Gross and salient features of Brain

GROSS & SALIENT
FEATURES OF BRAIN
DR. RAHILA BANU. M.
1st Year MDS.
Dept. of Oral & Maxillofacial Surgery.

CONTENTS
INTRODUCTION
PARTS OF BRAIN
FOREBRAIN (Prosencephalon)
 CEREBRUM
 THALAMENCEPHALON
MIDBRAIN (Mesencephalon)
HINDBRAIN (Rhombencephalon)
 MEDULLA OBLONGATA
 PONS

BRAIN STEM
MEDULLA OBLONGATA
PONS
BLOOD SUPPLY OF BRAIN
CEREBROSPINAL FLUID
BRAIN DISORDERS
SPINAL CORD
BLOOD SUPPLY OF SPINAL CORD
VENOUS SUPPLY OF SPINAL CORD
SOME NEURAL PATHWAYS
REFERENCES

INTRODUCTION
Human nervous system is responsible for judgement,
intelligent and memory.
Nervous system is the chief controlling and
coordinating system of the body.
The sensory part of the nervous system collects
information from surroundings and helps in gaining
knowledge and experience, whereas the motor part is
responsible for responses of the body.

PARTS OF THE NERVOUS SYSTEM
 Two parts:
Central nervous system(CNS) :
 Brain - occupies cranial cavity.
 Spinal cord - occupies upper two-thirds of the
vertebral canal.
Peripheral nervous system :
 Somatic (cerebrospinal) nervous system -
made up of 12 pairs of cranial nerves and 31
pairs of spinal nerves.
 Autonomic nervous system – consists of
sympathetic and parasympathetic nerves.

The human brain is the central organ of the
human nervous system, and with the spinal
cord makes up the central nervous system.
Brain occupies in cranial cavity.

PARTS OF BRAIN
PARTS SUBDIVISION
1 FOREBRAIN
(Prosencephalon)
a) Cerebrum (Telencephalon)
b) Diencephalon (Thalamencephalon)
c) Thalamus
d) Hypothalamus
e) Metathalamus
f) Epithalamus
g) Sub thalamus
2 MIDBRAIN
(Mesencephalon)
a) Tectum
b) Tegmentum
3 HINDBRAIN
(Rhombencephalon)
a) Metencephalon (Pons & cerebellum).
b) Myelencephalon (medulla oblongata)

CEREBRUM
Made up of two cerebral
hemispheres which are
incompletely separated from
each other by the median
longitudinal fissure.
The two hemispheres are
connected to each other by
corpus callosum.
Each hemisphere contains
cavity, called the lateral
ventricle, which contains CSF.
Each hemisphere contains 3
surfaces, 4 borders and 3
poles.

3 Surfaces : superolateral, medial and inferior
surfaces.
a) Superolateral surface: is convex and is related to
the cranial vault.

b) Medial surface: is flat and vertical surface. It is
separated from the corresponding surface of the
opposite hemisphere by falx cerebri and the
longitudinal fissure.

c) Inferior surface: is
irregular surface.
 Divided into
 Anterior part
(orbital surface)
 Posterior part
(tentorial surface).
 The two parts are
separated by a deep
cleft called stem of
the lateral sulcus.

4 Borders :
a) Superomedial Border :
separates the superolateral
surface from the medial
surface.
b) Inferolateral Border :
separates the superolateral
surface from the inferior
surface.
c) Medial Orbital Border :
separates the medial surface
from the orbital surface.
d) Medial Occipital Border :
separates the medial surface
from the tentorial surface.
Coronal section of cerebrum

 3 Poles :
a) Frontal Pole : at the
anterior end.
b) Occipital Pole : at the
posterior end.
c) Temporal Pole : at the
anterior end of the
temporal lobe.

LOBES OF BRAIN
4 Lobes :
a) Frontal
b) Parietal
c) Occipital
d) Temporal
Their positions correspond, very
roughly, to that of the
corresponding bones.

CEREBRAL SULCI & GYRI
 Cerebral cortex is folded into
gyri which are separated from
each other by sulci. This
pattern increases the surface
area.
 In human brain , the total area
of the cortex is estimated to
be more than 2000cm2, and
approximately two-thirds of
this area is hidden from the
surface with in the sulci.
Gyri Sulcus

 Central sulcus : begins at the
Superomedial border of
hemisphere a little behind
the midpoint between the
frontal and occipital poles.
 Lateral sulcus : separates
the orbital and tentorial part
of the inferior surface.
 Parieto-occipital sulcus : is a
sulcus of the medial surface.
 Preoccipital notch : on the
Inferolateral border, about
5mm in front of the occipital
pole.

MAIN FUNCTIONAL AREA OF
CEREBRAL CORTEX
Cerebral cortex has been divided into 52 functional
area by Brodmann (1909).
Typical cortical areas are,
 Motor Areas
 Sensory Areas
 Association Areas

BROCA’S AREA
Also called Anterior Speech
Area.
Area located in the frontal lobe
of the left hemisphere only.
Broca's area is made up of
Brodmann’s areas 44 (pars
opercularis) & 45 (pars
triangularis) of the inferior
frontal gyrus.
Function is speech production.

Blood Supply: Superior division of middle cerebral
artery supplies latero-inferior frontal lobe (location of
Broca's area i.e. language expression).

 Clinical Significances :
 Broca’s Aphasia : partial loss of
the ability to produce language as
a result of brain damage.
 MRI findings : Lesions to Broca's
area can cause temporary speech
disruption, they do not result in
severe speech arrest.

WERNICKE’S AREAS
 Also called Posterior Speech
Area (Area 22).
 It is one of the two parts of the
cerebral cortex that are linked
to speech (other is Broca's
area).
 located in the temporal lobe on
the left side of the brain and is
responsible for the
understanding of speech,
while Broca's area is related to
the production of speech.

Blood Supply: Inferior division of middle cerebral artery
supplies lateral temporal lobe (location of Wernicke's
area i.e. language comprehension).

 Clinical Significances :
 Lesions or damage in the middle
of the left side of the brain
causes Wernicke’s aphasia.
 Stroke is one potential cause of
this condition because it impairs
blood flow to the brain.
 Conditions that may affect
Wernicke’s area of the brain
include head trauma, tumours,
infections, neurological
disorders.
 Diagnosed by MRI or CT scan.

FUNCTIONAL AREAS OF FRONTAL LOBE
1) Primary motor area (Area 4) (to
generate neural impulses that
control the execution of
movements).
2) Premotor area (Area 6)
(performance of voluntary motor
activities)
3) Supplementary motor area
4) Frontal eye field- Area 8.
(control of visual attention and eye
movements)
5) Motor speech area of Broca
(Area 44 & 45) (speech area).
6) Pre frontal cortex (Area 9, 10,
11 & 12). (individual’s personality)

FUNCTIONAL AREAS OF PARIETAL LOBE
 Primary Sensory Area (Area 3,1,2)
(Pain, touch, temperature).
 Secondary Sensory Area (Pain).
 Sensory Association Area (Area 5,7)
(Ability to recognize the object placed
in his / her hand without seeing).
 Sensory Speech Area of Wernicke
(Area 39,40) (concerned with the
interpretation of language through
visual & auditory input).
 Primary Auditory Area ( Area 41,42)
(reception of isolated impressions of
sound, quality & pitch of the sound).

 The occipital lobe is divided into
several functional visual areas.
 The first functional area is the
primary visual cortex. It contains a
low-level description of the local
orientation and colour properties
within small receptive fields.
 Primary visual cortex projects to
the occipital areas of the ventral
stream (visual area V2 and visual
area V4), and the occipital areas of
the dorsal stream (visual area V3,
visual area MT (V5), and the
dorsomedial area (DM)).
FUNCTIONAL AREAS OF OCCIPITAL LOBE

FUNCTIONAL AREAS OF TEMPORAL LOBE
 The temporal lobe holds the
primary auditory cortex, which is
important for the processing of
both speech and vision in humans.
 Functional Areas :
 Audito Sensory Area (Area 41.42).
 Audito psychic area (Area 22).
 Sensory speech (Wernicke's) area
(Area 39, 40).

DIENCEPHALON
It is a middle
structure which is
largely embedded
in the cerebrum, &
therefore hidden
from surface view.

Dorsal part divided into 3
parts:
Thalamus (dorsal
thalamus)
Metathalamus
Epithalamus
Ventral part divided into 2
parts:
Hypothalamus
Sub thalamus (ventral
thalamus)

THALAMUS
 Is a large mass of grey matter situated in the lateral
wall of the 3rd ventricle & in the floor of the central
part of lateral ventricle.
 Without thalamus, the brain cannot diagnose the
sensory information transmitted to it.

It has : anterior and
posterior ends ; superior,
inferior, medial & lateral
surfaces.
Anterior end : forms the
posterior boundary of
interventricular foramen.
Posterior end (pulvinar) :
overhangs the lateral and
medial geniculate bodies,
and the superior colliculus
with its brachium.

Sup. Surface : divided
into lateral ventricular
part & medial extra
ventricular part.
Inf. Surface : rest of
sub thalamus and
hypothalamus.
Medial surface : forms
posterosuperior part
of the lateral wall of
3rd ventricle.
Lateral surface : forms
medial boundary of
posterior limb of
internal capsule.

Also called mesencephalon.
Connect hindbrain with the forebrain.
The mesencephalon is considered part of the
brainstem.
Midbrain passes through the tentorial notch.

The midbrain serves important functions in motor
movement, particularly movements of the eye, and in
auditory and visual processing.

 Also called rhombencephalon.
 The lower part of the brainstem, comprising the
cerebellum, pons, and medulla oblongata.
 An area of the brain that coordinates information
coming into and out of the spinal cord, and controls
the basic functions of life. (reflex centres of heart &
respiratory rates, coughing, swallowing, vomiting
etc).

BRAIN STEM
 Connects the spinal cord to cerebrum.
 Various ascending & descending tracts pass through
the 3 components of the brain stem.
 Consists of –
 medulla oblongata
 Pons
 midbrain

MEDULLA OBLONGATA
 Lowest part of the brain stem,
where it is continuous with
the spinal cord.
 It lies in the anterior part of
the posterior cranial fossa,
extending down to foramen
magnum.

External features :
 The medulla is divided
into right & left halves by
anterior and posterior
median fissures.
 Each halves further
divided into anterior,
lateral & posterior region
by the antero lateral &
postero lateral sulci.

 Ant.region – in the form of
longitudinal elevation
called pyramid. (pyramid is
made up of cortico spinal
fibres.
 The upper part lateral
region shows an oval
elevation called olive.
 The rootlets of the
hypoglossal nerve emerges
from the anterolateral
sulcus between the
pyramid & olive.

 The rootlets of cranial nerve IX
& X (ie, glossopharyngeal &
vagus nerve) and of the
accessory nerve emerges
through the posterolateral
fissure, behind the olive.
 In the lower part of the
medulla there is another
elevation called tubercinerium.

 Medulla is divided in 2 parts :
Lower closed part with a central canal.
Upper open part where the central canal
opens out to form the 4th ventricle.

Functions of medulla oblongata
It controls the Autonomic Nervous System (ANS
control).
It regulates the blood vessel dilation to reduce or
increase the flow of oxygen and respond to the heart
functions.
It regulates the digestive system and maintains the
levels of digestion within the body.
Maintaining the coordination between various body
movements.

It controls the respiratory and cardiovascular
activities in the body.
It looks after the blood pressure, regulates heart
rate, and check the respiratory rate.
All kinds of involuntary reflexes, like sneezing,
swallowing, and gag reflexes are controlled and
regulated by Medulla Oblongata.
Controls the voluntary movements of the body
(under conscious control such as exercising,
moving arms, kicking a ball or lifting a weight etc.)

Disorders of Medulla Oblongata
 Medulla is responsible for controlling various
autonomic functions in the body, like heart
contraction, breathing, and more. So, any damage to
it can be causes to the brain and result in the death of
a person.
 Major complication is “medullar abscess” :- a
condition of rapidly progressive numerous cranial
nerve clusters and diminished levels of consciousness.

 Any damages or injuries in Medulla Oblongata may
result in various sensory problems. (like numbness, lack
of control over the movement of various body organs,
difficulty swallowing the food, and even paralysis.)
 The multiple system atrophy is a major neurological
disorder that damages the nerves cells specified within
the brain areas including the medulla oblongata. This
can result in loss of control over various autonomic
diseases (like coordination, bladder control).

PONS
Middle part of the
brainstem, connecting
the midbrain with the
medulla.

 External features of pons:
Have 2 surfaces – ventral &
dorsal.
Ventral (anterior) surface : is
convex in both directions.
Trigeminal (cranial V) nerve
is attached to this surface at
the junction of pons with the
peduncle.
The abducent, facial &
vestibulo-cochlear nerves are
attached at the lower border
of the ventral surface.

Dorsal (posterior) surface :
is hidden by cerebellum, &
forms upper half of the
floor of the 4th ventricle.

Internal features of pons :
In transverse section, divided into ventral & dorsal
parts.
ventral (basilar) part : is continuous inferiorly with
the pyramids of medulla.

The dorsal (tegmental) part :
is a direct upward
continuation of the medulla
(excluding the pyramid).

CERBROSPINAL FLUID
 Cerebrospinal fluid is a
modified tissue fluid.
 It is contained in
ventricular system of
the brain & in the
subarachnoid space
around the brain &
spinal cord.

Formation :
 The bulk of CSF is formed by the choroid plexuses of
the lateral ventricle, and lesser amounts by choroid
plexuses of the 3rd & 4th ventricle.
 Also formed by the capillaries on the surface of the
brain and spinal cord.
 Total quantity of CSF – 125 - 150 ml
 It is formed at the rate of about 200 ml /hour or
5000 ml/day.

Circulation of CSF :
CSF passes from each lateral ventricle to 3rd ventricle
through the interventricular foramen.
From 3rd ventricle it passes to 4th ventricle through
the cerebral aqueduct.
From here the CSF passes to the sub arachnoid space
through the median & lateral apertures of 4th
ventricle.

Absorption of CSF :
Absorbed chiefly through the arachnoid villi and
granulations, & is drained into the cranial venous
sinuses.
Also absorbed partly by perineural lymphatics around
the 1st (olfactory), 2nd (optic), 8th (vestibulo-cochlear)
cranial nerves.
Also absorbed by veins related to spinal nerves.

Functions of CSF :
Protects brain and spinal cord from trauma.
Supplies nutrients to nervous system tissue.
Removes waste products from cerebral
metabolism.

BLOOD SUPPLY OF THE BRAIN
 Cerebral circulation is the movement of blood
through the cerebral arteries and veins supplying
the brain.
 The rate of the cerebral blood flow in the adult is
typically 750 millilitres per minute, representing
15% of the cardiac output.

BLOOD SUPPLY :
 Blood supply to the brain is
normally divided into anterior
and posterior segments.
 The circle of Willis is formed
by two group of arteries - the
internal carotid arteries and
two vertebral arteries. These
arteries provide the anterior
and posterior circulation of
the brain respectively.

 The anterior and posterior cerebral circulations
are interconnected via bilateral posterior
communicating arteries.
 They are part of the Circle of Willis, which
provides backup circulation to the brain.

 The Circle of Willis is a part of the
cerebral circulation & is composed of
:
 Anterior cerebral artery (L&R)
 Anterior communicating artery
(connects two anterior cerebral
artery)
 Internal carotid artery (L&R)
(arises from common carotid
artery)
 Posterior cerebral artery(L&R)
(arises from the basilar artery)
 Posterior communicating
artery (L&R) (branch of the
internal carotid artery)
 The middle cerebral arteries
supplying the brain, are not
considered part of the circle.

Clinical significance :
• Sub arachnoid haemorrhage : Is
bleeding into the subarachnoid
space.
• Subclavian steal syndrome : In
this syndrome, blood is stolen
from the circle of Willis to
preserve blood flow to the upper
limb. Subclavian steal syndrome
results from a proximal stenosis
(narrowing) of the Subclavian
artery.

CEREBRAL HEAMORRHAGE
 Cerebral haemorrhage is a type of
intracranial bleed that occurs
within the brain tissue or
ventricles.
 Symptoms :
 Headache
 Fever
 One-sided weakness
 Vomiting
 Seizures
 Decreased level of consciousness
 Neck stiffness

Causes :
Brain trauma
Aneurysms (weakness in the wall
of a cerebral artery or vein causes
a localized dilation or ballooning
of the blood vessel)
Brain tumours
Diagnosed by CT scan.
Treatment :
Surgery(required if the
hematoma is greater than 3 cm).
Ventricular drain

TRANSIENT ISCHEMIC ATTACK
 is a brief episode of
neurological dysfunction
caused by loss of blood flow
(ischemia) in the brain, spinal
cord, or retina, without tissue
death (infarction).

 Signs & Symptoms :
 Painless
 Temporary loss of vision
 One-sided facial droop
 Unilateral weakness
 Numbness on one side of
the body.
 Diplopia (double vision)
 Problems with balance
and spatial orientation
 Diagnosed by MRI.

Treatment :
 Antiplatelet medications : such as aspirin.
 Anticoagulant medications : Anticoagulant therapy can
decrease the relative risk of ischemic stroke. Warfarin is
a common anticoagulant used.
 Control Blood Pressure : SBP< 130mmHg & DBP<
90mmHg.
 Control Cholesterol.
 Control Diabetes. (RBS 80 – 160 mg/dl)
 Surgery (carotid endarterectomy): In this, makes an
incision in the neck, opens up the carotid artery, and
removes the plaque occluding the blood vessel.

 Epidural hematoma is when
bleeding occurs between the
duramater and the skull.
 Lucid Interval : is a temporary
improvement in a patient's
condition after a traumatic brain
injury, after which the condition
becoming progressively worse.
 A lucid interval is especially
indicative of an epidural
hematoma.
EPIDURAL HEMATOMA

Symptoms of epidural Hematoma :
 Loss of consciousness
 Head ache
 Confusion
 Vomiting
 Inability to move parts of the body.

 Males are more often affected than females.
 Diagnosis is typically by a CT scan or MRI.
 Treatment is generally by urgent surgery.
(craniotomy or burr hole surgery).
 Without treatment leads to death.

SUBDURAL HEMATOMA
 Subdural hematoma is a
type of hematoma, usually
associated with traumatic
brain injury.
 Blood between the inner
layer of the duramater and
the arachnoid mater.

Signs & Symptoms
 History of recent head injury
 Loss of consciousness
 Seizures
 Pain
 Headache
 Disorientation
 Amnesia
 Weakness
 Personality changes
 Inability to speak
 Difficulty to walk
• Nausea or vomiting
• Loss of muscle control
• Altered breathing patterns
• Hearing problems
• Blurred Vision
• Abnormal movement of the
eyes.

 Diagnosed by CT scan or MRI.
 Treatment depends on its size and
rate of growth.
 Small size can be managed by careful
monitoring until the body heals itself.
 Other small subdural hematomas can
be managed by inserting a temporary
small catheter through a hole drilled
through the skull and sucking out the
hematoma.

 Large / symptomatic hematomas
require a craniotomy, the surgical
opening of the skull.
 Postoperative complications :
 Increased intracranial pressure.
 Brain Edema.
 New or recurrent bleeding.
 Infection.
 Seizure.

SUB ARACHNOID HEMORRHAGE
• Is bleeding into the subarachnoid
space.(Area between the
arachnoid membrane & pia mater
surrounding the brain).
• Symptoms :
• severe headache of rapid onset
• Vomiting
• decreased level of consciousness
• Fever
• sometimes seizures.

 Diagnosed by CT scan.
 Treatment option is
conservative treatment.

INTRAVENTRICULAR HEMORRHAGE
 is a bleeding into the brain's
ventricular system, where the
cerebrospinal fluid is produced
& circulates through towards
the subarachnoid space.
 Symptoms :
 sudden onset of headache
 nausea and vomiting
 Alteration of the mental state
 Focal neurological signs are
either minimal or absent.
 Yellow-tinged CSF

 Diagnosed by CT scan.
 For Extreme cases - an open craniotomy may
be required.

PARKINSON’S DISEASE
 Parkinson's disease is a long-
term degenerative disorder of
the central nervous system
that mainly affects the motor
system.
 signs and symptoms:
 Shaking
 Slowed movement
 Rigid muscles
 balance problems
 Loss of automatic movements
 Speech and writing changes

 Parkinson's disease is accompanied by some additional
problems like Thinking difficulties, Depression and
emotional changes

SPINAL CORD
 Is the lower elongated,
cylindrical part of CNS,
responsible for establishing
contacts between the brain
& peripheral end organs.
 It occupies the upper 2/3rd
of the vertebral canal.
 Gives off 31 pairs of spinal
nerves.

TRACTS OF SPINAL CORD
 A collection of nerve fibres that connects two masses
of gray matter with in the central nervous system is
called a tract.
 They may be ascending or descending tracts.

DESCENDING TRACTS
It have 2 type tracts :
A. Pyramidal or cortico spinal tracts : descends from the
cerebral cortex to spinal cord.
Consists of : lateral cortico spinal tract & anterior
cortico spinal tract.
B. Extrapyramidal tracts :
Rubro spinal tract
Medial & lateral reticulo spinal tracts
Olivo spinal tract
Vestibulo spinal tract
Tecto spinal tract

DESCENDING TRACTS
No. Name Function Spinal
Segment
Beginning 1st
termination
A1 Lateral
cortico
spinal.
(crosse
d)
Main
motor
tract
C1 to S5 Motor
area of
cortex
(upper
neuron)
Anterior grey
column cells
alpha motor
neurons
A2 Ant.
Cortico
spinal.
(uncros
sed)
Main
motor
tract
C1 to S5 Motor
area of
cortex
(upper
motor
neuron)
Anterior grey
column cells
alpha motor
neurons

No Name Function Spinal
Segment
Beginning 1st
termination
B1 Rubro-
spinal.
(crosse
d)
Efferent
pathway
for cere-
bellum &
corpus
stratum
C1 to C5 Red
nucleus of
midbrain
Anterior grey
column cells.
B2 Medial
reticulo
spinal.
(uncros
sed)
Extra
pyramidal
tract
C1 to S5 Reticular
formation
of grey
matter of
pons
Anterior grey
column cells
(inter
neurons).

Segment
Beginning 1st
termination
B3 Lateral
reticulo
spinal.
(crosse
d)
Extra
pyramidal
tract
C1to S5 Reticular
formation
of grey
matter of
medulla
oblongata
Anterior grey
column cells
(inter
neurons)
B4 Olivo-
spinal.
(uncros
sed)
Extra
pyramidal
tract
C1 to C5 Inferior
olivary
nucleus
Anterior grey
column cells

Segment
Beginning 1st
termination
B5 Vestibulo
spinal.
(uncrosse
d)
Efferent
pathway
for equi-
libratory
control
C1 to S5 Lateral
vestibular
nucleus
Anterior grey
column cells
B6 Tecto-
spinal.
(crossed)
Efferent
pathway
for visual
reflexes
C1 to C5 superior
colliculus
Anterior grey
column cells

ASCENDING TRACTS
Segment
Beginning 1st
termination
1 Lateral
spino
thalamic
(crossed
Pain &
temp.
from
opp.half
of body
C1 to S5 Substantia
gelatinosa
of post.
Grey
column
Postero-
lateral
ventral
nucleus of
thalamus
2 Anterior
spino
thalamic
(crossed
Touch &
pressure
from
opposite
half of
body
C1 to S5 Posterior
grey
column of
opposite
side
Postero-
lateral
ventral
nucleus of
thalamus

Segment
Beginning 1st
termination
3 Fasciculus
gracilis.
(uncrosse
d)
Conscious
proprio-
ception,
discrimi-
natory
touch
S5 to T7 Dorsal
root
ganglion
cells
Nucleus
gracilis
4 Fasciculus
cuneatus.
(uncrosse
d)
Vibratory
sense
stereo-
gnosis
T1 to T5 Dorsal
root
ganglion
cells
Nucleus
cuneatus

Segment
Beginning 1st
termination
5 Posterior
(dorsal)
spino
cerebe-
llar.
(uncross
ed)
Unconscious
proprio-
ception to
cerebellum
C1 to L2 Thoracic
nucleus of
posterior
grey
column
Vermis of
cerebellum
(via inf.
Cerebellar
peduncle).
6 Anterior
(ventral)
spino
cerebe-
llar.
(crossed)
Cerebellum
adjustments
of muscle
tone
C1 to L2 Posterior
grey
column
same side
Vermis of
cerebellum
(via sup.
Cerebellar
peduncle).

Segment
Beginning 1st
termination
7 Spino-
olivary.
(uncros
sed)
Proprio-
ceptive
sense.
C1 to S5 Posterior
grey
column.
Dorsal and
medial
accessory
olivary nuclei.
8 Spino-
tectal.
(crosse
d)
Afferent
limb of
reflex
movements
of eyes &
head
towards
source of
stimulation
C1 to C6 Posterior
grey
column of
opposite
side.
Tectum or
superior
colliculus of
midbrain.

 The vertebral arteries are the main source of blood
to the spinal cord.
 One anterior and two posterior spinal arteries are
supplying blood to the spinal cord (branches from
the vertebral arteries).

Clinical Anatomy :
 Poliomyelitis : is a viral disease which involves
anterior horn cell leading to paralysis of affected
segment.
 Syringomyelia : condition in which there is dilatation
of central canal of spinal cord beginning in cervical
region.

Pyramidal Tract.
Pain & Temperature Pathway.
Pathway of Touch.
Optic (Visual) Pathway.
Auditory (hearing) Pathway.
Taste Pathway.

PYRAMIDAL TRACT
 This is a descending tract, extending
from cerebral cortex to various
motor nuclei of cranial & spinal
nerves.
 Each pyramidal tract contains about
1 million fibres.
 Origin : motor area (no.4) of cortex,
premotor area (no.6), & sensory
area (no.3,2,1).
 Terminates : before termination, it
cross to opposite side. They
terminate through an interneuron,
in the motor nuclei of cranial nerves
& to the ant. horn cells of the spinal
cord.

Clinical Anatomy
If fibres of the pyramidal tracts are damaged, this will
give rise to an upper motor neuron syndrome.
If the cortico bulbar tract is damaged on only one side,
then only the lower face will be affected, however if
there is involvement of both the left and right tracts,
then the result is pseudo bulbar palsy. This causes
problems with swallowing, speaking, and emotional
lability.

PAIN & TEMPERATURE PATHWAY
 Receptors :
 free nerve endings for pain.
 End bulbs Krause for cold.
 Organs of Ruffini for warmth, &
Golgi – Mazzoni for heat.
 1st Neuron – locates in the dorsal
root ganglia. Peripheral process of
neurons in the ganglia constitute
the sensory nerves. The central
processes of neuron passes
through the dorsal nerve root to
enter the spinal cord, where they
synapse with 2nd neuron.

 2nd Neuron : located in the grey
matter of spinal cord. Their axon
from lateral spinothalamic tract.
The tract is crossed. It ascends
through the lateral white column
of the spinal cord to enter the
brain stem. In the brain stem, this
tract is referred to as the spinal
lemniscus to end in the thalamus.
 3rd Neuron : lies in the postero-
lateral ventral nucleus of the
thalamus. Fibres arising in this
nucleus pass through the internal
capsule and the corona radiata to
reach the somatosensory area
(Area 3,1,2).

PATHWAY OF TOUCH
The 1st Neuron is for pain &
temperature pathway. The 2nd
neuron are different for fine
touch & for crude touch.
PATHWAY OF FINE TOUCH :
 The central processes of the
neurons in the dorsal nerve
root ganglia enter the
posterior white column of the
spinal cord & form the
fasciculus gracilis & the
fasciculus cuneatus.

 2nd neuron lies in the nucleus
gracilis or nucleus cuneatus. It
gives off the internal arcuate fibres
which cross to the opposite side
through the sensory decussation.
Reaching the other side they runs
upwards as the medial lemniscus.
The medial lemniscus ends in the
postero lateral ventral nucleus of
the thalamus.
 Fibres starting in the thalamus
pass through the internal capsule
& the corona radiata & end in the
somato sensory area of the
cerebral cortex.

 PATHWAY FOR CRUDE TOUCH :
 The central process of neuron in
dorsal root ganglia terminate in
the grey matter of the spinal
cord.
 2nd neuron lies in the spinal cord.
Axon of those neurons cross the
midline & form anterior spino-
thalamic tract. In the brainstem,
this tract merge with the medial
lemniscus.
 3rd neuron terminate in the
somatosensory area of cerebral
cortex (Area 3, 1, 2).

OPTIC (VISUAL) PATHWAY
 Structures in visual pathway :
 Retina.
 Optic nerve.
 Optic chiasma.
 Optic tract, with its lateral &
medial roots.
 Lateral geniculate body.
 Optic radiation.
 Visual area in the cortex.

 The visual system is the
part of the central nervous
system.
 The visual system includes
the eyes, the connecting
pathways through to the
visual cortex and other
parts of the brain.

 Information from the right
visual field (now on the left
side of the brain) travels in
the left optic tract.
 Information from the left
visual field travels in the
right optic tract.
 Each optic tract terminates
in the lateral geniculate
nucleus (LGN) in the
thalamus.

 Optic radiation begins from
the lateral geniculate body,
passes through the
retrolentiform part of the
internal capsule, and ends in
the visual cortex.
 The optic radiations in the
visual area (Area 17) where
the colour, size, shape,
motion, illumination, and
transparency are
appreciated separately.

EFFECT ON LESIONS OF DIFFERENT
PART OF VISUAL PATHWAYS
 Ipsilateral blindness : lesion of
the optic nerve.
 Bitemporal hemi anopia : mid-
sagittal of the optic chiasma.
 Contralateral homonymous
hemi anopia : lesion of the optic
tract and optic radiation.
 Contralateral homonymous
hemi anopia with macular
sparing : lesion of the visual
cortex.

PATHAWAY OF HEARING
 The auditory system is the
sensory system for the sense
of hearing (Area 41,42).
 Pathway :
 1st Neurons – located in
spiral ganglion.
 Peripheral processes
innervate the organ of corti,
while the central processes
terminate in the dorsal &
ventral cochlear nuclei.

 2nd Neurons – lie in the dorsal
& ventral cochlear nuclei.
 Most of the axons arising in
these nuclei cross to the
opposite side.
 Termination : in the superior
Olivary nucleus.

 3rd Neurons : lies superior
olivary nucleus.
 Axons from lemniscus &
reach the inferior Colliculus.
 4th Neurons : lies in the
inferior Colliculus.
 Axons passes through the
inferior brachium to reach
the medial geniculate body.

 5th Neurons : lie in the
medial geniculate body.
 Axons passes through the
sublentiform part of the
internal capsule to reach
auditory area (Area 41,42)
in the temporal lobe.

REFERENCES :
 BD Chaurasia’s Human Anatomy – Head, Neck and Brain.
4th Edition.
 Grey’s Anatomy for students.
 Clinically Oriented Anatomy- Keith L.Moore.8th Edition

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