Download Chap 13. 뇌신경

Chap 13. 뇌신경
Introduction
• Cranial N. : exchange information between
the periphery and the brain
– cranial N. 12 쌍이 뇌의 표면에서 머리와 목의 구조로
innervation
– cranial nerve X(vagus N)는 머리와 목뿐만 아니라
thoracic과 abdominal viscera에 innervation 함
• Cell body of sensory neurons : in ganglia
outside of the brain stem
• Cell body of motor : inside the brain stem
cranial nerve는 lower motor neuron
Three functions
• Supply motor innervation to muscles of the
face, eyes, tongue, jaw, and two neck
muscles (sternocleidomastoid and trapezius)
• Transmit somatosensory information from the
skin and muscles of the face and the
temporomandibular joint and special sensory
information related to visual, auditory,
vestibular, gustatory, olfactory and visceral
sensations
• Provide parasympathetic regulation of heart
rate, blood pressure, breathing and digestion
Olfactory N.
• Sensory
• Conduct from nasal chemoreceptors to
the olfactory bulb
• Olfactory bulb travel in the olfactory
tract to the medial temporal lobe of the
cerebrum
• The sense of smell
임상적 고찰
• Anosmia:
– 냄새를 맡지 못하는 증상으로 후각신경과 신
경로의 이상으로 생길수 있음
– heavy smoking, rhinitis, head injury,
olfactory groove meningioma, malingering
• Olfactory hallucination:
– uncinate seizure, senile dementia
• Loss of olfactory discrimination
Optic N.
• Sensory
• Transmit visual information from retina to the lateral
geniculate body of the thalamus and to nuclei in the
midbrain
• Optic n. projects from the retina to the midbrain and
to the lateral geniculate body of the thalamus
• The visual signals sent to the midbrain are involved in
reflexive responses of the pupil, awareness of light
and dark and orienting the head and eyes
• Reflex connections in the midbrain control the
constriction of the pupil and reflexive eye movements
• Visual information relayed by the lateral geniculate to
the visual cortex provides conscious vision
Cranial nerve reflex
• Pupillary : pupil of eye contricts when
light is shined into eye
• Consensual : pupil of eye constricts
when light is shined into other eye
• Accommodation : lens of eye adjusts to
focus light on the retina, pupil
constricts, and pupils move medially
when viewing an object at close range
• Masseter: when masseter is tapped with
a reflex hammer, the muscle contracts
• Corena : When the corena is touched,
the eyelids close
• Gag : touching of pharynx elicits
contraction of pharyngeal muscles
• Swallowing : food touching entrance of
pharynx elicits movements of the soft
palate and contraction of muscles of
the pharynx
임상적 고찰
• Ipsilateral blindness
• Loss of the pupillary light reflex
• Non-neurologic causes of reduced vision : cornea,
anterior chamber, lens, vitreous, retina
• Neurologic cause of reduced vision :
papilledema, syndrome of retrobulbar neuropathy,
toxic and nutritional optic neuropathy(tobaccoalcohol amblyopia, vit.B12 deficiency
• Others : chiasmal and optic nerve compression,
orbital inflammatory disease
Oculomotor, trochlear, and
abducens N.
• motor
• Move the eye (6 extraocular muscles)
• Control reflexive constriction of the
pupil
– four straight(rectus) muscles
– two oblique muscles
• If the eye is adducted, the superior
oblique depresses the eye, and the
inferior oblique elevate it
control of eye movement
• III
– control the superior, inferior, and medial rectus,
the inferior oblique, and the levator palpebrae
superioris m.
– move the eye upward, downward, and medially;
rotate the eye around the axis of the pupil; assist
in elevating the upper eyelid
• IV
– controls the superior oblique m. which rotates the
eye or if the eye is adducted, depress the eye
• VI
– controls the lateral rectus m. which moves the eye
laterally
Coordination of Eye movement
• Maintain via synergistic action of the eye
muscles
• To look toward the right, the abducens nerve
activates the lateral rectus to move the right
eye laterally, while the oculomotor nerve
activates the medial rectus to move the left
eye medially
• Eye and head movements are coordinated by
signals in the medial longitudinal fasciculus
Parasympathetic fibers of cranial nerve III
• Cranial N. III is involved in reflexive
constriction of the pupil and the muscles
controlling the lens of the eye
• The parasympathetic connections innervate
the intrinsic muscles of the eye (pupillary
spincter and cillary muscle)
• When the pupillary sphincter constricts, the
amout of light reaching the retina is
decreased
• When viewing objects closer than 20
centimeters, the ciliary muscles contracts,
increasing the curvature of the lens
accomodation
Pupillary, consensual and
accomodation reflexes
- The optic and oculomotor nerves
- The optic nerve is the afferent limb of
these reflexes, while the oculomotor
nerve provide the efferent limb
Eye reflexs
• Optic N
– retina  pretectal nucleus 
parasympathetic nuclei  ciliary ganglion
 pupillary sphincter
• The size of the pupil and the shape of
the lens of the eye
– reflexively controlled by afferents in the
optic N. and parasympathetic efferents in
the oculomotor N.
임상적 고찰
1)Oculomotor nerve palsy : ptosis, mydriasis,
inferolateral deviation of eye ball
**ptosis : 3rd nerve lesion, myasthenia gravis,
muscular dystrophy
- Ptosis(drooping of the eyelid) : paralysis of the
voluntary muscle fibers
- Diplopia(double vision)
- Deficit in moving the ipsilateral eye medially,
downward, and upward
- Loss of pupillary reflex and consensual response to
light
- Loss of constriction of the pupil in response to
focusing on a near object
2)Trochlear nerve palsy:
– hypertrophia, head-tilting or difficult to go
down stairs
– Prevents activation of the superior oblique
m. so cannot look downward and inward
3)Abducens nerve palsy
– Esotrophia, horizontal diplopia, paralysis of
outward movement
4)Common signs of ocular motor palsy
– diplopia
5)Cause of 3rd, 4th, 6th nerve palsy
– 3rd nerve : brain stem, tumor at the base of
the brain, trauma, ischemia, aneurysm of
the circle of wills, inflammation,
ophthalamoplegic migraine, idiopathic, etc
– 6th nerve : most common, neoplasm (adult:
nasopharyngeal cancer, children: pontine
glioma), inflammation, basal skull fracture
– 4th nerve : trauma
6)Acute bilateral ophalmoplegia
– brain stem (wernikes disease, pretectal infection)
– cranial nerves (guilliane-barre syndrome,
meningitis)
– Myoneural junction (myasthesia, botulism)
7)Chronic development of bilateral
ophthalmoplegia
– Ocular myopathy
8)Paralysis of conjugation: brain stem lesion
9)Pupillary change:
- 3rd nerve palsy
- Honor syndrome
- Argyll-Roberstson pupil
Trigeminal N.
• Sensory and motor
• Sensory fiber: transmit information from
the face and temporomandibular joint
• Motor fiber : innervate the muscle of
mastication
• Three branch : opthalmic, maxillary, and
mandibular
• Convey somatosensory signals
• Somatosensory information from the
face is conveyed by the trigeminal nerve
and distributed to the three trigeminal
nuclei :
−mesencephalic(proprioceptive)
−main sensory(discriminative touch)
−spinal(fast pain and temperature)
**Slow pain information projects to the
reticular formation
Pathway-chewing
• Discrimininative touch
– trigeminal ganglion main sensory
nucleus ventral posteromedial
somatosensory cortex
• Proprioception
– mesencephalic nucleus reticular
formation  unkwown
• Fast pain
– trigeminal ganglion spinal trigeminal
nucleus  ventral posteromedial nucleus
of thalamus  somatosensory cortex
• Slow pain
– trigeminal ganglion reticular formation 
reticular formation and intralaminar nuclei
 limbic system and throughout cortex
• Opthalamic fibers of the trigeminal N.
– cornea reflex
– (when cornea is touched) trigeminal nuclei
 interneuron  facial nerve (close eyelids
of both eyes)
• Masseter reflex
임상적 고찰
•
•
•
•
•
얼굴감각소실
고막긴장근의 마비로 인한 청력저하
씹기 근육마비로 손상된 쪽 아래턱의 쳐짐
입벌림 장애(trismus)
씹기근의 강직성 경련
– Trigeminal neuralgia : dysfunction of the
trigeminal N, producing severe, sharp,
stabbing pain
Trigeminal neuralgia
• A peripheral lesion leading to segmental
demyelination of the nerve, ephaptic
transmission, and subsequent secondary
changes in the spinal trigeminal nucleus
• Hyperexcitability of damaged fibers in the
trigeminal root ganglia, leading to
spontaneous neuronal firing
• Pressure of a blood vessel on the nerve
Facial N.
• Sensory and motor N.
• Sensory fibers
– transmit touch, pain, and pressure
information from the tongue and pharynx
and information from the chemoreceptors
located in the taste buds of the anterior
tongue to the solitary nucleus
• Motor innervation by the facial nerve
– close the eyes, move the lips, produce
facial expressions
• The trigeminal nerve provides the
afferent information from the cornea,
and the facial nerve activates eyelid
closure
• The facial N. innervates salivary, nasal,
and lacrimal (tear-producing) glands.
• The facial nerve innervates the muscles
of facial expression and most glands in
the head. It also conveys sensory
information from the oral region
임상적 고찰
• 말초성 얼굴신경마비(Bell’s palsy)
–
–
–
–
당뇨병의 합병증
종양
유사육종병(sarcoidosis)
AIDS
• 눈을 감으려고 하면 손상된 쪽의 눈동자가 위쪽
으로 향하는 Bell 현상이 나타남
• 말초 쪽에 병변이 있으면 손상이 있는 쪽의 얼굴
근육이 늘어지는 이완성 마비(flaccid paralysis)
– 칼로 인한 상처, 볼거리, 귀밑샘의 종창
Bell’s palsy
• Pathology
– paralysis of the muscles innervated by the facial
nerve on one side of the face
• Etiology: unknown
• Speed of onset: acute
• Signs and symptoms
– 의식, 대화 및 기억, 감각의 경우 정상이고 운동기능
에서는 한쪽 반이 마비 됨
• 남자와 여자가 같은 비율
• 예후: 80%가 2달 안에 회복되나 완전한 회복에
서 영구적인 마비까지 다양함
Vesibulocochlear N.
• Sensory nerve
• Two branch (vestibular , cochlear branch)
• Vestibular : transmit information related to head
position and head movements
• Cochlear : transmit information related to hearing
• Auditory information
– orients the head and eyes toward sounds
– increases the activity level throughout the central nervous
system
– Provides conscious awarness and recognition of sounds
– Cochelar nuclei : reticular formation-inferior colliculus
directly and via the superior olive-medial geniculate body
• Vestibular system
– 발의 자세, 몸 자세의 유지, 눈과 머리 및 몸
운동의 조절, 시각고정
– 머리의 위치와 머리의 회전에 대한 정보를 전
달
• 머리의 위치 : static information
• 머리의 회전 : dynamic information
임상적 고찰
• Deafness
– Conductive deafness : transmission of vibration is
prevented in the outer or middle ear(excessive in
the outer ear canal or otitis media, inflammation in
the middle ear)
– Sensorineural deafness : damage of the receptor
cells or the cochlear nerve(ototoxic drugs,
acoustic neuroma, tinnitus)
• Loss of hearing
Glossopharyngeal N.
• Sensory and motor fibers
• Sensory fibers
– transmit somatosensation from the soft
palate and pharynx and information from
chemoreceptor in the posterior
• Motor component
– innervates a pharyngeal muscle and the
parotid salivary gland
• Glossopharyngeal sensory fibers
contribute the afferent limb of the gag
reflex spinal nucleus ambigus
nucleus
• Cause the pharyngeal muscles to
contract
• Provide the afferents limb of the gag
and swallowing reflexes, supplies taste
information, and innervates a salivary
gland
임상적 고찰
• Gag reflex
– 인두로부터 오는 혀인두신경
(glossopharyngeal N.) 의 감각성분에 의해서
일어나고 이에 대한 구토반응은 미주신경
(vagus N.)
•
•
•
•
Swallowing reflex
Salivation decrease
Glossopharyngeal neuralgia
Soft palate weakness and dysphagia
Vagus N.
• Provides afferent and efferent innervation of
the larynx, pharynx, and viscera
• Regulate viscera, swallowing, and speech
• Supplies taste information
• Decrease heart rate, constrict the bronchi,
affect speech production, and increase
digestive activity
• Elicit the gag reflex (motor function)
임상적 고찰
• Difficulty speaking, swallowing, poor
digestion due to decreased digestive
enzymes
• Decreased peristalsis
• Asymmetrical elevation of the palate
• hoarseness
Accessory N.
• Motor
• Innervation to the trapezius and sternocleidomastoid
muscles
• Cell bodies
– in the ventral horn at levels C1 to C4
• Accessory N. originates in the spinal accessory
nucleus in the upper cervical cord, travels upward
through the foramen magnum, then leaves the skull
through the jugular foramen
• 임상적 고찰
– shoulder drop, weakness when turning head to opposite side,
scapular winging
Hypoglossal N.
• Motor
• Provide innervation to the intrinsic and
extrinsic muscles of the ipsilateral tongue
• Cell body
– hypoglossal nucleus of the medulla
• Controlled by both voluntary and reflexive
neural circuits
• 임상적 고찰
– Tongue deviation
– Difficulty speaking and swallowing
Cranial N. involved in
swallowing and speaking
Speaking
•
•
•
•
•
Sounds generated by the larynx(X) :
Soft palate(X)
Lips(VII)
Jaws(V)
Tongue(XII)