The Cranial Nerves &
Spinal nerves
Departemen Anatomi
Fakultas Kedokteran
USU
Names of cranial nerves
Classification of cranial nerves
• Sensory cranial nerves: contain only afferent (sensory) fibers
– ⅠⅠⅠⅠOlfactory nerve – ⅡⅡⅡⅡOptic nerve
– ⅧⅧⅧⅧVestibulocochlear nerve
• Motor cranial nerves: contain only efferent (motor) fibers
– ⅢⅢⅢⅢOculomotor nerve – ⅣⅣⅣⅣTrochlear nerve – ⅥⅥⅥⅥAbducent nerve – ⅪⅪⅪⅪAccessory nerv – ⅫⅫⅫⅫHypoglossal nerve
• Mixed nerves: contain both sensory and motor
fibers---– ⅤⅤⅤⅤTrigeminal nerve,
– ⅦⅦⅦⅦFacial nerve,
– ⅨⅨⅨⅨGlossopharyngeal nerve
– ⅩⅩⅩⅩVagus nerve
Sensory cranial nerves
N. Location of cell body and axon categories Cranial exit Terminal nuclei Main action Ⅰ ⅠⅠ
Ⅰ Olfactory cells (SVA) Cribrifom foramina Olfactory bulb Smell Ⅱ ⅡⅡ
Olfactory nerve
Olfactory mucosa (SVA)→ Cribriform foramina → Olfactory bulb
Vestibulocochlear nerve
Vestibular 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 action
Ⅲ ⅢⅢ
Ⅲ 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 muscl
Ⅳ ⅣⅣ
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
Abducent nerve
Accessory nerve
Oculamotor paralysis
Abducent nerve injury
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
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
Maxillary nerve
(
Ⅴ
2,
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
Mandibular nerve
(
Ⅴ
3, mixed)
•
Leave the skull through the
foramen
ovale
to enter the infratemporal
fossa
•
Branches
– Auriculotemporal nerve
– Buccal nerve
– Lingual nerve
– Inferior alveolar nerve
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 (
Ⅶ
Ⅶ
Ⅶ
Ⅶ
)
Components of fibers
• SVEfibers originate from nucleus of facial nerve, and supply facial muscles
• GVEfibers derived from superior salivatory nucleus and relayed in pterygopalatine ganglion and submandibular ganglion. The
Course
: leaves skull through
internal acoustic meatus,
facial canal and
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
Branches outside of facial canal
•
Temporal
•
Zygomatic
•
Buccal
•
Marginal mandibular
•
Cervical
•
Pterygopalatine ganglion
: lies in pterygopalatine fossa
under maxillary nerve
Injury to the facial nerve
Glossopharyngeal nerve (
Ⅸ
Ⅸ
Ⅸ
Ⅸ
)
Components of fibers
• SVE fibers: originate from nucleus ambiguus, and supply stylopharygeus
• GVEfibers: arise from inferior salivatory nucleus and ralyed in otic ganglion, the postganglionic fibers supply parotid gland
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
Vagus nerve (
Ⅹ
Ⅹ
Ⅹ
Ⅹ
)
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
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
• 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
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
• 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
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 roots
that attach the nerve to the s.c. Laterally, give rise to the rami
that innervate the dorsal and ventral regions of the body
Dorsal ramus
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
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
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
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)
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)
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
•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 dorsiflexthe foot-Tibialis anterior, EDL, EHL)
– Sensory: From skin of the lateral and anterior leg and dorsum of the foot.
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
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
Stretch Reflex
Flexor Withdrawal Reflexes
•
Occurs during
withdrawal of foot
from pain
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.
