Cranial nerves - physiology Flashcards
List the 5 fibre types that cranial nerves carry
Somatic motor
Parasympathetic (visceral/autonomic motor)
Visceral sensory (NOT AUTONOMIC)
General sensory
Special sensory
What fibre type do cranial nerves not carry
Sympathetic
What do somatic motor fibres in cranial nerves innervate
Skeletal muscle
What do parasympathetic (visceral (autonomic) motor fibres) in cranial nerves innervate
Smooth muscle and glands
What function do special sensory fibres carry (5)
Taste Smell Vision Hearing Balance
Where are the cell bodies of sensory fibres located
Outside spinal cord in ganglia - DRG
Where are the cell bodies of somatic motor fibres located
Ventral horn of spinal cord
Where are the cell bodies of autonomic motor fibres located (2)
One in the ventral horn and one outside the spinal cord at the autonomic ganglia
What fibre type does CN I carry
Special sensory
Function of CN I
Smell
Pathway of CN I
Receptors in olfactory epithelium of nasal cavity innervated by olfactory nerve fibres pass through foramen in cribriform plate of ethmoid bone and enter olfactory bulb in the anterior cranial fossa
Fractured cribriform plate may result in what
Tear olfactory nerves and cause anosmia (loss of smell)
What fibre type does CN II carry
Special sensory
Function of CN II
Vision
A lesion in the optic chiasm causes loss of central or peripheral vision
peripheral (bitemporal hemianopia)
What fibre types does CN III carry (2)
Somatic motor
Parasympathetic (visceral motor)
Functions of CN III (3)
Somatic motor
-innervate extra ocular muscles (except SO & LR) + LPS
Parasympathetic (visceral motor)
- innervates sphincter pupillae –> constrict pupils
- innervates ciliaris –> accomodation of lens
Damage to CN III can result in what (4)
Drooping of eyelids - as LPS not working
Eye abducted and pointing down
No pupillary reflex
No accommodation of lens
What fibre type does CN IV carry
Somatic motor
Function of CN IV
Innervates SO so intorts (inwards and downwards) the eye
Where does CN IV emerge from and exit
Emerges from dorsal surface of midbrain and exits via the superior orbital fissure
Resulting effect when CN IV is damaged
Diplopia
Where does CN VI emerge from and exit
Emerges from pontomedullary junction and exits via superior orbital fissure
What fibre type does CN VI carry
Somatic motor
Function of CN VI
Innervates LR to abduct the eye
Resulting effect when CN VI is damaged
Medial deviation –> diplopia
Where does CN V1 emerge from and exit
emerges from the pons, travels through the trigeminal ganglion and exits via the superior orbital fissure
What fibre type does CN V1 carry
General sensory - from top 1/3 of face (cornea, forehead, scalp, eyelids, nose etc)
Where does CN V2 emerge from and exit
emerges from the pons, travels through the trigeminal ganglion and exits via the foramen rotundum
What fibre type does CN V2 carry
General sensory - from maxilla area, maxillary teeth, TMJ, mucosa of nose)
Where does CN V3 emerge and exit
emerges from the pons, travels through the trigeminal ganglion and exits via the foramen ovale
What fibre types does CN V3 carry (2)
General sensory - from mandibular area, anterior 2/3 tongue
Somatic motor - to muscles of mastication, tensor veli palatini…
Resulting effects when CN V3 is damaged (4)
paralysis of muscles of mastication
loss of corneal or sneezing reflex
loss of sensation in the face + anterior 2/3 tongue
trigeminal neuralgia – quite severe
Where does CN VII emerge and exit
emerges between pons and medulla and exits via internal acoustic meatus –> passes into the facial canal (in the petrous temporal bone of ear) –> extends inferiorly and laterally to exit at stylomastoid foramen
What fibre types does CN VII carry (4)
Somatic motor
Parasympathetic (visceral motor)
Special sensory
General sensory
Functions of CN VII (4)
-Somatic motor
- Parasympathetic (visceral motor)
- Special sensory
- General sensory
Innervates muscles of facial expression, scalp, stapedius
Innervates submandibular/sublingual salivary glands, lacrimal gland
Taste sensation to anterior 2/3 tongue (chorda tympani)
General sensation from external acoustic meatus
Resulting effects when CN VII is damaged (4)
Can’t close eyes/ bare teeth/ smile/ wrinkle forehead/ puff cheeks
Lose taste in anterior 2/3 tongue
Lose general sensation from external acoustic meatus
Lose saliva production from submandibular/sublingual glands & tear production from lacrimal gland
What condition is associated with CN VII palsy
Bell’s palsy
Where does CN VIII emerge and exit
emerges frompontomedullary junction and exits via internal acoustic meatus, dividing into vestibular & cochlear nerves
What fibre type does CN VIII carry (1)
Special sensory
Functions of CN VIII (2)
-special sensory
Provides vestibular sensation from semicircular canals, utricle and saccule - giving sense of position + movement
Provides hearing from cochlea
Resulting effects when CN VIII is damaged (4)
tinnitus (ringing in the ears/abnormal sounds with no external source)
deafness (conductive vs sensorineural)
vertigo (loss of balance)
nystagmus (involuntary rapid eye movements)
Where does CN IX
emerges from medulla and exits via jugular foramen
What fibre types does CN IX carry (5)
Special sensory General sensory Visceral sensory Parasympathetic (visceral motor) Somatic motor
Functions of CN IX (5)
- Special sensory
- General sensory
- Visceral sensory
- Parasympathetic (visceral motor)
- Somatic motor
taste from posterior 1/3 of tongue
cutaneous sensations from middle ear and posterior oral cavity
sensation from carotid body & carotid sinus
parasympathetic innervation of parotid gland
to stylopharyngeus, helps with swallowing
List some resulting effects when CN IX is damaged
loss of gag reflex and taste from back of tongue
Where does CN X emerge and exit
emerges from medulla and exits via jugular foramen
What fibre types does CN X carry (5)
Special sensory General sensory Visceral sensory Parasympathetic (visceral motor) Somatic motor
Functions of CN X
- Special sensory
- General sensory
- Visceral sensory
- Parasympathetic (visceral motor)
- Somatic motor
Taste from epiglottis and palate
Sensation from auricle, external acoustic meatus
sensation from resp tract, GI tract, heart
Motor to muscle in bronchi, GI tract, heart
Motor to pharynx, larynx, palate, oesophagus
Damage to pharyngeal branches of CN X cause difficulty in what
swallowing
Damage to laryngeal branches of CN X causes difficulty in what
Speaking –> hoarse voice
Where does CN XI emerge and exit
Small cranial (medulla) and large spinal roots exit via jugular foramen
What fibre type does CN XI carry
Somatic motor
Function of CN XI
-somatic motor
motor to striated muscle of soft palate, pharynx & larynx, and to sternocleidomastoid & trapezius
Resulting effect when CN XI is damaged
Weakness in turning head and shrugging shoulder
Where does CN XII emerge and exit
emerges from medulla and exits through the hypoglossal canal
What fibre type does CN XII carry
Somatic motor
Function of CN XII
motor to all muscles of tongue EXCEPT PALATOGLOSSUS (CN X)
Resulting effect when CN XII is damaged
vulnerable to damage during tonsillectomy
-causes paralysis & atrophy of ipsilateral half of tongue
