Pair_of _Cranial_nerve_ (from_ CN1_ TO_ CN4)

there are 12 pair of cranial nerve that supply the structure of the head,neck,thorax and abdomen.
now we are going to start from cranial nerve 1 to 4

1. Dr. NDAYISABA CORNEILLE
CEO of CHG
MBChB,DCM,BCSIT,CCNA
Supported BY 1

2. Cranial nerves:
they belong to the peripheral nervous system
12 pairs:

olfactory nerve (I)
optic nerve (II)
oculomotory nerve (III)
trochlear nerve (IV)
trigeminal nerve (V)
abducens nerve (VI)
facial nerve (VII)
vestibulocochlear (stato-acustic) nerve (VIII)
glossopharyngeal nerve (IX)
vagus nerve (X)
accessory nerve (XI)
hypoglossal nerve (XII)



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3. Cranial nerves
Olfactory nerve (I)
Optic chiasma (II)
Optic tract (II)
Oculomotory nerve (III)
Trochlear nerve (IV)
Trigeminal nerve (V)
Facial nerve (VII)
Vestibulocochlear nerve (VIII)
Glossopharyngeal+vagus nerves
(IX,X)
Accessory nerve (XI)
Hypoglossal nerve (XII) Abducens nerve (VI) 7/23/2023 Dr Ndayisaba Corneille 3

4. Cranial nerves
Functionally:
Somatic: voluntary
Visceral (vegetative):
autonom, unvoluntary
Sensory:
about the outside
world; structures
developed from
embryonic ectoderm
and somatic mesoderm
Motory:
controlling voluntary
muscles, derived from
somites and embryonic
gill arches
Sensory:
viscera
developed
from ectoderm
and splanchnic
mesoderm
Motory:
controlling
function of the
viscera
(symphatetic and
parasymphatetic)
general somatic afferent
GSA
somatic efferent
SE
general visceral afferent
GVS
visceral efferent
VE
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5. •Olfactory nerve (I): is developing as an early part of the primitive
telencephalon

•Optic nerve (II): is developing as an outpouching from the
diencephalon

•Carnial nerves III to XII:
originate from the brain stem

are embryologically homologous with spinal nerves

nuclei of them derived originally from cell columns
homologous with the columns of the spinal cord
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6. Special sensory cranial nerves
•Olfactory nerve (I)

•Optic nerve (II)

•Vestibulocochlear nerve (VIII)
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7. Nuclei of the cranial nerves
Cranial nerve Site of nucleus
1st, 2nd directly go to the
cerebral cortex
3rd, 4th midbrain
5th, 6th, 7th, 8th pons
9th,10th,11th,12th medulla oblongata
More attention:
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8. Olfactory nerve(I)
•Olfactory epithelia lines the roof of the
nose. It contains bipolar neurons whose
peripheral processes are the olfactory
receptors.
•Olfactory nerve is the central processeses
of these bipolar neurons (about 20 )as
they traverse the cribriform plate of the
ethmoid bone to end in the olfactory bulb.
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10. Olfactory nerve.

Olfactory bulb lies on the orbital suface of
the frontal lobe and continues as the
olfactory tract.
The olfactory tract extends into the anterior
perforated substance lateral to the optioc
chiasma to form 3 olfactory stria.
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11. Olfactory nerve
•1. lateral olfactory stria ends in primary
olfactory cortex
•2.intermediate olfactory stria ends in
olfactory tubercle in anterior perforated
substance
•3.medial olfactory stria ends in
paraterminal gyrus &para olfactory gyrus
(parts of the septal area and anterior
commissure)
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12. •Primary olfactory cortex lies in 3 regions
i.e uncus, part of amygdala and apex of
insula.
•Secondary olfactory cortex is entorhinal
area 28 in the anterior part of the
parahipocampal gyrus.
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13. Applied anatomy C.C
•Olfactory pathway is linked to the limbic
system,it’s the only sesation that reaches
the cortex without relaying to the
thalamus.
•Anosmia is loss of smell. Unilateral due to
frontal lobe tumour or bilateral due to
fracture of the cribriform plate.
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14. Optic nerve.(II)
VISUAL PATHWAY .
•Formed of 3 successive neurons.(two in
the retina while 3
rd
in the lateral geniculate
body.
•1
st
order neurone from bipolar cells of the
retina , 2
nd
order neurone from ganglion
cells of the retina.
•Their axons form the optic nerve and the
two optic nerves meet at the optic
chiasma.

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15. Optic Nerve
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16. Optic Nerve
•Axons of retinal
ganglion cells
converge at the optic
disc and pass into
optic nerve
•Then the nerve passes
posteromedially in the
orbit, exits through
the optic canal to
enter the middle
cranial fossa to joins
the optic chiasma.
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17. Visual Pathway
Photoreceptors:
Rods & Cones of retina
3 neuron pathway
1
st
order neurons:
Bipolar cells of retina
2
nd
order neurons:
Ganglion cells of
retina. Their axons form
the optic nerve
3
rd
order neurons:
Neurons in the lateral
geniculate body. Their
axons terminate in
primary visual cortex.

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18. VISUAL PATHWAY
•In the optic chiasma fibres from each nasal
half of the retina decussate(cross) to the
contralateral optic tract where as fibres
from the temporal half of the retina pass
uncrossed to the ipsilateral optic tract.
•Macular fibres partially decussate in the
chiasma and pass to optic tracts of both
sides.
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19. VISUAL PATHWAY
•The optic tract contains fibres from the
temporal side of the same side and nasal
fibres ffrom the opposite side and mucular
fibres from both sides.
•The optic tract divides into medial and
lateral roots.
•(medial roots to Medial geniculate
body,MGB), (lateral roots to lateral
geniculate body,LGB and superior
colliculus of midbrain and pretectal area
used in light reflexes) 7/23/2023 Dr Ndayisaba Corneille 19

20. VISUAL PATHWAY
•3
rd
order neuron is formed from the LGB,
the axons move as the optic radiation to
the primary visual cortex area 17 in
occipital lobe supplied by PCA
•Optic radiation passes through the retro
lentiform part of internal capsule splits
into dorsal group from the upper
quadrant of the retina and ventral group
from lower quadrant of retina(Meyers
loop).
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21. Visual Pathway
1.Optic nerve
2.Optic chiasm
3.Optic tract
4.Lateral geniculate
body (nucleus)
5.Optic radiation
6.Visual cortex
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22. Optic Chiasma
•Fibers from the nasal (medial)
half of retina decussate in the
chiasm and join uncrossed
fibers from the temporal
(lateral) half of the retina to
form the optic tract.
•The decussation of nerve fibers
in the chiasm results in the
right optic tract conveying
impulses from the left visual
field and vice versa.
•The partial crossing of optic
nerve fibers in the optic
chiasma is a requirement for
binocular vision.



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23. Optic Tracts
•Fibers in the optic
tracts:
Mainly terminate
in the lateral
geniculate bodies
of the thalamus
A few fibers
terminate in
pretectal area
and superior
colliculus. These
fibers are related
to light reflexes

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24. Optic Radiation
•Optic radiation or
thalam-ocortical or
geniculocalcarine fibers
originating in the lateral
geniculate nucleus.
•Passes through the
retrolenticular part of
the internal capsule to
the visual cortex above
and below the calcarine
sulcus.
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25. Visual Cortex
•The primary visual cortex
(area 17 of Brodmann's)
occupies the upper and lower
lips of the calcarine sulcus on
the medial surface of the
cerebral hemisphere.
The visual association cortex is
extensive, including the whole of
the occipital lobe, the adjacent
posterior part of the parietal lobe.
This cortex is involved in
recognition of objects and
perception of color, depth,
motion, and other aspects of
vision.
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26. Applied anatomy C.C
•Lesions of the visual pathway
Optic nerve-Optic neuritis
Optic chisma-lateral side =ipsilateral nasal
hemi anopia, central part=bitemporal
hemianopia.


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27. Visual Field Deficits
Cut at level :1. A lesion of the right
optic nerve causes a total loss of
vision (blindness) in the right eye
Cut at level :2. A lesion of the optic
chiasm causes a loss of vision in the
temporal half of both visual fields:
bitemporal hemianopsia.
Cut at level: 3 & 4. A lesion of the
right optic tract & right optic
radiation just after the LGN causes
a loss of vision in the left
hemifield: contralateral
homonymous hemianopsia.
A lesion of both visual cortices
causes a complete blindness.
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29. VISUAL REFLEXES
•1. LIGHT(pupillary) REFLEX, shinning light
inone eye leads to constriction of both
pupiils
Direct -same pupil
Indirect /consensual-contralateral pupil
Light reflex pathway.
Optic nerve-optic tract-optic –pretectal
nucleus of both sides-edingerwestphal
nucleus of CNIII-oculomotor nerve-ciliary
ganglion-postganglionic ciliary nerves to
sphinter pupillae muscle=pupillary
constriction .
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30. Applied anatomy C.C
•Funduscopy( optic disc examination)

•Accomodation reflex
•Corneal reflex.

•Read about the pathways.
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31. Examination and clinical finding
•Fundus
•The normal optic disc is
yellowish, oval, clearly
definite margins.

•Fundus
•Optic atrophy: optic
disc becomes pale.

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32. Examination and clinical finding
•Fundus
•Papilledema: main changes:
•Margins of optic disc are blurred.
•Optic disc is pink and hyperemia.
•Physiological cup is obliterated.
•Veins are congested.
•Hemorrhages may be present.
•Causes:
•Raised ICP(intracranial pressure)
•Malignant HT（Hypertension）
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33. Oculomotory nerve (III)
•Somatomotory innervation of the muscles of the eye and
parasympathetic motor innervation to the pupil
cerebral aqueduct
central gray matter

parasympathetic nucleus
(Edinger-Westfal)
somatomotor nucleus
crus cerebri
(cerebral peduncle)
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34. Oculomotory nerve (III)
crus cerebri
(cerebral peduncle)
mamillary body
interpeduncular
fossa
oculomotory
nerve (III)
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35. Cranial nerves innervating the eye’s
muscles: III, IV, VI
sup. oblique m.
lat. rectus m.
trochlear n.
abducens n.
oculomotory n.
ggl. ciliare
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36. •EXTRA-OCULAR
MUSCES (7 muscles).
•1-Levator palpebrae
superioris
• 4 Recti muscles:
•Medial rectus,
•Lateral rectus,
•Superior rectus,
•Inferior rectus
•2 Oblique muscles:
•Superior oblique,
•Inferior oblique.
•NB. All muscles of the
eye are supplied by
the oculomotor nerve
, EXCEPT LR6 + SO4

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37. Occulomotor nerve
Motor for most of extraocular muscles.
Also carries preganglionic
parasympathetic fibers for pupillary
constrictor and ciliary muscle.
Has two nuclei:
1- Main occulomotor nucleus;
Lies in the mid brain, at the level of
superior colliculus
2- Accessory nucleus (Edinger-Westphal
nucleus);
Lies dorsal to the main motor nucleus,
Its cells are preganglionic
parasympathetic neurons.
It receives; Corticonuclear fibers for the
accommodation reflex, and from the
pretectal nucleus for the direct and
consensual pupillary reflexes.

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38. Axons from the oculomotor
nucleus curve ventrally
through the tegmentum and
the red nucleus.
The nerve emerges on the
anterior surface of the
midbrain in the
interpeduncular fossa.
Then it passes forward
between posterior cerebral
and superior cerebellar
arteries.
In the middle cranial fossa it
runs in the lateral wall of
the cavernous sinus, then it
divides into superior and
inferior divisions which
enter the orbit through the
superior orbital fissure.
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39. III, IV, VI cranial nerves
oculomotory n.
trochlear n.
abducens n.
cavernous sinus
sup. orbital fissure
orbit
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40. Axons from the
Edinger-Westphal
nucleus accompany
the oculomotor
nerve fibers to the
orbit, where they
terminate in the
ciliary ganglion.
Postganglionic fibers
pass through the
short ciliary nerves
to the eyeball, where
they supply:
Constrictor
pupillae muscle of
the iris and ciliary
muscle.

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41. Occulomotor nerve supplies:
Motor to:
1.Levator palpebrae superioris
2.Superior rectus muscle
3.Medial rectus muscle
4.Inferior rectus muscle &
5.Inferior oblique muscle.
Parasympathetic fibers to
1- Constrictor pupillae and
2- Ciliary muscles.

It is responsible for;
Elevation of upper eyelid.
Turning the eye upward,
downwards and medially,
Constricting the pupil.
Accommodating reflex of the
eyes.
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42. Occulomotor nerve lesion
•Lesion results in:
–Lateral squint.
–Ptosis.
–Diplopia.
–Pupillary dilatation.
–Loss of accommodation.
–Impaired downward & inward
movement of the eye ball on the
damaged side.
The preganglionic parasympathetic fibers
run superficially in the nerve and are
therefore the first axons to suffer when a
nerve is affected by external pressure.
Consequently, the first sign of
compression of the occulomotor nerve is
ipsilateral slowness of the pupillary
response to light. 7/23/2023 Dr Ndayisaba Corneille 42

43. Trochlear Nerve
Type: motor
Small motor nucleus
located in the
periaqueductal grey
matter at the level of
inferior colliculus.
Fibers curve
backwards and
decussate.
The nerve emerges
immediately caudal
to the inferior
colliculus, on the
dorsal surface of
brain stem.

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44. Trochlear nerve (IV)

Somatomotory innervation of the eye muscle: sup. oglique
inf. colliculus
motor nucleus of
cranial n. IV.
red nuclues
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45. Trochlear nerve (IV)
thalamus
pineal body
midbrain trochlear nerve
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46. Trochlear nerve (IV)
pons
trochlear nerve
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47. It passes forward
through middle
cranial fossa in the
lateral wall of the
cavernous sinus.
The nerve then enters
the orbit through the
superior orbital
fissure.
It supplies;
 Superior oblique muscle,
(only one muscle).
Its function;
 Rotates the eye ball
downwards and laterally.
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48. Trochlear Nerve
lesion

Lesion results in
diplopia &
Inability to rotate the
eye infero-laterally.
So, the eye deviates;
upward and slightly
inward.
This person has
difficulty in walking
downstairs

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49. END
7/23/2023
THANKS FOR LISTENING
By
DR NDAYISABA CORNEILLE
MBChB,DCM,BCSIT,CCNA

Contact us: [email protected]/
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Dr Ndayisaba Corneille 49