cranial nerves.ppt anatomy and physiology

cranial nerves.ppt

1. Cranial Nerves

4. Cranial Nerves
I:Olfactory
II:Optic
III:Oculomotor
IV:Trochlear
V:Trigeminal
VI:Abducens
VII: Facial
VIII:Vestibulocochlear
IX:Glossopharyngeal
X:Vagus
XI:Accessory
XII: Hypoglossal

5. Cranial nerves
The base of the brain
showing locations of
cranial nerves
There are 12, pairedcranial
nerves.
The first 2 cranial Ns.attach
directly to forebrain (frontal lobe) ,
while the rest attach to brain
stem.
Olfactory systemis attached
to forebrain and is referred to as
the limbic system,

7. Classification of cranial nerves
Sensory cranial nerves: contain only afferent (sensory) fibers
–ⅠOlfactory nerve
–ⅡOptic nerve
–Ⅷ Vestibulocochlear nerve
Motor cranial nerves: contain only efferent (motor) fibers
–Ⅲ Oculomotor nerve
–Ⅳ Trochlear nerve
–ⅥAbducent nerve
–Ⅺ Accessory nerv
–Ⅻ Hypoglossal nerve
Mixed nerves: contain both sensory and motor fibers---
–ⅤTrigeminal nerve,
–Ⅶ Facial nerve,
–ⅨGlossopharyngeal nerve
–ⅩVagus nerve

8. Mnemonic
On
Old
Olympus’
Tower
Top
A
Fin
And
German
Viewed
A
Hop

9. MNEMONIC
OLFACTORY
OPTIC
OCULOMOTOR
TROCHLEAR
TRIGEMINAL
ABDUCENS
FACIAL
VESTIBULOCOCHLEAR
GLOSSOPHARYNGEAL
VAGUS
ACCESSORY
HYPOGLOSSAL
OH
ONCE
ONE
TAKES
THE
ANATOMY
FINAL
VERY
GOOD
VACATION
A-HEAD

11. CN I: OLFACTORY
Cranial nerve I
Function:
–smell
Clinical test for
damage:
–determine whether
a person can smell
something aromatic

12. CN II: OPTIC
Cranial nerve II
Function:
–vision
Clinical test for
damage:
–tests peripheral vision
and visual acuity
Effects of damage:
–blindness in part or all
of the visual field

13. CNIII: OCULOMOTOR
Cranial nerve III
Function:
–eye movements, opening of
eyelid, constriction of pupil,
focusing, proprioception
Clinical tests for injury:
–differences in pupil size;
pupillary response to light; eye
tracking
Effects of damage
–dropping eyelid, dilated pupil,
double vision

14. CNIV: TROCHLEAR
Cranial nerve IV
Function: eye movements
and proprioception
Clinical test for injury: ability
to rotate eye inferolaterally
Effects of damage –double
vision, patient tilts head
toward affected side

15. CN V: TRIGEMINAL
Cranial nerve V
Function: sensory nerve of the
face
Clinical test for injury:
–corneal reflex; sense of
touch, pain, and
temperature; clench teeth;
move mandible side to side
Effects of damage:
–loss of sensation and
impaired chewing

16. CN VI: ABDUCENS AND
CN VII: FACIAL
Cranial Nerve VI
Function: Eye
movements
Clinical test: lateral eye
movement
Effects of damage:
inability to rotate eye
laterally; at rest –eye
rotates medially
because of action of
antagonistic muscles
Cranial Nerve VII
Function: facial
expression; sense of
taste
Clinical test: motor
functions –close eyes,
smile, whistle, frown,
raise eyebrows; taste
Effects of damage:
inability to control
facial muscles;
distorted sense of taste

17. CN VIII:
VESTIBULOCOCHLEAR
Cranial Nerve VIII
Function: hearing and equilibrium
Clinical tests: test hearing, balance,
and ability to walk a straight line
Effects of damage: deafness,
dizziness, nausea, loss of balance, and
nystagmus

18. CN IX: GLOSSOPHARANGEAL
AND CN X: VAGUS
Cranial Nerve IX
Function: swallowing,
salivation, gagging; touch,
pressure, taste, and pain
sensations from tongue,
pharynx, and outer ear
Clinical tests: gag reflex,
swallowing, and coughing
Effects of damage:
difficulty swallowing
Cranial Nerve X
Function: swallowing; taste;
speech; respiratory, CV, and
GI regulation; sensations of
hunger, fullness, and
intestinal discomfort
Clinical tests: test with
cranial nerve IX
Effects of damage:
hoarseness or loss of voice;
impaired swallowing and GI
motility

19. CN XI: ACCESSORY AND
CN XII: HYPOGLOSSAL
Cranial Nerve XI
Function: swallowing; head,
neck, and shoulder
movements
Clinical tests: rotate head
and shrug shoulders against
resistance
Effects of damage: impaired
movement of head, neck,
and shoulders; paralysis of
sternocleidomastoid
Cranial Nerve XII
Function: tongue movements
of speech, food
manipulation, and
swallowing
Clinical test: tongue function
Effects of damage: difficulty
in speech and swallowing;
atrophy of tongue; inability
to stick out (protrude)
tongue

20. Olfactory nerve
Olfactory mucosa (SVA)→ Cribriform foramina → Olfactory
bulb

21. Optic nerve
Ganglion cell (SSA)→ Optic canal → Lateral geniculate body

22. Oculomotor nucleus :lies at
the base of periaqueductal grey of
midbrain at the level of superior
colliculus.Its efferents run in
oculomotor N. to innervate levator
palpebrae superioris + all
extraocular Ms. Except L.R & S.O
Trochlear nucleus :lies at the
ventral part of periaqueductal grey
of midbrain at the level of inferior
colliculus.Its efferents run in
trochlear N. to innervate
S.O.muscle.

23. Oculomotor& trochlear Nerves
Anterior view of midbrain
Oculomotor nerve :emerges
from the medial aspect of each
cerebral peduncle e.g. through
the interpeduncular fossa.
Posterior view of midbrain

25. IV : Trochlear Nerve :
Carries only somatic motor
efferentsfrom the trochlear
nucleus in midbrain(level of
inferiorcolliculus)to supply
theS.O.of opposite side.
The only nerve emergesfrom
the post.surface of brain -
stem,then appears on the
ventral aspect of the
midbrain.
It runs in lateral wall of
cavernus sinus and enter the
orbit through sup. orbital
fissure to supply S.O.

26. Trigeminal motor nucleus :lies in
the tegmentum of the mid-ponsand
run in mandibular branch of
trigeminal N. to supply structures of
1
st
pharyngeal arch as Muscles. of
mustication, mylohyoid, ant.belly of
digastric, tensor tympani (middle ear)
& tensor veli palatini.(soft palate).

28. V : Trigeminal Nerve :
Superficial distribution of sensory
fibres of the 3 divisions of trigeminal
nerve.
It is the largest cranial N
Distributed via
ophthalmic, maxillaryand
mandibularto Ms.of
mastications (Ms.of 1
st
arch).
It attaches to the
ventrolateralaspect of pons
by 2 roots (a large sensory
laterally & a smaller motor
medially).

31. VI : AbducensNerve :
Like trochlear N., contains
only somatic motor neurones
in the abducens nucleus ,which
located incaudal ponsbeneath
the floor of 4
th
ventricle.
Fibres emergefrom the
ventral surface of brain stem at
the junctionbetween the pons
& pyramid ofM.O
The nerve then passes in the
cavernous sinus and enter orbit
through sup. orbital fissure to
supply L.R muscleto abduct
the eyeball.

33. VII : Facial Nerve :
Motor Fs.of facial nucleus in pons looping over
abducens nucleus , then leaving the brain stem to supply
: Ms. of facial expression ,platysma ,stylohyoid ,
post.belly of digastric & stapedius of middle ear.
Facial motor nucleusreceives other afferents from area
of brain stem for mediation of certain reflexes and also
from cerebral cortex , (cortico-bulbar pyramidal tract).

36. Course: leaves skull
through internal acoustic
meatus, facial canal and
stylomastoid foramen, it
then enters parotid
gland where it divides
into five branches which
supply facial muscles

37. Branches outside of facial canal
Temporal
Zygomatic
Buccal
Marginal mandibular
Cervical

38. Bell’s Palsy :LMN facial paralysis
It is due to acute unilateral inflammationof facial
nerve within the skull (in facial canal).
Manifested by paralysis of facial muscles of upper &
lower parts of face on the same side of lesion
Manifested by pain around ear, -failure to close
eye,absentcorneal reflex,-loss of taste sensation
in anterior 2/3 of tongue, & hyperacusis
=increased sound perception due to paralysis of
stapedius.

39. Bel’s palsy Injury to the facial nerve

40. Vestibulocochlear nerve
Vestibular ganglion(SSA)↘ ↗Vestibular nuclei
Internal acoustic meatus
Cochlear ganglion (SSA)↗ ↘Cochlear nuclei

44. IX : Glossopharyngeal Nerve :
Glossopharyngeal nerve nuclei &
their central connections
It is a mixed N. ,attached
lateral to olive inrostral
medullaand leaves the skull
through jugular foramen.
It receives afferent Fs.
From :1-Receptors of
general sensationin pharynx,
post.1/3 of tongue,
eustachian tube & middle ear.
2-Taste budsof pharynx &
post.1/3 of tongue.
3-Chemoreceptorsin carotid
body & Baroreceptorsin the
carotid sinus.

46. X : VagusNerve :
Vagus nerve Nuclei & their
central connections.
It is mixed nerve,attached
lateral to olive of medulla
caudal to glosso-pharyngeal
N. in groove between olive &
inf.cerebellar peduncle.
It recevies afferent
Fs.from :1-Receptors for
general sensationin pharynx,
larynx, tympanic membrane,
ext.acoustic meatus. 2-
Chemoreceptorsin aortic
bodies and baroreceptorsin
aortic arch.
3-Receptors in thoracic &
abdominal viscera.

47. Course
Exits the skull from jugular foramen
Descends in the neck in carotid sheath between
internal (or common) carotid artery and internal
jugular vein
Right vagusnerve
Enter thoracic inlet on right side of trachea
Travels downward posterior to right
brachiocephalic vein and superior vena cava
Passes posterior to right lung root
Forms posterior esophageal plexus
Forms posterior vagal trunk at esophageal
hiatus where it leaves thorax and passes into
abdominal cavity, then divides into posterior
gastric and celiac branches

48. Left vagusnerve
Enter thoracic inlet between left common
carotid and left subclavianarteries, posterior to
left brachiocephalic vein
Crosses aortic arch where left recurrent
laryngeal nerve branches off
Passes posterior to left lung root
Forms anterior esophageal plexus
Forms anterior vagal trunk at esophageal
hiatus where it leaves thorax and passes into
abdominal cavity , then divides into anterior
gastric and hepatic branches

50. XI :Accessory Nerve :
Diagram of caudal medulla & rostral
spinal cord to illustrate origin and
course of vagus & accessory nerves.
It is purely motor, consists
of cranial part & spinal part.
The cranial partemerges
from lateral aspect of medulla
below vagus N. It arises from
caudal part of nucleus ambiguus
of medulla.
At the level of jugular foramen
it joins vagus N. to supply Ms. of
soft palate, pharynx & larynx.
Spinal root of accessory
arises from upper 5 cervical
spinal cord segments. It
ascends to the side of medulla to
join the cranial root till the
jugular F., it separates to supply
sternomastoid & trapezius Ms.

51. XII : Hypoglossal Nerve :
T.S.of medulla to illustrate
origin & course of
hypoglossal nerve.
It is purely motor, supplying
all extrinsic & intrinsic Ms. of
tongueexceptpalatoglossus (by
pharyngeal plexus).
It arises from hypoglossal
nucleus inmedulla ( beneath
floor of 4
th
V.).
It emerges from M.O. between
olive &pyramid.
It also receives coticobulbar
Fs.from contralateral motor
cortex, which subserve
voluntary movements of tongue
as occur in speech.

53. Hypoglossal nerve
Hypoglossal nerve

54. Course
Arises from anterolateral aspect of medulla as 10-
15 series of rootlets
Rootlets fuse to form two roots
Enters hypoglossal canal
Fuse to form single nerve and leaves cranial cavity
Passing forwards between internal jugular vein and
internal carotid artery
Finally runs superficial to both external and internal
carotid arteries
Reaches above the hyoid bone
Supplies all intrinsic and extrinsic muscles of tongue
except palatoglossus