2. CENTRAL NERVOUS SYSTEM
• CNS consists of brain and spinal cord. Brain is
situated within the cranial cavity and the spinal cord
lies within the vertebral column.
• The adult brain constitutes about one fiftieth of total
body weight and weighs about 1400g in males and
1200g in females.
• BRAIN- gray matter is present around the periphery
and white matter in the centre.
3. BRAIN IS PROTECTED BY.....
1. Bony covering-THE CRANIUM
2. The meninges
3. CSF-in the sub arachnoid space
4. MENINGES
1) DURA MATER-outer endosteal layer and
inner meningeal layer enclosing the cranial
venous sinuses between the two.
2) ARACHNOID-thin,transparent and do not dip
into the sulci.
3) PIA MATER-thin, vascular and closely invests
the brain
5.
6. • Dura mater is called as pachymeninges.
• Arachnoid and pia are togather known as
leptomeninges.
• Meningeal layer of dura mater forms four
folds which divide the cavity into
intercommunicating compartments.
7. Folds of dura..
• Falx cerebri-sickle shaped, separates the right from
the left cerebral hemispheres.
• Tentorium cerebelli-seperates the cerebral
hemispheres from the hind brain and lower part of
midbrain.
• Falx cerebelli-separates the two cerebellar
hemisphere.
• Diagphrama sellae-small horizontal fold.
8. • Superior sagittal sinus lies along the superior
margin of falx cerebri-recieves in its course the
superior cerebral vein.
• Inferior sagittal sinus lies along the inferior
margin of falx cerebri-joins great cerebral vein.
• Straight sinus-lies at the confluence of falx
cerebri and tentorium cerebelli.
9.
10. ARACHNOID MATER
• It provides sheath for the cranial nerves as far
as their exit from the skull.
• Arachnoid villi are small finger like processes
of arachnoid tissue projecting into the venous
sinuses. They absorb CSF. With age these villi
enlarge to form pedunculated tufts called
arachnoid granulations.
11. • EPIDURAL SPACE-between inner surface of
the cranium and dura mater.
• SUBDURAL SPACE-between dura and
arachnoid.
• SUB ARACHNOID SPACE-Between arachnoid
and pia mater,contains CSF, large vessels of
the brain and cranial nerves.
12. • The function of CSF is primarily as a shock
absorber and a cushion for the brain so that it
doesn't move around so much in the head.
• CSF is secreted by specialized cells within the
walls of the ventricles known as choroid
plexus.
• Re-absorption occurs in the subarachnoid
space by venous structures known as
"arachnoid villi"
13.
14. PARTS OF BRAIN
• Developmentally brain consists of
forebrain,midbrain and hindbrain.
Forebrain-cerebrum+diencephalon
Midbrain
Hindbrain-pons,medulla,cerebellum.
16. CEREBRUM
• Longitudinal cerebral fissure-divides it into two
hemispheres.
• Corpus callosum- joins the two hemispheres across the
median plane
• Each cerbral hemisphere consists of
Outer grey matter
Inner white matter
Basal ganglia/basal nuclei
Lateral ventricle.
22. SULCI AND GYRI
• In order to increase the surface area of brain it
is folded at places creating sulci and gyri.
• The grooves that make these wrinkles are
called sulci and the ridges between them are
called gyri.
23. MEDICOLEGAL IMPORTANCE
• In generalised edema of the brain flattening
of the cerebral convulsions with obliteration
of sulci is seen.
• In such cases it is difficult to appreciate the
sulci and gyri correctly.
24. SULCI AND GYRI
• Central sulcus
• Lateral sulcus
• Parieto occipital sulcus
.
25. • CENTRAL SULCUS- begins on the medial
surface and runs on the superolateral sulcus
obliquely downwards and forwardsand ends a
little abive the posterior ramus of the lateral
sulcus
26.
27.
28. • LATERAL SULCUS- inferiorly separates the
orbital and tentorial surfaces,then reaches
superolaterally and divides into anterior,
ascending and posterior rami
29. • PARIETO OCCIPITAL SULCUS-present on the
medial aspect.
• PREOCCIPITAL NOTCH-indentation on the
inferolateral boarder about 5cm in front of
occipital pole.
33. MEDIAL SURFACE OF BRAIN
• Central part of medial suface is occupied by
corpus callosum.
• Below this lies the septum pellucidum, the
fornix and the thalamus.
.
39. • CINGULATE SULCUS-starts in front of the genu
and runs backwards parallel to upper
marginof corpus callosum
• SUPRASPLENIAL SULCUS- lies above and
parallel to splenium.
• CALCARINE SULCUS-begins a little below the
splenium and runs towards occipital pole. It
gives off the parietooccipital sulcus.
40. INFERIOR SURFACE
• Divided into orbital surface and tentorial
surface.
• ORBITAL surface-parallel to medial orbital
boarder there is olfatory sulcus. The rest of
the orbital surface is divided by an ‘H’ shaped
sulcus.
42. • Part medial to collateral sulcus is
parahippocampal gyrus.
• Part lateral to collateral sulcus is divided into
medial and lateral occipitotemporal gyri by
the occipitotemporal sulcus.
46. BASAL GANGLIA
• Large subcortical masses of gray matter
located within the white matter in the basal
part of cerebral hemisphere.
• Functionally it includes substantia nigra, red
nucleus and subthalamus.
49. • Caudate nucleus has a head, body and a tail.
• Lentiform nucleus-lateral surface,medial
surface,inferior surface.
• Amygdaloid body-nuclear mass in the
temporal lobe and is continuous with the tail
of caudate nucleus.
• Claustrum-saucer shaped nucleus between
the putamen and insula
50. • Corpus stritum is divided by internal capsule into
caudate nucleus and lentiform nucleus.
• Lentiform nucleus is divided into a lateral part
putamen and a medial part called globus
pallidus.
• Caudate nucleus and putamen are togather
known as striatum whereas globus pallidus is the
pallidum.
51. FUNCTIONS
• Corpus striatum regulates muscle tone and
help in smoothening voluntary movements.
• It controls automatic associated movements
and the coordinated movements of different
parts of the body for emotional expression.
52. INTERNAL CAPSULE
• Large band of fibres situated in the
inferomedial part of cerebral hemisphere.
• In horizontal sections of brain it appears V
shaped with its concavity directed laterally.
• It consists of fibres going from and to the
cerebral cortex.
55. • Anterior limb-between head of caudate
nucleus and lentiform nucleus.
• Posterior limb-between thalamus and
lentiform nucleus.
• Genu-bend between anterior and posterior
limbs.
• Retrolentiform part-lies behind the lentiform
nucleus.
• Sublentiform part-below the lentiform
nucleus.
56. DIENCEPHALON
• Is a middle structure which is embedded in the
cerebrum.
1. Thalamus
2. Hypothalamus
3. Metathalamus
4. Epithalamus
5. Subthalamus.
57. THALAMUS
• Large ovoid mass of grey matter above the
midbrain.
• Largest part of diencephalon.
• Thalami on both sides are separated by the
cavity of the 3rd ventricle.
58.
59. HYPOTHALAMUS
• Most inferior part of diencephalon and
contains several small nuclei and tracts.
• Mamillary bodies appear as rounded
elevations on the base of the brain in the
region of interpeduncular fossa.
60. METATHALAMUS
• Consists of two rounded medial and lateral
geniculate bodies which protrude from
posterior inferior surface of thalamus.
62. SUBTHALAMUS
• Small area that lies between thalamus and
mid brain.
• It contains several nerve tracts and
subthalamic nuclei which are associated with
basal ganglia.
63.
64. LIMBIC SYSTEM
• The limbic system is a complex set of
structures that lies on both sides of the
thalamus, just under the cerebrum.
• It includes the hypothalamus, the
hippocampus, the amygdala, and several
other nearby areas.
65.
66. • It appears to be primarily responsible for our
emotional life, and has a lot to do with the
formation of memories.
• HIPPOCAMPUS- is concerned with long term
memories.
69. MIDBRAIN
• Connects forebrain with the hind brain.
• Cavity is called cerebral aqueduct,connects
third ventricle with the fourth ventricle.
70. TRANVERSE SECTION THROUGH
MIDBRAIN
• Tectum is the part posterior to aqueduct.
• Each half of the midbrain anterior to aqueduct is
called cerebral peduncle.
• Each cerebral peduncle is divided into;
a) CRUS CEREBRI-anteriorly
b) SUBSTANTIA NIGRA-middle
c) TEGMENTUM-posteriorly
71. • Medial and lateral geniculate bodies are
situated in the posterior apect of midbrain.
• Superior colliculus is connected to lateral
geniculate body by the superior brachium,
inferior colliculus is connected to medial
geniculate body by the inferior brachium.
72.
73. PONS
• Large middle part of brainstem.
• Has two surfaces 1. ventral 2.dorsal.
• Dorsal surface is hidden by the cerebellum,
and forms the upper half of the floor of fourth
ventricle.
74. VENTRAL SURFACE
• Ventral surface is convex towards both sides
and is transversely striated.
• In the median plane it is shows a vertical
basilar sulcus which lodges the basilar artery.
• Laterally the surface is continuous with the
middle cerebellar peduncle.
75. • Trigeminal nerve is attached to this surface at
the junction of pons with the peduncle.
• Abducent, facial and vestibulocochlear nerves
are attached to the lower boarder.
76.
77. MEDULLA
• Lies in the anterior part of posterior cranial fossa
extending down to the foramen magnum.
• Medulla is divided into right and left halves by
the anterior and posterior median fissures.
• Each half is divided into anterior,lateral and
posterior regions by anterolateral and
posterolateral sulci.
78. • Anterior region is in the form of an elevation
called the pyramid.
• Upper part of the lateral region shows an oval
elevation- the olive.
• The rootlets of hypoglossal nerve emerge
from the anterolateral sulcus between the
pyramid and the olive.
79. • Rootlets of 9th 10th and of the cranial part of
accessory nerve emerge through the
posterolateral fissure.
• Upper part of the posterolateral region shows
a V shaped depression which is the lower part
of floor of fourth ventricle.
80. • Below the floor three elevations are seen:
fasciculus gracillis, fasciculuc cuneatus and
inferior cerebellar peduncle.
• Upper ends of fasciculus gracillis and
fasciculus cuneatus expands to form the
gracile and cuneate tubercles.
81. • In the lower part of medulla there is another
elevation called tubercinerium produced by
spinal nucleus of trigeminal nerve.
• Medulla is divided into two parts, the lower
closed part with a central canal; upper open
part where central canal opens out to form
the fourth ventricle.
82.
83. CEREBELLUM
• Largest part of hind brain.
• Grey matter is highly folded and the
arrangement is called “arbor vitae”(vital tree
of life)
84. • Consists of two cerebellar hemispheres united
to each ither through a median vermis.
• Superior surface is convex, the two
hemispheres are continuous.
• Inferior surface has a notch called vallecula
that separates the two hemispheres.
85.
86.
87.
88. Each hemisphere is divided into three lobes
1. Anterior lobe-lies on the anterior part of
superior surface.
2. Middle lobe-largest
3. Flocculonodular lobe-smallest.
89. • Middle lobe is limited in front by the fissura
prima and by the posterolateral fissure on the
inferior surface.
• Cerebellum is divided into numerous small
parts by fissures.
90. • Horizontal fissure-separates superior surface
from the inferior.
• Fissura prima-separates anterior lobe from the
middle lobe on the superior surface.
• Posterolateral fissure- separates middle lobe
from the flocculonodular lobe on the inferior
surface.
91. VENTRICLES OF BRAIN
• LATERAL VENTRICLES- irregular cavities
situated on each cerebral hemisphere.
• Each communicate with the third through an
interventricular foramen(foramen of Monroe).
• Ech lateral ventricle has;
Central part
Three horns-anterior, posterior, inferior.
92.
93. THIRD VENTRICLE
• Median cleft between the two thalami.
• Developmentally it represents the cavity of
the diencephalon.
• Posteriorly it communicates with the fourth
ventricle through cerebral aqueduct.
94. THE FOURTH VENTRICLE
• Last and lowest ventricle of cerebrum.
• Tent shaped.
• Its roof contains three apertures for the
closely guarded release of CSF into the sub
arachnoid space.
95. • Dorsally on the lower part of the roof there is
a median aperture-foramen of Magendie.
• On either sides it communicates with the
subarachnoid space through lateral apertures-
foramina of Luchka.
96.
97. CIRCLE 0F WILLIS
• Provides important communication between
blood supply of forebrain and midbrain.
• Internal carotid artery (ICA) enters the cranial
cavity bilaterally and divides into the Anterior
cerebral artery (ACA) and Middle cerebral
artery (MCA).
98. • The anterior cerebral arteries are then united
by an anterior communicating (ACOM) artery.
• Posteriorly, the basilar artery, formed by the
left and right vertebral arteries, branches into
a left and right Posterior cerebral artery(PCA),
forming the posterior circulation.
• The PCAs complete the circle of Willis by
joining the internal carotid system anteriorly
via the posterior communicating (PCOM)
arteries.
