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The Cranial & Spinal nerves

Departemen Anatomi Fakultas Kedokteran USU

Names of • Ⅰ Olfactory • Ⅱ • Ⅲ • Ⅳ • Ⅴ • Ⅵ Abducent nerve • Ⅶ • Ⅷ • Ⅸ Glossopharyngeal nerve • Ⅹ • Ⅺ • Ⅻ

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Classification of cranial nerves

• Sensory cranial nerves : contain only afferent (sensory) fibers – ⅠⅠⅠ – ⅡⅡⅡOptic nerve – ⅧⅧⅧ Vestibulocochlear nerve • Motor cranial nerves : contain only efferent (motor) fibers – ⅢⅢⅢ Oculomotor nerve – ⅣⅣⅣ Trochlear nerve – ⅥⅥⅥAbducent nerve – ⅪⅪⅪ Accessory nerv – ⅫⅫⅫ Hypoglossal nerve • Mixed nerves : contain both sensory and motor fibers--- – ⅤⅤⅤTrigeminal nerve, – ⅦⅦⅦ Facial nerve, – ⅨⅨⅨGlossopharyngeal nerve – ⅩⅩⅩVagus nerve

Sensory cranial nerves

N. Location of cell Cranial Terminal Main body and axon exit nuclei action categories ⅠⅠⅠ Olfactory cells Cribrifom Olfactory Smell (SVA) foramina bulb ⅡⅡⅡ Ganglion cells Optic Lateral Vision (SSA) canal geniculate body ⅧⅧⅧ Vestibular Internal Vestibular Equilibri ganglion(SSA) acoustic nuclei um meatus Cochlear Cochlear Hearing ganglion (SSA) nuclei

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Olfactory nerve

Olfactory mucosa (SVA) → Cribriform foramina →

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

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

Motor cranial nerves

N. Nucleus of origin and Cranial exit Main action axon categories ⅢⅢⅢ Nucleus of oculomotor Superior orbital Motot to superior, inferior (GSE) fissure and medial recti; inferior obliquus; levator palpebrae superioris Accessory nucleus of Parasympathetic to oculomotor (GVE) sphincter pupillea and ciliary muscl ⅣⅣⅣ Nucleus of trochlear Superior orbital Motor to superior obliquus nerve (GSE) fissure ⅥⅥⅥ Nucleus of abducent Superior orbital Motor to lateral rectus nerve (GSE) fissure ⅪⅪⅪ Nucleus of accessory Jugular foramen Motor to nerve (SVE) sternocleidomastoid and trapezius ⅫⅫⅫ Nucleus of hypoglossal Hypoglossal canal Motot to muscles of nerve( GSE) 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 • : lies between optic nerve and lateral rectus

Oculomotor nerve

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Accessory nerve

Abducent 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 , which lies on the apex of petrous part of temporal bone

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Branches • (Ⅴ1, sensory) leave the skull through the superior orbital fissure, to enter orbital cavity • Branches – : • • – –

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 – – – 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 – – – – – 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 ( Ⅶ) 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 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 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, 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 • : joins lingual branch of – To taste buds on anterior two-thirds of tongue – Relayed in submandibular ganglion, the postganglionic fibers supply submandibular and sublingual glands

• : 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 under • Submandibular ganglion : lies between lingual nerve and

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Injury to the facial nerve

Glossopharyngeal nerve ( Ⅸ) Components of fibers • SVE fibers: originate from , and supply stylopharygeus • GVE fibers: arise from inferior salivatory nucleus and ralyed in , 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 ( 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 • GVA fibers: carry impulse from viscera in , 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 • Forms posterior vagal trunk at esophageal hiatus where it leaves 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 • : 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

Internal branch

External 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 • 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 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 regions of the body › Ventral ramus  Contains both sensory and motor neurons that innervate the ventral regions of the body  Braid together to form plexus es (plexi)

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• Dorsal Ramus : innervate deep muscles of the trunk Branches of responsible for movements of the vertebral Spinal Nerves 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 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.

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