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The Cranial Nerves &
Spinal nerves
Departemen Anatomi
Fakultas Kedokteran
USU
Names of cranial nerves• Ⅰ Olfactory nerve
• Ⅱ Optic nerve
• Ⅲ Oculomotor nerve
• Ⅳ Trochlear nerve
• Ⅴ Trigeminal nerve
• Ⅵ Abducent nerve
• Ⅶ Facial nerve
• Ⅷ Vestibulocochlear nerve
• Ⅸ Glossopharyngeal nerve
• Ⅹ Vagus nerve
• Ⅺ Accessory nerve
• Ⅻ Hypoglossal nerve
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Classification of cranial nerves
• Sensory cranial nerves: contain only afferent (sensory) fibers
– ⅠⅠⅠⅠOlfactory nerve
– ⅡⅡⅡⅡOptic nerve
– ⅧⅧⅧⅧ Vestibulocochlear nerve
• Motor cranial nerves: contain only efferent (motor) fibers
– ⅢⅢⅢⅢ Oculomotor nerve
– ⅣⅣⅣⅣ Trochlear nerve
– ⅥⅥⅥⅥAbducent nerve
– ⅪⅪⅪⅪ Accessory nerv
– ⅫⅫⅫⅫ Hypoglossal nerve
• Mixed nerves: contain both sensory and motor fibers---
– ⅤⅤⅤⅤTrigeminal nerve,
– ⅦⅦⅦⅦ Facial nerve,
– ⅨⅨⅨⅨGlossopharyngeal nerve
– ⅩⅩⅩⅩVagus nerve
Sensory cranial nerves
N. Location of cell body and axon categories
Cranial exit
Terminal nuclei
Main actionⅠⅠⅠⅠ Olfactory cells
(SVA)Cribrifomforamina
Olfactory bulb
Smell ⅡⅡⅡⅡ Ganglion cells (SSA)
Optic canal
Lateral geniculate body
Vision ⅧⅧⅧⅧ Vestibular ganglion(SSA)
Internal acoustic meatus
Vestibular nuclei
Equilibrium
Cochlear ganglion (SSA)
Cochlear nuclei
Hearing
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Olfactory nerve
Olfactory mucosa (SVA)→ Cribriform foramina → Olfactory bulb
Optic nerveGanglion cell (SSA) → Optic canal → Lateral geniculate body
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Vestibulocochlear nerveVestibular ganglion(SSA) ↘↘↘↘ ↗↗↗↗ Vestibular nuclei
Internal acoustic meatus
Cochlear ganglion (SSA) ↗↗↗↗ ↘↘↘↘ Cochlear nuclei
Motor cranial nerves
N. Nucleus of origin and axon categories
Cranial exit Main actionⅢⅢⅢⅢ Nucleus of oculomotor (GSE)
Superior orbital fissure
Motot to superior, inferior and medial recti; inferior obliquus; levator palpebrae superioris
Accessory nucleus of oculomotor (GVE)
Parasympathetic to sphincter pupillea and ciliary musclⅣⅣⅣⅣ Nucleus of trochlear
nerve (GSE)Superior orbital fissure
Motor to superior obliquusⅥⅥⅥⅥ Nucleus of abducent nerve (GSE)
Superior orbital fissure
Motor to lateral rectus ⅪⅪⅪⅪ Nucleus of accessory nerve (SVE)
Jugular foramen Motor to sternocleidomastoid and trapeziusⅫⅫⅫⅫ Nucleus of hypoglossal
nerve( GSE)Hypoglossal canal Motot to muscles of
tongue
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Oculomotor nerve• Components
– General somatic efferent fibers (GSE)
– General visceral efferent fibers (GVE)
• Main action－－－－supplies
– Superior, inferior and medial recti; inferior obliquus; levator palpebrae superioris
– Sphincter pupillea and ciliary muscle
• Ciliary ganglion: lies between optic nerve and lateral rectus
Oculomotor nerve
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Abducent nerve
Accessory nerve
Hypoglossal nerve
Hypoglossal nerve
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Oculamotor paralysis
Abducent nerve injury
Mixed cranial nerves
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Trigeminal nerve
Components of fibers
• SVE fibers: originate from motor nucleus of trigeminal nerve, and supply masticatory muscles
• GSA fibers: transmit facial sensation to sensory nuclei of trigeminal nerve, the GSA fibers have their cell bodies in trigeminal ganglion, which lies on the apex of petrous part of temporal bone
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Branches
• Ophthalmic nerve (Ⅴ1,
sensory) leave the skull
through the superior orbital
fissure, to enter orbital
cavity
• Branches
– Frontal nerve:
• Supratrochlear nerve
• Supraorbital nerve
– Lacrimal nerve
– Nasociliary nerve
Distribution:
• Sensation from cerebral
dura mater
• Visual organ
• Mucosa of nose
• Skin above the eye and
back of nose
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Maxillary nerve (Ⅴ2,
sensory)
• Leave skull through
foramen rotundum
• Branches
– Infraorbital nerve
– Zygomatic nerve
– Superior alveolar nerve
– Pterygopalatine nerve
Distribution:
• Sensation from cerebral dura mater
• Maxillary teeth
• Mucosa of nose and mouth
• Skin between eye and mouth
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Mandibular nerve (Ⅴ3, mixed)
• Leave the skull through the foramen
ovale to enter the infratemporal
fossa
• Branches
– Auriculotemporal nerve
– Buccal nerve
– Lingual nerve
– Inferior alveolar nerve
– Nerve of masticatory muscles
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Distribution:
• Sensation from cerebral dura
mater
• Teeth and gum of lower jaw
• Mucosa of floor of mouth
• Anterior 2/3 of tongue
• Skin of auricular and temporal
regions and below the mouth
• Motor to masticatory muscles,
mylohyoid, and anterior belly
of digastric
Facial nerve (ⅦⅦⅦⅦ)Components of fibers
• SVE fibers originate from nucleus of facial nerve, and supply facial
muscles
• GVE fibers derived from superior salivatory nucleus and relayed in
pterygopalatine ganglion and submandibular ganglion. The
postganglionic fibers supply lacrimal, submandibular and sublingual
glands
• SVA fiber from taste buds of anterior two-thirds of tongue which cell
bodies are in the geniculate ganglion of the facial nerve and end by
synapsing with cells of nucleus of solitary tract
• GSA fibers from skin of external ear
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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
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Branches within the facial canal
• Chorda tympani : joins lingual branch of mandibular nerve
– To taste buds on anterior two-thirds of tongue
– Relayed in submandibular ganglion, the postganglionic fibers supply submandibular
and sublingual glands
• Greater petrosal nerve : GVE fibers pass to pterygopalatine ganglion and
there relayed through the zygomatic and lacrimal nerves to lacrimal gland
• Stapedial nerve : to stapedius
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Branches outside of facial canal
• Temporal
• Zygomatic
• Buccal
• Marginal mandibular
• Cervical
• Pterygopalatine ganglion : lies in pterygopalatine fossa under maxillary nerve
• Submandibular ganglion : lies between lingual nerve and submandibular gland
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Injury to the facial nerve
Glossopharyngeal nerve (ⅨⅨⅨⅨ)
Components of fibers• SVE fibers: originate from nucleus ambiguus, and supply
stylopharygeus
• GVE fibers: arise from inferior salivatory nucleus and ralyed in otic ganglion, the postganglionic fibers supply parotid gland
• SVA fibers: arise from the cells of inferior ganglion, the central processes of these cells terminate in nucleus of solitary tract, the peripheral processes supply the taste buds on posterior third of tongue
• GVA fibers: visceral sensation from mucosa of posterior third of tongue, pharynx, auditory tube and tympanic cavity, carotid sinus and glomus, and end by synapsing with cells of nucleus of solitary tract
• GSA fibers: sensation from skin of posterior surface of auricle and
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Course: leaves the skull via jugular foramen
Branches
• Lingual branches : to taste buds and mucosa of posterior third of tongue
• Pharyngeal branches : take part in forming the pharyngeal plexus
• Tympanic nerve : GVE fibers via tympanic and lesser petrosal nerves to
otic ganglion, with postganglionic fibers via auriculotemporal (Ⅴ3) to
parotid gland
• Carotid sinus branch : innervations to both carotid sinus and glomus
• Others: tonsillar and stylophayngeal branches
Otic ganglion : situated just below foramen ovale
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Vagus nerve (ⅩⅩⅩⅩ)components of fibers
• GVE fibers: originate from dorsal nucleus of vagus nerve, synapse in parasympathetic ganglion, short postganglionic fibers innervate cardiac muscles, smooth muscles and glands of viscera
• SVE fibers: originate from ambiguus, to muscles of pharynx and larynx
• GVA fibers: carry impulse from viscera in neck, thoracic and abdominal cavity to nucleus of solitary tract
• GSA fiber: sensation from auricle, external acoustic meatus and cerebral dura mater
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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 vagus nerve
• 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
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Left vagus nerve
• Enter thoracic inlet between left common carotid
and left subclavian arteries, 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
Branches in neck
• Superior laryngeal nerve: passes down side of pharynx and given rise to
– Internal branch, which pierces thyrohyoid membrane to innervates mucous membrane of larynx above fissure of glottis
– External branch, which innervates cricothyroid
• Cervical cardiac branches : descending to terminate in cardiac plexus
• Others: auricular, pharyngeal and meningeal branches
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Superior laryngeal nerve
External branch
Internal branch
Branches in thorax
• Recurrent laryngeal nerves
– Right one hooks around right subclavian
artery, left one hooks aortic arch
– Both ascend in tracheo-esophageal groove
– Nerves enter larynx posterior to
cricothyroid joint, the nerve is now called
inferior laryngeal nerve
– Innervations: laryngeal mucosa below
fissure of glottis , all laryngeal laryngeal
muscles except cricothyroid
• Bronchial and esophageal branches
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Branches in abdomen
• Anterior and posterior gastric branches
– Run close to lesser curvature and innervate anterior and posterior surfaces of stomach
– As far as pyloric antrum to fan out into branches in a way like the digits of a crow’s foot to supply pyloric part
• Hepatic branches: join hepatic plexus and then supply liver and gallbladder
• Celiac branches: send branches to celiac plexus to be distributed with sympathetic fibers to liver, pancreas, spleen, kidneys, intestine as far as left colic flexure
Spinal Nerves
� Thirty-one pairs of spinal nerves
� First pair exit vertebral column between skull and atlas (C1)
� Last four pair exit via the sacral foramina
� Others exit through intervertebral foramina
� Eight pair cervical, twelve pair thoracic, five pair lumbar, five pair sacral, one pair coccygeal
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Dermatomal Map� Spinal nerves indicated by capital letter and number
� Dermatomal map: skin area supplied with sensory innervation by spinal nerves
Spinal Nerves
� Medially, give rise to the rootsthat attach the nerve to the s.c.
� Laterally, give rise to the ramithat innervate the dorsal and ventral regions of the body
› Dorsal ramus
� Contains both sensory and motor neurons that innervate the dorsal regions of the body
› Ventral ramus
� Contains both sensory and motor neurons that innervate the ventral regions of the body
� Braid together to form plexuses (plexi)
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Branches of
Spinal Nerves
• Dorsal Ramus: innervate deep muscles of the trunk responsible for movements of the vertebral column and the C.T. and skin near the midline of the back.
• Ventral Ramus: what they innervate depends upon which part of the spinal cord is considered.
– Thoracic region: form intercostal nerves that innervate the intercostal muscles and the skin over the thorax
– Remaining spinal nerve ventral rami form five plexuses (intermingling of nerves).
• Ventral rami of C1-C4= cervical plexus
• Ventral rami of C5-T1= brachial plexus
• Ventral rami of L1-L4= lumbar plexus
• Ventral rami of L4-S4= sacral plexus
• Ventral rami of S4 and S5= coccygeal plexus
• Communicating Rami: communicate with sympathetic chain of ganglia.
Cervical Plexus
• Formed by ventral rami of spinal nerves C1-C4
• Motor: Innervates muscles of the neck (SCM, trapezius), laryngeal muscles
• Sensory: Skin of upper chest, shoulder, neck, and ear
• Phrenic nerve
– From C3-C5 (cervical and brachial plexuses)
– Innervates diaphragm
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Brachial Plexus
• Formed by ventral rami of spinal nerves C5-T1
• Five ventral rami form three trunks that separate into six divisions then form cords that give rise to: (RTDC)
• Branches/nerves
– Axillary
– Radial
– Musculocutaneous
– Ulnar
– Median
Brachial Plexus: Axillary Nerve
• Motor: Innervates deltoid and
teres minor
– Deltoid - Abducts arm
– Teres - Laterally rotate arm
• Sensory: from skin of the lateral
shoulder
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Brachial Plexus: Radial Nerve
• Motor: Stimulates extensor muscles of arm, forearm, and hand
– Triceps, supinator, brachioradialis, ECR, ECU, and some extensors of the fingers (extensor digitorum)
– Cause extension movements at elbow and wrist, thumb movements
• Sensory: From skin on posterior surface of arm and forearm, lateral 2/3 of dorsum of hand
• Damage due to compression results in crutch paralysis
• Major symptom is ‘wrist drop’
– Failure of extensors of wrist and fingers to function
– Elbow, wrist, and fingers constantly flexed
Brachial Plexus:
Musculocutaneous Nerve
• Motor: Stimulates flexors in
anterior arm: (biceps brachii,
brachialis)
– Causes flexion movements at
shoulder and elbow
• Sensory: From skin along lateral
surface of forearm
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Brachial Plexus: Ulnar Nerve
• Motor: Stimulates flexor
muscles in anterior forearm
(FCU, FDP, most intrinsic
muscles of hand)
– Results in wrist and finger
flexion
• Sensory: From skin on medial
surface of hand, little finger,
and medial surface of ring
finger
• Most easily damaged
– Hitting the “funny bone” excites
it
Brachial Plexus: Median Nerve
� Motor: Innervates all but one of the flexors of the wrist and fingers, and thenar muscles at base of thumb (Palmaris longus, FCR, FDS, FPL, pronator)
› Causes flexion of the wrist and fingers and thumb
� Sensory: From skin of anterolateral 2/3 palm, thumb, index and middle fingers; lateral surface of ring finger
� Damaged in carpal tunnel and suicide attempts
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Lumbosacral Plexus� Lumbar plexus: formed by
ventral rami of spinal nerves L1-L4
� Sacral plexus: formed by ventral rami of L4-S4
� Usually considered together because of their close relationship
� Four major nerves exit and enter lower limb› Obturator
› Femoral
› Tibial
› Common fibular (peroneal)
Lumbar Plexus:Obturator Nerve
• Motor: Innervates adductor
group and gracilis
– Causes adduction of the thigh
and knee (gracilis)
• Sensory: From skin of the
superior medial side of
thigh
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Lumbar Plexus: Femoral Nerve• Motor:
– Innervates anterior muscles of
thigh
• Quadriceps group and sartorius
• Cause extension of the knee
– Innervates flexors and
adductors of hip: Pectineus and
Iliopsoas
• Cause flexion of the hip
• Sensory: From skin of the
anterior and lateral thigh;
medial surface of leg and foot
Sacral Plexus: Sciatic Nerve• Thickest and longest nerve of the body
• Innervates posterior thigh and entire lower leg
• Composed of 2 nerves (tibial n. and common fibular nerve (or peroneal nerve) in a common sheath)
– Leaves pelvis via greater sciatic notch
– Courses deep to gluteus and enters posterior thigh just medial to the hip joint
• The 2 divisions diverge just above the knee.
• Sciatic Nerve Injury• May be due to fall, disc herniation, impro-per
administration of injection into buttock• When transected, leg is nearly useless• Leg cannot be flexed (hamstrings
paralyzed)• All foot and ankle movement is lost• Foot drops into plantar flexion (footdrop)
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Tibial Nerve
•Tibial– Innervates muscles of:
– Posterior thigh -hamstrings
(knee flexors, hip extensors)
– Posterior leg(gastrocnemius, -plantar flexors; FDL, FHL - toe flexors)
– Branches in foot to form medial and lateral plantar nerves
• Tibial nerve injury, paralyzed calf
muscles
- cannot plantar flex foot;shuffling
gait develops
Common Fibular (Peroneal) Nerve
• Common Fibular Nerve
– Innervates anterior and lateral muscles of the leg and foot
• Extensors that dorsiflex the foot-Tibialis anterior, EDL, EHL)
– Sensory: From skin of the lateral and anterior leg and dorsum of the foot.
• Common fibular nerve is susceptible to injury
because of its superficial location at the head
and neck of the fibula.
– Tight leg cast, remaining too long in a side-
lying position on a firm mattress may
compress this nerve and result in
footdrop
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Other Nerves of the Lumbosacral Plexus
• Nerves that innervate the skin of the suprapubic area, external genitalia, superior medial thigh, posterior thigh
– Iliohypogastric nerve - Muscles of abdominal wall and pubic region
– Genitofemoral nerve - Skin of scrotum (males) and labia (females); inferior abdominal muscles
– Pudendal nerve - innervates muscles and skin of the perineum (region encompasssing external genitalia and anus); external anal sphincter; mediates erection, and is involved in voluntary control of urination; the “shameful” nerve
Coccygeal Plexus
• S4-S5; coccygeal nerve
• Muscles of pelvic floor
• Sensory information from skin over coccyx
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Nature of Somatic Reflexes
• Quick, involuntary, stereotyped reactions of glands or muscle to sensory stimulation
– automatic responses to sensory input that occur without our intent or often even our awareness
• Functions by means of a somatic reflex arc
– stimulation of somatic receptors
– afferent fibers carry signal to dorsal horn of spinal cord
– one or more interneurons integrate the information
– efferent fibers carry impulses to skeletal muscles
– skeletal muscles respond
The Muscle Spindle
� Sense organ (proprioceptor) that monitors length of muscle and how fast muscles change in length
� Composed of intrafusal muscle fibers, afferent fibers and gamma motorneurons
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Stretch Reflex
Flexor Withdrawal Reflexes
• Occurs during withdrawal of foot from pain
• Polysynaptic reflex arc
• Neural circuitry in spinal cord controls sequence and duration of muscle contractions
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Crossed Extensor Reflexes
• Maintains balance by
extending other leg
• Intersegmental reflex extends
up and down the spinal cord
• Contralateral reflex arcs
explained by pain at one foot
causes muscle contraction in
other leg
Relationship of Brain and Spinal Cord
Reflexes
• Sensory information goes
to brain; e.g., pain.
• Descending tracts convey
motor impulses from
brain to effectors.
