What are the cranial nerves?
- Olfactory
- Optic
- Oculomotor
- Trochlear
- Trigeminal (VI,2,3)
- Abducens
- Facial
- Vestibulocochlear
- Glossopharyngeal
- Vagus
- Accessory
- Hypoglossal
what consistency are nerves?
soft and squishy
what are the different fibres that the nerves may contain? (x5)
- somatic motor ie striated muscle
- visceral motor ie cranial division of parasympathetic supply innervates smooth muscle and glands
- visceral sensory ie afferent inputs from pharynx, larynx, heart, lung, gut etc
- general sensory - afferent inputs (eg touch, temperature, pain) from skin & mucous membranes
- special sensory – taste, smell, vision, hearing & balance
Is each nerve sensory/motor/ or both?
- Olfactory (CNI) –sensory (smell)
- Optic (CNII) –sensory (vision)
- Oculomotor (CNIII) –motor (eye movement)
- Trochlear (CNIV) –motor (eye movement)
- Trigeminal (CNV) –mixed (V1&2=sensory, V3= sensorimotor)
- Abducent (CNVI) –motor (eye movement)
- Facial (CNVII)–mixed
- Vestibulocochlear (CNVIII) –sensory (hearing & balance)
- Glossopharyngeal (CNIX) –mixed
- Vagus (CNX) –mixed
- Accessory (CNXI) –motor
- Hypoglossal (CNXII) -motor (tongue)
Olfactory nerve:
- pathway
- components
- clinical application
- pathway
- receptors in olfactory epithelium of nasal cavity,
olfactory nerve fibres pass through foramina
in cribriform plate of ethmoid bone and enter
olfactory bulb in the anterior cranial fossa
- Components
special sensory –> smell
- Clinical application
Fractured cribriform plate may tear olfactory nerve fibres causing anosmia
Optic nerve:
- pathway
- components
- clinical application
- Pathway
- enters via optic canal, nerves join to form optic chiasm, fibres from medial (nasal) half of each retina cross to form optic tract
- Components
- special sensory –> vision
- Clinical application
- increase in CSF pressure can cause papilloedema
- section of right optic nerve causes blindness through right eye
- section of optic chiasm causes loss of peripheral vision (bitemporal hemianopsia)
- section of right optic tract causes blindness in left temporal & right nasal fields (left homonymous hemianopsia)
Oculomotor nerve:
- pathway
- components
- clinical application
- Pathway
- emerges from midbrain and exits via superior orbital fissure
- Components
- somatic motor –> extraocular muscles (superior, medial & inferior rectus & inferior oblique) and eyelid (levator palpebrae superioris)
- visceral motor –> parasympathetic to pupil causing constriction and to ciliary muscle causing accommodation of the lens
- Clinical application
- drooping of upper eyelid (ptosis)
- eyeball abducted and pointed down
- no pupillary reflex
- no accommodation of lens
Trochlear nerve:
- pathway
- components
- clinical application
- Pathway
emerges from dorsal surface of the mid brain and exits via the superior orbital fissure
- Components
somatic motor –extraocular muscle –> SO
- Clinical application
- diplopia when looking down
Trigeminal VI (opthalmic) nerve:
- pathway
- components
- clinical application
- Pathway
Emerges from the pons, travels through trigeminal ganglion & exits via superior orbital fissure
- Components
General sensory- from cornea, forehead, scalp, eyelids, nose and mucosa of nasal cavity & sinuses
Trigeminal V2 (maxillary) nerve:
- pathway
- components
- clinical application
- Pathway
Emerges from the pons, travels through the trigeminal ganglion & exits via the foramen rotundum
- Components
General sensory – from face over maxilla, maxillary teeth, TM joint, mucosa of nose, maxillary sinuses and palate
Trigeminal V3 (mandibular) nerve:
- pathway
- components
- clinical application
- Pathway
- emerges from the pons, travels through the trigeminal ganglion & exits via foramen ovale
- Components
- general sensory –> from the face over mandible, mandibular teeth, TM joint, mucosa of mouth & anterior 2/3 of tongue
- somatic motor–> muscles of mastication, part of digastric, tensor veli palatini & tensor tympani
- Clinical application
- paralysis of muscles of mastication
- loss of corneal or sneezing reflex
- trigeminal neuralgia
- loss of sensation in the face
Abducens nerve:
- pathway
- components
- clinical application
- Pathway
- emerges between pons & medulla & exits via superior orbital fissure
- Components
- somatic motor –> lateral rectus muscle (abducts eye)
- Clinical application
- medial deviation of the affected eye causing diplopia
Facial nerve:
- pathway
- components
- clinical application
- Pathway
- emerges between pons & medulla & exits via internal acoustic meatus, facial canal & stylomastoid foramen
- Components
somatic motor – muscles of facial expression & scalp, stapedius of middle ear, part of digastric muscle
visceral motor- parasympathetic innervation of submandibular & sublingual salivary glands, lacrimal glands, glands of nose & palate
special sensory- taste from anterior 2/3 of tongue & soft palate
general sensory- from external acoustic meatus
- Clinical application
- most frequently injured – due to long pathway through bone
- Bell’s palsy- cannot frown, close eyelid, or bare teeth
Vestibulocochlear nerve:
- pathway
- components
- clinical application
- Pathway
- emerges from between pons & medulla and exits via
internal acoustic meatus, dividing into vestibular
and cochlear nerves
- Components
- special sensory –> vestibular sensation from semi-circular ducts, utricle, saccule, gives sense of position & movement
- hearing from spiral organ
- Clinical application
- tinnitus (ringing of ears)
- deafness (conductive vs sensorineural)
- vertigo (loss of balance)
- nystagmus (involuntary rapid eye movements)
Glossopharyngeal (rememer tongue and pharynx) nerve:
- pathway
- components
- clinical application
- pathway
- emerges from medulla & exits via jugular foramen
- components
- special sensory–> taste from posterior 3rd of tongue
- general sensory –> sensation from middle ear & posterior oral cavity
- visceral sensory –> sensation from carotid body & carotid sinus
- visceral motor –> parasympathetic innervation of parotid gland
- somatic motor –> to stylopharyngeus, helps with swallowing
- clinical application
- loss of gag reflex and taste from back of tongue
- associated with injuries to CNs X & XI – jugular foramen syndrome
Vagus nerve:
- pathway
- components
- clinical application
- Pathway
Emerges from medulla and exits via jugular foramen, then goes everywhere
- Components
- special sensory –> taste from epiglottis and
palate
-general sensory –> sensation from auricle,
external acoustic meatus
-visceral sensory –> from pharynx, larynx, trachea,
bronchi, heart, oesophagus, stomach, intestine
-visceral motor –> parasympathetic innervation
to muscle in bronchi, gut and heart
-somatic motor –> to pharynx, larynx, palate and
oesophagus
- Clinical application
- damage to pharyngeal branches causes difficulty swallowing
- damage to laryngeal branches causes difficulty in speaking
Accessory nerve:
- pathway
- components
- clinical application
- pathway
- small cranial (medulla) & large spinal roots exit via
jugular foramen
- components
- somatic motor –> striated muscle of soft palate, pharynx, larynx, sternocleidomastoid & trapezius
- clinical application
- weakness in turning head & shrugging shoulder
Hypoglossal nerve:
- pathway
- components
- clinical application
- pathway
- emerges from the medulla and exits through the
hypoglossal canal
- components
- somatic motor –> to muscles of tongue
- clinical application
- vulnerable to damage during tonsillectomy
- causes paralysis & atrophy of ipsilateral half of
tongue. Tip deviates towards affected side.
