cranial nerves Flashcards
what do cranial nerves may contain
Somatic motor fibres - supply striated muscle
(don’t worry about the somatic vs branchial distinction)
Autonomic motor fibres - cranial division of the parasympathetic supply innervates smooth muscle & glands
Visceral sensory - afferent inputs from pharynx, larynx, heart, lung, gut etc - not normally conscious
General sensory - afferent inputs (eg touch, temperature, pain) from skin & mucous membranes
Special sensory – taste, smell, vision, hearing & balance
function of olfactory
sensory (smell)
function of optic
sensory (vision)
function of oculomotor
motor (eye movement)
function of trochlear
motor (eye movement)
function of trigeminal
mixed (sensation from face & mouth, muscles of mastication)
function of abducent?
motor (eye movement)
function of facial nerve
mixed (muscles of facial expression, parasymp, taste)
function of vestibulocochlear
sensory (hearing & balance)
function of glossopharyngeal
mixed ( swallowing, sensation from tongue, parasymp)
function of vagus nerve
mixed (muscles of throat, parasymp, visceral sensory)
function of accessory nerve
motor (soft palate, throat & neck)
function of hypoglossal nerve
motor (tongue)
whats the pathway of the olfactory nerve
receptors in olfactory epithelium of nasal cavity, olfactory nerve fibres pass through foraminifera in cribriform plate of ethmoid bone and enter olfactory bulb in the anterior cranial fossa
what are the components of olfactory nerve
special sensory - smell
what is the clinical application of the olfactory nerve
fractured cribriform plate may tear olfactory nerve fibres causing anosmia
what is the pathway of the optic nerve
enters via optic canal, nerves join to form optic chiasm, fibres from medial (nasal) half of each retina cross to form optic tract
what are the components of the optic nerve
special sensory - vision
clinical application of the optic nerve
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 and right nasal fields (left homonymous hemianopsia)
pathway of the oculomotor nerve
emerges from midbrain and exits via superior orbital fissure
what are the components of the oculomotor nerve?
somatic motor - extraocular muscles (superior, medial & inferior rectus and inferior oblique) and eyelid (levator palpebrae superioris)
autonomic motor - parasympathetic to pupil causing constriction and to ciliary muscle causing accommodation of the lens
what is the clinical application of the oculomotor nerve?
drooping of upper eyelid (ptosis)
eyeball abducted and pointing down
no pupillary reflex
no accommodation of the lens
what is the pathway of the trochlear nerve
emerges from dorsal surface of the mid brain and exits via the superior orbital fissure
what are the components of the trochlear
somatic motor - extraocular muscle (superior oblique turns eye downwards)
what is the clinical application of the trochlear nerve
diplopia when looking down
what is the pathway of the abducenet nerve
emerges between pons and medulla and exits exits via the superior orbital fissure
what is the compinent of the abducent nerve
somatic motor - extraocular muscle (lateral rectus abducts the eye)
what is the clinical application of the abducent nerve?
medial deviation of the affected eye causing diplopia
what is the pathway of the trigeminal V1 nerve
emerges from the pons, travels through the trigeminal ganglion and exits via the superior orbital fissure
what are the components of the trigemnial V1
General sensory - from cornea, forehead, scalp, eyelids, nose and mucosa of nasal cavity and sinuses
what is the pathway of the trigeminal V2 nerve
emerges from the pons, travels through the trigeminal ganglion and exits via the foramen rotundum
what is the component of the trigeminal V2 nerve
General sensory - from face over maxilla, maxillary teeth, temperomandibular joint, mucosa of nose, maxillary sinuses and palate
what is the pathway of trigeminal V3 nerve
emerges from the pons, travels through the trigeminal ganglion and exits via the foramen ovale
what is the components of the trigeminal V3 nerve
General sensory - from face over mandible, mandibular teeth, temperomandibular joint, mucosa of mouth & anterior 2/3rds of tongue
Somatic motor - muscles of mastication, part of digastric, tensor veli palatini & tensor tympani
what is the clinical application of the trigeminal V3 nerve
paralysis of muscles of mastication
loss of corneal or sneezing reflex
loss of sensation in the face
trigeminal neuralgia
what is the pathway of the facial nerve
emerges between pons and medulla and exits via internal acoustic meatus, facial canal and stylomastoid foramen
what is the components of the facial nerve?
somatic motor - muscles of facial expression & scalp, stapedius of middle ear, part of digastric muscle
autonomic motor - parasympathetic innervation of submandibular & sublingual salivary glands, lacrimal glands, glands of nose & palate
special sensory - taste from anterior 2/3rd of tongue & soft palate
general sensory - from external acoustic meatus
what is the clinical application of the facial nerve
most frequently injured - due to long pathway through bone
Bell’s palsy - cannot frown, close eyelid, or bare teeth
what is the pathway of the vestibulocochlear
emerges from between pons and medulla and exits via internal acoustic meatus, dividing into vestibular & cochlear nerves
what is the components of the vestibulocochlear nerve
special sensory - vestibular sensation from semicircular ducts, utricle,
saccule gives sense of position & movement
hearing from spiral organ
what is the clinical application of the vestibulocochlear nerve
tinnitus (ringing in the ears)
deafness (conductive vs sensorineural)
vertigo (loss of balance)
nystagmus (involuntary rapid eye movements)
what is the pathway of the glossopharyngeal nerve
emerges from medulla and exits via jugular foramen
what are the components of the glossopharyngeal nerve?
special sensory - taste from posterior 3rd of tongue
general sensory - cutaneous sensations from middle ear and posterior oral cavity
visceral sensory - sensation from carotid body & carotid sinus
autonomic motor - parasympathetic innervation of parotid gland
somatic motor - to stylopharyngeus, helps with swallowing
what is the clinical applicaation of the glosspharyngeal nerve
loss of gag reflex and taste from back of tongue
associated with injuries to CNs X and XI - jugular foramen syndrome
what is the pathway of the vagus nerve
emerges from medulla and exits via jugular foramen, then everywhere
what are the components of the vagus nerve
special sensory - taste from epiglottis and palate
general sensory - sensation from auricle, external acoustic meatus
visceral sensory - from pharnyx, larynx, trachea, bronchi, heart, oesophagus, stomach, intestine
autonomic motor - parasympathetic innervation of muscle in bronchi, gut, heart
somatic motor - to pharynx, larynx, palate & oesophagus
what are the clinical application of the vagus nerve
damage to pharyngeal branches cause difficulty in swallowing
damage to laryngeal branches causes difficulty in speaking
what is the pathway of the accessory nerve?
small cranial (medulla)* and large spinal roots exit via jugular foramen
what are the components of the accessory nerve
somatic motor - striated muscle of soft palate, pharynx & larynx, and to sternocleidomastoid & trapezius
what is the clinical application of the accessory nerve?
weakness in turning head and shrugging shoulder
what is the pathway for hypoglossal nerve?
emerges from medulla and exits through the hypoglossal canal
what are the components of the hypoglossal nerve?
somatic motor - to muscles of tongue
what are the clinical application of the hypoglossal nerve
vulnerable to damage during tonsillectomy
causes paralysis & atrophy of ipsilateral half of tongue. Tip deviates towards affected side
overview of the nerves
Smell - Olfactory
Sight - Optic
Taste - Facial, Glossopharyngeal & Vagus
Hearing & Balance - Vestibulocochlear
Movement of the eyes - Oculomotor, Trochlear & Abducent
Accomodation of the eye – Oculomotor
Constriction of the pupil - Oculomotor
Movement of muscles in the face - Facial
Sensation from the face - Trigeminal
Chewing - Trigeminal (mandibular)
Swallowing - Glossopharyngeal & Accessory
Movement of the tongue - Hypoglossal
Movement of the vocal cords – Vagus
Movement of the neck - Accessory