HNS08 Cranial Nerves Flashcards
***12 pairs of cranial nerve
Sensory function only:
- Olfactory (CN1)
- Optic (CN2)
- Vestibulocochlear (CN8)
Motor function only:
- Oculomotor (CN3)
- Trochlear (CN4)
- Abducens (CN6)
- Accessory (CN11)
- Hypoglossal (CN12)
Both sensory and motor function:
- Trigeminal (CN5)
- Facial (CN7)
- Glossopharyngeal (CN9)
- Vagus (CN10)
Functional components of cranial nerves
Sensory
- General somatic sensory
- touch, pain, temperature, pressure, vibration, proprioception - General visceral sensory
- sensory input from the viscera (except pain) - Special sensory
- smell, vision, taste, hearing, balance
Motor
- General somatic motor
- innervates muscles that develop from somites - Branchial motor
- innervates muscles that develop from branchial (pharyngeal) arches (CN5,7,9,10,11) - General visceral motor
- innervates viscera (including glands and all smooth muscles)
Cranial nerve locations
See slide
Cranial nerve nuclei
Sensory nuclei:
- developed from Alar plate —> as 4th ventricle and brainstem expands —> more lateral
Motor nuclei:
- developed from Basal plate —> as 4th ventricle and brainstem expands —> more medial
CN1 Olfactory nerve
Olfactory system consist of:
- Olfactory epithelium
- Bulbs (belong to CNS)
- Tracts (belong to CNS)
- Olfactory areas of brain (collectively known as Rhinencephalon)
Peripheral processes of receptor cells —> small bundles
—> pass through Cribriform plate of ethmoid bone
—> synapse on secondary sensory neurons in Olfactory bulb (lie on Cribriform plate)
—> Olfactory bulb
—> Olfactory tract
—> Medial stria (terminates in anterior commissure to project to contralateral olfactory structure)
OR
—> Lateral stria (terminates in primary olfactory (piriform) cortex of the temporal lobe (ipsilateral))
Cells of origin:
***Bipolar cells in olfactory epithelium (special sensory)
Central connections (where cranial nerve neurons synapse in CNS): Olfactory bulb (location of secondary olfactory neurons)
Peripheral distribution:
Cilia at surface of olfactory epithelium in superior nasal concha + upper third of nasal septum
Function:
Smell
Signs of damage:
Anosmia (loss of smell sensation)
Primary olfactory receptor cells
- Bipolar nerve cells with a dendrite
—> terminates in a knob and project numerous cilia - Axons of olfactory neurons contact dendrites of secondary olfactory cells (Mitral cell + Tufted cell) in olfactory bulb
- Bipolar cells undergo continuous replacement throughout life
CN2 Optic nerve (part of CNS)
Arise from retina of eye
Image of visual field projected onto retina upside-down and reversed
—> **Photoreceptors (Cone, Rod cells) —> electrical signals
—> **Bipolar cells
—> **Retinal ganglion cells
—> Optic nerve (pass through optic canals —> converge at optic chiasm)
—> Optic chiasm
—> Optic tract (fibres continue posteriorly around midbrain with most synapsing in **lateral geniculate nucleus of their respective thalamus / small portion enter **pretectal region of midbrain and participate in pupillary light reflex)
—> **Lateral geniculate nuclei of Thalamus —> secondary neuron / optic radiation fibres
—> Visual cortex
Cells of origin:
Retinal ganglion cells (special sensory)
Central connections:
- Lateral geniculate nuclei (in Thalamus)
- Superior colliculus + pretectal nuclei (afferent pathway of pupillary light reflex)
Peripheral distribution:
Retinal bipolar cells
Function:
- Vision
- Pupillary light reflexes
Signs of damage:
- Blindness
- Absent of pupillary constriction bilaterally on testing blind eye
Projection of visual field to thalamus
Image on medial side of retina: Contralateral side of thalamus (cross at Optic chiasm)
Image on lateral side of retina: Ipsilateral side of thalamus at Lateral geniculate nuclei
Effect:
- Left side image perceived on Right side brain (vice versa)
Pupillary light reflex
Optic nerve
—> Pretectal nuclei
—> Project bilaterally to both side of Edinger-Westphal nuclei
—> through Oculomotor nerve
—> Ciliary ganglion
—> short ciliary nerves
—> direct + consensual pupillary constriction
CN3 Oculomotor nerve
- Emerges from medial side of midbrain, superior to pons
- Innervates all ***extraocular muscles except Superior oblique (CN4) and Lateral rectus (CN6) for precise movement of eyes, for visual tracking / fixation on object
- also supplies ***elevator of upper eyelid (Levator palpebrae superioris)
Cells of origin:
- Oculomotor nucleus (Somatic motor)
- Edinger-Westphal nucleus (Visceral motor)
Central connections:
NA (∵ nucleus already in CNS)
Peripheral distribution:
- Superior, Inferior, Medial rectus muscle; Inferior oblique; Levator palpebrae superioris (5 of 7 eye muscles)
- **Ciliary ganglion: postganglionic via short ciliary nerves to **sphincter of pupil + ***ciliary muscle
Function:
- Eye movement + elevates upper eyelid
- Contraction of pupil + Accommodation of lens
Signs of damage:
- Ophthalmoplegia with eye deviated down and out, severe ptosis (drooping eyelid)
- Mydriasis; loss of pupillary light and accommodation reflexes in ipsilateral eye
Accommodation reflex
Adaptation of visual apparatus to facilitate NEAR vision which involves:
- ↑ Curvature of lens by ciliary muscle contraction (↑ refractive power)
- Pupillary constriction to help sharpen image on retina
- Convergence of the eyes to fixate on target object
CN4 Trochlear nerve
Emerges from dorsal brainstem (already crossed)
Cells of origin:
- Trochlear nucleus (Somatic motor)
Central connections:
NA (∵ nucleus already in CNS)
Peripheral distribution:
- Superior oblique muscle (***Contralateral, but already crossed in midbrain)
Function:
- Intorsion (向內擰); Depression of adducted eye
Signs of damage:
- Diplopia (double vision), head tilt to unaffected side (∵眼向外擰,頭唯有向相反方向擺), weakness in depression of ipsilateral (∵ already crossed) adducted eye
CN6 Abducens nerve
Emerges from ventral medial brainstem, between pons and medulla oblongata
Cells of origin:
- Abducens nucleus (Somatic motor)
Central connections:
NA (∵ nucleus already in CNS)
Peripheral distribution:
- Lateral rectus muscle
Function:
- Abduction of eye (向外望)
Signs of damage:
- Diplopia, medial deviation, inability to abduct affected eye
CN5 Trigeminal nerve
Emerges from lateral pons
3 divisions for ***general sensation towards Trigeminal ganglion (innervates different parts of face / forehead):
- Ophthalmic division (V1) —> sensory ONLY
- Maxillary division (V2) —> sensory ONLY
- Mandibular division (V3) —> sensory + motor
4 nuclei:
- Pontine trigeminal nucleus (sensory)
- Spinal trigeminal nucleus (sensory)
- Mesencephalic trigeminal nucleus (sensory)
- Trigeminal motor nucleus (motor)
Cells of origin:
- Trigeminal ganglion (General sensory) —> Somatosensations
- Mesencephalic trigeminal nucleus (General sensory) —> Proprioceptive reflexes
- Trigeminal motor nucleus (Branchial motor) —> Mastication
Central connections:
- Spinal trigeminal nucleus (caudal part) + Pontine trigeminal nucleus
- NA
- NA
Peripheral distribution:
- Ophthalmic (V1), Maxillary (V2), Mandibular (V3) divisions to mucous membranes and skin of face and head
- Muscles of mastication, peridontal membrane, temporomandibular joint, external ocular muscle
- Temporalis, masseter, lateral and medial pterygoids + tensor veli palatini and tensor tympani, anterior belly of digastric, mylohyoid
Function:
- Somatosensations
- Proprioceptive reflexes
- Mastication (chewing)
Signs of damage:
- Loss of facial sensations and corneal reflex on stimulation ipsilaterally
- Insignificant
- Deviation of opened jaw to ipsilateral side
CN7 Facial nerve
Facial nerve arises at junction between pons and medulla, cerebellopontine angle
6 major branches:
- Temporal branch
- Zygomatic branch
- Buccal branch (=/ Buccal nerve (V3))
- Marginal Mandibular branch
- Cervical branch
- Posterior auricular nerve
2 divisions:
- Motor root
- Intermediate nerve (smaller)
Cells of origin:
- Facial nucleus (Branchial motor) —> Facial expression
- Superior salivatory nucleus (Visceral motor) —> Nasal, Lacrimal, Salivary secretions
- Geniculate ganglion (Special sensory) —> Taste
- Geniculate ganglion (General sensory) —> Somatosensation
Central connections:
- NA
- NA
- Solitary nucleus (rostral part)
- Spinal trigeminal nucleus (caudal part)
Peripheral distribution:
- Facial muscles, buccinator, stapedius, stylohyoid, posterior belly of digastric, platysma, occipitalis
- Greater petrosal nerve —> Nerve of pterygoid canal —> **Pterygopalatine ganglion —> postganglionic via Zygomaticotemporal nerve (CNV2) —> **Lacrimal gland + ***Mucosal glands of nasal cavity and palate
- Chorda tympani —> Lingual nerve (CNV3) —> **Submandibular ganglion —> postganglionic to **Submandibular + ***Sublingual glands (記: CLS)
- Taste buds in anterior 2/3 of tongue
- Posterior auricular region, external auditory meatus, tympanic membrane
Function:
- Facial expression, articulation, winking, ingestion
- Nasal and lacrimal secretions
- Salivary secretion
- Taste
- Somatosensations
Signs of damage:
- Paralysis of ipsilateral upper and lower facial muscle
- Loss of lacrimation (tears)
- Decreased salivation; dry mouth
- Loss of taste in anterior 2/3 of tongue ipsilaterally
- Insignificant
Summary of 4 functional components of Facial nerve (2 motor, 2 sensory)
- Facial nucleus:
- convey motor impulse to muscles of face (facial expression)
- upper facial muscle: controlled bilaterally from both sides of brain
- lower facial muscle: controlled contralaterally (left brain control right face) - Superior salivatory nucleus:
- convey parasympathetic impulse to lacrimal, nasal, submandibular and sublingual salivary glands - Geniculate ganglion:
- convey sensory impulse from taste buds of anterior 2/3 of tongue - Pontine trigeminal nucleus:
- convey general sensory impulse from posterior auricular region
CN8 Vestibulocochlear nerve
2 fibres:
1. Cochlear (hearing) fibres
2. Vestibular (balance) fibres
—> both leave lateral side between pons and medulla
Cells of origin:
- Vestibular ganglion (Special sensory) —> Balance
- Spiral ganglion (Special sensory) —> Hearing
Central connections:
- Vestibular nuclei (4) + Cerebellum
- Cochlear nucleus (Dorsal + Ventral)
Peripheral distribution:
- Hair cells of ampullary crests in semicircular ducts, maculae of saccule and utricle
- Hair cells of spiral organ of Corti
Function:
- Balance
- Hearing
Signs of damage:
- Vertigo, dysequilibrium, nystagmus (involuntary eye movement)
- Neural deafness
Sense of body position in space
- Provided by information from:
1. Visual system
2. Conscious proprioceptive system
3. Vestibular system
—> lack of good vision (e.g. closure of eyes) will lead to heavy fall if vestibular system is not functioning normally
CN9 Glossopharyngeal nerve
Emerges from upper medial part of medulla
Cells of origin (5 functional components):
- Nucleus ambiguus (rostral part) (Branchial motor) —> Elevates pharynx
- Inferior salivatory nucleus (Visceral motor) —> Salivary secretion
- Inferior (petrosal) ganglion (Special sensory) —> Taste
- Inferior and superior ganglion (General sensory) —> Somatosensation
- Inferior ganglion (Visceral sensory) —> Reflex
Central connections:
- NA
- NA
- Solitary nucleus (rostral part)
- Spinal trigeminal nucleus
- Solitary nucleus
Peripheral distribution:
- Stylopharyngeus + Superior pharyngeal constrictor
- Tympanic plexus —> Lesser petrosal nerve —> **Otic ganglion —> Auriculotemporal nerve (CNV3) —> **Parotid gland (記: LOA)
- Taste buds in posterior 1/3 tongue
- Anterior surface of epiglottis, root of tongue, border of soft palate, uvula, tonsil, pharynx, auditory tube, middle ear
- Carotid sinus and bulb
Function:
- Elevates pharynx
- Salivary secretion
- Taste
- Somatosensation of tonsillar region
- Reflexes
Signs of damage:
- Slight dysphagia
- Dry mouth
- Loss of taste in posterior third of tongue ipsilaterally
- Anaesthesia of tonsillar region + loss of gag reflex from ipsilateral stimulus
- Insignificant
Summary of Glossopharyngeal nerve
Mixed nerve with motor and sensory function
Motor:
- Innervates part of tongue and pharynx —> elevates pharynx during swallowing
- Provide motor fibres to ***Parotid salivary gland
Sensory:
1. Conduct taste (posterior 1/3 tongue) and general sensory impulse from tongue and pharynx
CN10 Vagus nerve
- Only cranial nerve extend beyond head and neck
- Mixed nerve
- Most motor fibres are parasympathetic fibres to heart, lungs and visceral organs
- Supplies muscles for swallowing and vocalisation
Cells of origin (4 functional components):
- Nucleus ambiguus (Branchial motor) —> Deglutition (swallowing) + Phonation
- Dorsal motor nucleus of vagus + region of Nucleus ambiguus (Visceral motor) —> Cardiac depressor, Bronchoconstrictor, GI tract peristalsis + secretion
- Inferior (nodose) ganglion (Visceral sensory) —> Taste in epiglottis
- Inferior (nodose) ganglion (Visceral sensory) —> Visceral sensation + Reflexes
- Inferior (nodose) ganglion (Visceral sensory) —> Reflexes
- Superior (jugular) ganglion (General sensory) —> Somatosensation
Central connections:
- NA
- NA
- Solitary nucleus
- Solitary nucleus
- Solitary nucleus
- Spinal trigeminal nucleus (caudal part)
Peripheral distribution:
- Palate, pharyngeal constrictors, intrinsic muscles of larynx, ***Palatoglossus
- Cardiac nerves and plexus to heart; Pulmonary plexuses to ganglia of respiratory tree; Esophageal, Gastric, Celiac, Superior + Inferior mesenteric plexuses to myenteric and submucosal ganglia of digestive tract down to transverse colon
- Taste buds in regions of epiglottis
- Posterior epiglottis, pharynx, larynx, trachea, bronchi, esophagus, stomach, small intestine, ascending and transverse colon
- Aortic sinus and bulb
- External ear and meatus
Function:
- Deglutition (swallowing) + ***Phonation
- Cardiac depressor, Bronchoconstrictor, GI tract peristalsis + secretion
- Taste in epiglottis
- Visceral sensation + Reflexes
- Reflexes
- Somatosensation
Signs of damage:
- Dysphagia, hoarseness, paralysis of soft palate (with deviation of velum and uvula to contralateral side)
- Insignificant
- Insignificant
- Anaesthesia of ipsilateral pharynx and larynx
- NA
- Anaesthesia of ipsilateral external auditory meatus
CN11 (Spinal) Accessory nerve
2 parts:
- Cranial part (emerging from medulla)
- Spinal part (arising from superior region of spinal cord, passes upward into cranium via foramen magnum)
Cells of origin:
- Nucleus ambiguus (caudal part) (Branchial motor)
- Motoneurons of spinal accessory nucleus in C1-6 (Branchial motor)
Central connections:
NA (∵ nucleus already in CNS)
Peripheral distribution:
- Communicates with vagal branches to ***muscles of pharynx and larynx
- Sternocleidomastoid + Trapezius muscle
Function:
- Swallowing + Vocalisation
- Movements of head and shoulder
Signs of damage:
- Insignificant
- Weakness in turning head toward opposite sides and shrugging shoulder
CN12 Hypoglossal nerve
- Fibres arise from medulla (between pyramid and olive)
- Exit skull via Hypoglossal canal
- Innervates both extrinsic and intrinsic muscles of tongue —> contributes to swallowing and speech
- Supplies muscles for tongue movement
Cells of origin:
- Hypoglossal nucleus (Somatic motor)
Central connections:
NA (∵ nucleus already in CNS)
Peripheral distribution:
- Styloglossus, Hyoglossus, Genioglossus, intrinsic muscles of tongue
Function:
- Movement of tongue
Signs of damage:
- Wasting of ipsilateral tongue muscles and deviation to ipsilateral side on protrusion
(Only Genioglossus is controlled by contralateral upper motor neuron, rest of them controlled bilaterally)
(Genioglossus: contract to protrude tongue to contralateral side)
Summary: Functional components and locations of nuclei
Sensory (上—>下; 外—>內):
- Mesencephalic trigeminal
- Pontine (Principal) trigeminal
- Spinal trigeminal
- Cochlear
- Vestibular
- Solitary
Motor (外—>內; 上—>下): Midbrain region: 1. Edinger-Westphal 2. Oculomotor 3. Trochlear
Pons region:
- Trigeminal motor
- Facial
- Superior salivatory
- Abducens
- Inferior salivatory
Medulla region:
- Ambiguus
- Dorsal motor vagal
- Hypoglossal
General sensory
- CN5:
- Ophthalmic (V1), Maxillary (V2), Mandibular (V3) divisions to mucous membranes and skin of face and head
—> Trigeminal ganglion
—> Spinal trigeminal nucleus (caudal part) + Pontine trigeminal nucleus
- Muscles of mastication, peridontal membrane, temporomandibular joint, external ocular muscle
—> Mesencephalic trigeminal nucleus
- CN7:
- Posterior auricular region, external auditory meatus, tympanic membrane
—> ***Geniculate ganglion
—> Spinal trigeminal nucleus (caudal part) - CN9:
- Tonsillar region (Anterior surface of epiglottis, root of tongue, border of soft palate, uvula, tonsil, pharynx, auditory tube, middle ear)
—> **Inferior and **Superior ganglion
—> Spinal trigeminal nucleus - CN10:
- External ear and meatus
—> ***Superior (jugular) ganglion
—> Spinal trigeminal nucleus (caudal part)
Visceral sensory
- CN9
- Carotid sinus and bulb —> ***Inferior ganglion —> Solitary nucleus - CN10
- Taste in epiglottis / Visceral sensation + Reflexes (Posterior epiglottis, pharynx, larynx, trachea, bronchi, esophagus, stomach, small intestine, ascending and transverse colon) / Reflexes (Aortic sinus and bulb)
—> ***Inferior (nodose) ganglion
—> Solitary nucleus
Special sensory
- CN1
- Smell —> Bipolar cells in olfactory epithelium —> Olfactory bulb - CN2
- Vision —> Retinal ganglion cells —> Lateral geniculate nuclei - CN7 (anterior 2/3 tongue)
- Taste —> Geniculate ganglion —> Gustatory / Solitary nucleus (rostral part) - CN8
- Balance —> Vestibular ganglion —> Vestibular nuclei + Cerebellum
- Sound —> Spiral ganglion —> Dorsal + Ventral Cochlear nucleus - CN9 (posterior 1/3 tongue)
- Taste —> Inferior (petrosal) ganglion —> Gustatory / Solitary nucleus (rostral part)
Somatic motor
- CN3
- Oculomotor nucleus —> Superior, Inferior, Medial rectus muscle; Inferior oblique; Levator palpebrae superioris (Ipsilateral) - CN4
- Trochlear nucleus —> Superior oblique muscle (***Contralateral) - CN6
- Abducens nucleus —> Lateral rectus muscle (Ipsilateral) - CN12
- Hypoglossal nucleus —> Styloglossus, Hyoglossus, Genioglossus, intrinsic muscles of tongue (Palatoglossus by CN10) (Ipsilateral)
***Branchial motor
- CN5
- Trigeminal motor nucleus
—> Temporalis, Masseter, Lateral and Medial pterygoids + Tensor veli palatini and Tensor tympani, Anterior belly of digastric, Mylohyoid - CN7
- Facial nucleus
—> Facial muscles, Buccinator, Stapedius, Stylohyoid, Posterior belly of digastric, Platysma, Occipitalis - CN9
- Nucleus ambiguus (rostral part)
—> ***Stylopharyngeus + Superior pharyngeal constrictor - CN10
- Nucleus ambiguus
—> Palate, Pharyngeal constrictors, Intrinsic muscles of larynx, ***Palatoglossus
—> Swallowing + Phonation - CN11
- Nucleus ambiguus (caudal part)
—> Sternocleidomastoid + Trapezius muscle / Communicates with vagal branches to ***muscles of pharynx and larynx
Visceral motor (parasympathetic)
- CN3
- Edinger-Westphal nucleus
—> **Ciliary ganglion: postganglionic via short ciliary nerves to **sphincter of pupil + ***Ciliary muscle - CN7
- Superior salivatory nucleus - Greater petrosal nerve —> Nerve of pterygoid canal —> **Pterygopalatine ganglion —> postganglionic via Zygomaticotemporal nerve (CNV2)—> **Lacrimal gland + ***Mucosal glands of nasal cavity and palate
—> Nasal and lacrimal secretions -
**Chorda tympani —> **Lingual nerve (CNV3) —> **Submandibular ganglion —> postganglionic —> **Submandibular + ***Sublingual glands (記: CLS)
—> Salivary secretion - CN9
- Inferior salivatory nucleus
—> Tympanic plexus —> **Lesser petrosal nerve —> **Otic ganglion —> **Auriculotemporal nerve (CNV3) —> **Parotid gland (記: LOA)
—> Salivary secretion - CN10
- Dorsal vagal nucleus
- Nucleus ambiguus
—> Cardiac depressor, Bronchoconstrictor, GI tract peristalsis + secretion
CNV1 branches
- Nasociliary nerve
- Sensory root of ciliary ganglion
- Posterior ethmoidal nerve
- Long ciliary nerve
- **Infratrochlear nerve
- Anterior ethmoidal nerve —> **External nasal nerve - ***Lacrimal nerve
- Frontal nerve
- **Supratrochlear nerve
- **Supraorbital nerve
CNV2 branches
In the cranium
1. Middle meningeal nerve
From pterygopalatine fossa
- Zygomatic nerve (Zygomaticotemporal nerve, Zygomaticofacial nerve), through the Inferior orbital fissure
- Nasopalatine nerve
- Posterior superior alveolar nerve
- Greater palatine nerves
- Lesser palatine nerves
- Pharyngeal nerve
In the infraorbital canal
- Middle superior alveolar nerve
- Anterior superior alveolar nerve
- Infraorbital nerve
Face:
- Inferior palpebral nerve
- Superior labial nerve
- Lateral nasal nerve
CNV3 branches
Trunk branches (before the division)
- Muscular branches: motor nerves for Medial pterygoid, Tensor tympani, Tensor veli palatini
- Meningeal branch (sensory)
Anterior division
- ***Buccal nerve (sensory)
- Masseteric nerve (motor)
- Deep temporal nerves (motor)
- Lateral pterygoid nerve (motor)
Posterior division
- ***Auriculotemporal nerve (sensory)
- ***Lingual nerve (sensory)
- Inferior alveolar nerve (sensory + motor) —> Nerve to **Mylohyoid (motor, also supplies **Anterior belly of digastric) + Mental nerve
