinal nerves extending inferiorly from
lumbosacral enlargement and conus medullaris.

28. Spinal Cord TS

29. Spinal Cord Contd…
➢ Transverse section of the spinal cord shows regions of white matter
that surround an inner core of gray matter.
➢ Two grooves penetrate the white matter of the spinal cord and divide it
into right and left sides.
➢ The gray matter of the spinal cord is shaped like the letter H or a
butterfly; it consists of dendrites and cell bodies of neurons,
unmyelinated axons, and neuroglia.
➢ The gray commissure forms the crossbar of the H. In the center of the
gray commissure is a small space called the central canal.
➢ The gray matter on each side of the spinal cord is subdivided into
regions called horns.

30. Spinal Cord Contd….
The posterior (dorsal) gray horns contain cell bodies and axons of interneurons.
➢ The posterior (dorsal) gray horns contain cell bodies and axons of interneurons.
➢ The anterior (ventral) gray horns contain somatic motor nuclei, which are
clusters of cell bodies of somatic motor neurons that provide nerve impulses for
contraction of skeletal muscles.
➢ Between the posterior and anterior gray horns are the lateral gray horns, which
are present only in thoracic and upper lumbar segments of the spinal cord.
➢ The anterior and posterior gray horns divide the white matter on each side into
three broad areas called columns: anterior white columns, posterior white
columns, and lateral white columns

31. Spinal Cord Contd….
➢ Gray horns contain somatic motor nuclei, which are clusters of cell
bodies of somatic motor neurons that provide nerve impulses for
contraction of skeletal muscles.
➢ Between the posterior and anterior gray horns are the lateral gray horns,
which are present only in thoracic and upper lumbar segments of the
spinal cord.
➢ The anterior and posterior gray horns divide the white matter on each
side into three broad areas called columns: anterior (ventral) white
columns, posterior (dorsal) white columns, and lateral white columns

32. Functions of Spinal Cord
The spinal cord has two principal functions in maintaining
homeostasis:
1)Nerve impulse propagation.
➢ The white matter tracts in the spinal cord are highways for nerve
impulse propagation.
➢ The gray matter of the spinal cord receives and integrates
incoming and outgoing information.
2) Integrating center for some reflexes. Reflexes originating from
spinal cord are called Spinal reflexes.

33. Acknowledgement:-
Principles of Anatomy & Physiology.
Gerard J. Tortora / Bryan Derrickson