bbs ii slide the cranial nerves spinal nerves

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

Classification of cranial nerves

• Sensory cranial nerves: contain only afferent (sensory) fibers

– Ⅰ_ⅠⅠⅠOlfactory nerve – ⅡⅡⅡⅡOptic nerve

– Ⅷ_ⅧⅧⅧVestibulocochlear nerve

• Motor cranial nerves: contain only efferent (motor) fibers

– Ⅲ_ⅢⅢⅢOculomotor nerve – Ⅳ_ⅣⅣⅣTrochlear 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

Ⅱ Ganglion cells (SSA) Optic canal Lateral geniculate Vision

Olfactory nerve

Olfactory mucosa (SVA)→ Cribriform foramina → Olfactory bulb

Optic nerve

Ganglion cell (SSA)→ Optic canal → Lateral geniculate body

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

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

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

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

•

Skin between eye 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

postganglionic fibers supply lacrimal, submandibular and sublingual glands

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

•

Submandibular ganglion

: lies between lingual nerve and

submandibular gland

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

• SVAfibers: 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

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

•

SVE

fibers: originate from ambiguus, to muscles of

pharynx and larynx

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

cricothyroid joint, the nerve is now called inferior laryngeal nerve

• 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

Contains both sensory and motor neurons that innervate the dorsal

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

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

•

Sensory: From skin along lateral

surface of forearm

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

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

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

•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.

• Common fibular nerve is susceptible to injury because of its superficial location at the head

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

•

Polysynaptic reflex

arc

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.

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)

30

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 dorsiflexthe 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

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

32

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

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

34

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.