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1. KAMPALA INTERNATIONAL
UNIVERSITY-WC
DEPARTMENT OF SURGERY
PRESENTER:-ABDIFATAH ABDI ALI
COURSE UNIT:- ADVANCED ANATOMY II
INTERNAL FEATURES OF CEREBRAL
HEMISPHERES
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2. OUTLINE
INTERNAL FEATURES OF CEREBRAL HEMISPHERES
Association Fibres
Commissural Fibres
Projection Fibres
 Internal Capsule
Ascending Fibres
Descending Fibres
Clinical correlation
References
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3. INTRODUCTIONS OF CEREBRUM
 The cerebrum is the largest part
of the brain.
 The brain consists of two
cerebral hemisphere connected
by a mass of white matter
called the corpus callosum.
 The cavity inside each
hemisphere is called the lateral
ventricle.
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4. White Matter of Cerebral Hemispheres
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5. TYPES OF NERONS FIBRES IN WHITE
MATTER
1. Association fibres.
2. Commissural fibres.
3. Projection fibres.
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7. Association Fibres
 The association fibres
interconnect the different
cerebral cortex in the same
hemisphere(within it self)
1. Short association fibres,
which interconnect the
adjacent gyri
2. Long association fibres,
interconnect the widely
separated gyri
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9. Commissural Fibres
The commissural fibres
interconnect the identical
cortical areas of the two
cerebral hemispheres The
important commissures of
the brain are as follows:
1. Corpus callosum.
2. Anterior commissure.
3. Posterior commissure.
4. Hippocampal commissure.
5. Habenular commissure
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11. CORPUS CALLOSUM
 CORPUS CALLOSUM :-The
corpus callosum is the largest
commissure of the brain.
 External features of corpus
callosum: Corpus callosum forms a
median longitudinal cerebral
fissure connecting the medial
surfaces of the two cerebral
hemispheres.
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13. Projection Fibres
The projection fibres connect
the cerebral cortex to the
subcortical centres and spinal
cord
 1. Corticofugal fibres,
which go away from the
cortex (cortical efferents) to
centres in the other parts of
the CNS.
2. Corticopetal fibres, which
come to the cerebral cortex
from the other centres in the
CNS.
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14. Internal Capsule
The internal capsule is a compact bundle of
projection fibres between the thalamus and
caudate nucleus medially and the lentiform
nucleus laterally.
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15. Descending nerve fibres which connect the
cerebral cortex to the brainstem and spinal cord.
The afferent (sensory) fibres pass up from
thalamus to the cerebral cortex
 Efferent (motor) fibres pass down from the
cerebral cortex to the cerebral peduncle of the
midbrain.
sensory and motor fibres of internal capsule are
mainly responsible for the sensory and motor
innervation of the opposite half of the body
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16. Constituent motor and sensory fibres in
different parts of the internal capsule
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17. TRACTS
(a) Ascending (sensory or afferent).
(b) Descending (motor or efferent).
They serve to join the brain to the spinal cord
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18. ASCENDING TRACTS
ASCEN DING TRACTS On entering the spinal
cord, the sensory nerve fibers of different sizes and
functions are sorted out and segregated into nerve
bundles
The ascending tracts conduct Are two types
1. Exteroceptive information originates from outside
the body, such as pain, temperature, and touch.
2. Proprioceptive information originates from inside
the body, for example, from muscles and joints.
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19. SENSORY {ASCENDING)SPINAL
TRACTS}
 The ascending sensory pathway from
the sensory nerve ending to the
cerebral cortex. Note the three neurons
involved.
 Carry impulses from pain, thermal,
tactile, muscle and joint receptors to
the brain. Some of this information
eventually reaches a conscious level
(the cerebral cortex), while some is
destined for subconscious centers (e.g.
the cerebellum).
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20.  Three major pathways carry sensory information:
 Posterior column (Gracile & Cuneate fasciculi)
 Anterolateral pathway (Spinothalamic)
Spinocerebellar pathway
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21. Dorsal Column
Posterior Column:
 Contains two tracts;
Fasciculus Gracilis (FG) &
Fasciculus Cuneatus (FC)
 Carry impulses concerned with
proprioception and
discriminative touch
from ipsilateral side of the body
Contain the axons of primary afferent
neurons that have entered cord
through dorsal roots of spinal nerves
 FG contains fibers received at sacral,
lumbar and lower thoracic levels,
 FC contains fibers received at upper
thoracic and cervical levels
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22.  Fibers ascend without interruption
where they terminate upon 2nd
order neurons in nucleus gracilis
and nucleus cuneatus
 The axons of the 2nd order
neurons decussate in the medulla
as internal arcuate fibers and
ascend through the brain stem as
medial lemniscus.
 The medial lemniscus terminates
in the ventral posterior nucleus
of the thalamus (3rd order
neurons), which project to the
somatosensory cortex
(thalamocortical fibers)
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23. Spinothalamic Tracts
 Located lateral and
ventral to the ventral
horn.
 Carry impulses
concerned with; pain
and thermal
sensations (Lateral
tract) and non-
discriminative
touch and pressure
(Anterior tract).
 In brain stem,
constitute the spinal
lemniscus.
 Information is sent to
the primary sensory
cortex on the
opposite side of the
body
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24. Lateral Spinothalamic
Tract
 Function:
 Carries pain & Temperature to
thalamus and sensory area of the
cerebral cortex.
 Neurones: 3 Neurones
 Neurone I: Small cells in the dorsal
root ganglia.
 Neurone II: Cells of substantia
gelatinosa of Rolandi in the
posterior horn.
 Neurone III: Cells of (VP) nucleus of
the thalamus.
 The spinothalamic tract contains
second-order neurones, the cell
bodies of which lie in the
contralateral dorsal horn.
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25. Anterior Spinothalamic
Tract
 Function:
• Carries crude touch & pressure to
thalamus and sensory cortex.
 Neurones: 3 Neurones
• Neurone I:
Medium sized cells in the dorsal
root ganglia.
• Neurone II:
Cells of main sensory nucleus or
(nucleus proprius).
• Neurone III:
Cells of VP nucleus of thalamus.
 Effect of lesion:
Loss of crude touch sensation below
the level of the lesion.
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26. Spinocerebellar
Tracts
• The spinocerebellar system
consists of a sequence of only two
neurons;
• Neurone I:Large cells of dorsal root
ganglia.
• Neurone II: cells of the nucleus
dorsalis (Clark's nucleus.
• Two tracts: Dorsal &Ventral
• Located near the dorsolateral and
ventrolateral surfaces of the cord
• Contain axons of the second order
neurons
• Carry information derived from
muscle spindles, Golgi tendon
organs and tectile receptors to the
cerebellum
• for the control of posture and
coordination of movements
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27. Posterior Spinocerebellar Tract
• Present only above level L3
• The cell bodies of 2nd order
neuron lie in Clark’s column
• Axons of 2nd order neuron
terminate ipsilaterally
(uncrossed) in the cerebellar
cortex by entering through the
inferior cerebellar peduncle.
• Posterior spinocerebellar
tract convey sensory
information to the same side
of the cerebellum
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28. Ventral (Anterior)Spinocerebellar Tract
 The cell bodies of 2nd order
neuron lie in base of the dorsal
horn of the lumbosacral
segments
 Axons of 2nd order neuron
cross to opposite side, ascend
as far as the midbrain, and
then make a sharp turn
caudally and enter the
superior cerebellar peduncle
 The fibers cross the midline for
a second time within the
cerebellum before terminating
in the cerebellar cortex
 Ventral spinocerebellar tract
convey sensory information to
the same side of the
cerebellum
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29. Functions
 Corticospinal tracts are the pathways concerned with voluntary,
discrete, skilled movements, especially distal parts of the limbs.
 Reticulospinal tracts may facilitate or inhibit the activity of the
motor neurons in the anterior gray columns
• Tectospinal tract is concerned with reflex postural movements in
response to visual stimuli.
• Rubrospinal tract acts facilitates the activity of flexor muscles and
inhibits the activity of extensor or antigravity muscles.
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30. Clinical correlation
Lesions of internal capsule: The internal capsule is
frequently involved in the cerebrovascular disorders.
The most common cause of arterial hemorrhage is suffering
from high blood pressure. The hemorrhage commonly
occurs due to rupture of the Charcot’s artery, branch of the
middle cerebral artery (also called Charcot’s artery of
cerebral hemorrhage), which supplies the posterior limb of
the internal capsule.
Damage to the internal capsule caused by hemorrhage or
infarction, leads to loss of sensations and spastic paralysis of
the opposite half of the body (contralateral hemiplegia).
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31. Ascending Tract Injury
Anterior spinothalamic truct Destruction of this tract
produces contralateral loss of pain and thermal
sensibilities below the level of the lesion.
Lateral spinothalamic Destruction of this tract produces
contralateral loss of light touch and pressure sensibilities
below the level of the lesion.
Syringomyelia, (widening of the central canal) leads to
Loss of pain & temperature below the level of the
lesion because the spinothalamic axons decussate to the
opposite side of the cord by passing through the ventral
white commissure, which lies ventral to the central canal
of the cord,.
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32. Upper Motor Neuron
Lesions
The following clinical signs are present in lesions restricted
to the other descending tracts:
1. Severe paralysis with little or no muscle atrophy (except
secondary to disuse).
2. Spasticity or hypertonicity of the muscles. The lower
limb is maintained in extension, and the upper limb is
maintained in flexion.
3. Exaggerated deep muscle reflexes and clonus may be
present in the flexors of the fingers, the quadriceps femoris,
and the calf muscles.
4. Clasp-knife reaction. When passive movement of a joint
is attempted, muscle spasticity produces resistance.
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1. Muscles exhibit flaccid paralysis.
2. Muscles atrophy.
3. Muscles lose reflexes.
4. Muscular fasciculation (muscle
twitching)
5. Muscular contracture (shortening of
the paralyzed muscles
Lower Motor Neuron
Lesions

33. TYPES OF PARALYSIS
1. Hemiplegia is a paralysis of one side of the
body and includes the upper limb, one side of
the trunk, and the lower limb.
2. Monoplegia is paralysis of one limb only.
3. Diplegia is paralysis of two corresponding
limbs (i.e., arms or legs).
4. Paraplegia is paralysis of the two lower limbs.
5. Quadriplegia is paralysis of all four limbs.
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34. REFERANCE
1. Snell’s Clinical Neuroanatomy
(Ryan Splittgerber) (z-lib.org) (
2. Textbook of Anatomy Head, Neck,
and Brain. (Vishram Singh) (z-
lib.org)
3. Google support picture
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