Week 3 Lecture 7: Cranial nerves Flashcards
Which cranial nerves emerge from the brainstem?
- 3-12 so they are therefore part of our CNS.
- CN I and II are not true peripheral cranial nerves - they are part of the CNS
For each fibre type within a cranial nerve, there is a corresponding ______ in the brain stem
nucleus
Which two fibres (and therefore two nuclei) form the oculomotor nerve?
- Oculomotor nucleus: somatic motor fibres to extraocular muscles
- Edinger-westphal nucleus - visceral motor (autonomic) fibres to provide parasympathetic information to the sphincter pupillae and ciliary muscles
Cranial nerve nuclei are scattered throughout brainstem. Where are sensory and motor nuclei located?
Located within the tegmentum of the brainstem:
sensory nuclei - located lateral
motor nuclei - located medial
Explain what type of fibre types travel to:
- skin of face
- tongue
- eye muscles
- neck muscles
- salivary glands
- organs
- sensory
- taste sense
- motor
- motor
- visceral motor
- visceral sensory
What is visceral motor information?
- autonomic division of CNS
- represents motor innervation of smooth muscle, cardiac muscle and gland cells
What is a nucleus?
a functional group of neurones within the CNS
Which cranial nerves are found in:
- the midbrain
- the pons
- the medulla
- CN III and IV
- CN V, VI, VII, VIII
- CN IX, X, XI, XII
How many cranial nerves are:
- purely motor
- purely sensory
- mixed
- 5
- 3
- mixed
How do sensory nerve nuclei work?
receive information from fibres entering brainstem in cranial nerves which synapse here, and nuclei then send fibres to appropriate higher centre
How do motor nerve nuclei work?
receive motor information from higher centre which synapse and give rise to motor fibres that leave the brainstem in cranial nerves
Where is cranial nerve 1 and 2 derived from?
forebrain (not the brainstem)
Where is CN I (Olfactory nerve) located?
from the nasal mucosa, CN I merges with olfactory tracts and bulbs which are extensions of the telencephalon
What foramina does CN I use to exit the brainstem?
cribriform plate of ethmoid bone
What is the function of CN I and how do we test its function?
Function: special sensory - smell
Test: offer a familiar smelling item e.g orange
What is anosmia?
inability to smell
Where is CN II (optic nerves) located?
- emerge from retina
- travel through optic canal to cranial cavity, to optic chiasma
- optic tracts then carry visual information to the thalamus
- thalamus relay the information to the primary visual cortex
Which structure do all our sensory modalities go through? (except smell)
thalamus
Which foramina does CN II use to exit the brainstem?
optic canals
What is the function of CN II and how do we test its function?
function - vision test - various visual tests e.g fundoscopy
Where is CN III (oculomotor) found?
pontomesencephalic junction then emerges anteriorly in between the cerebral peduncles
Which foramina does CN III use to exit the brainstem?
Superior orbital fissure
What are the functions of CN III?
- somatic motor to four extra ocular muscles
- visceral (parasympathetic) motor to ciliary muscle and sphincter pupillae
What is CN IV and where is it located?
trochlear nerve
location: dorsal midbrain
What is the function of CN IV?
Somatic motor to superior oblique
Which foramina does CN IV use to exit the brainstem?
superior orbital fissure
Which is cranial nerve VI, where is it located and which foramen does it travel through?
- abducens
- located in pontomedullary junction
- exits the brainstem via the superior orbital fossa (same as CN III, CN IV)
What is the function of cranial nerve VI?
Somatic motor supply to lateral rectus
How do we test the function of CN III, IV and VI?
follow finger (H) test
What is the pneumonic to remember the innervation of the extraocular muscles
LR6SO4AO3
Lateral rectus - CN VI
Superior oblique - CN IV
All others - CN III
Which muscles are responsible for moving the eyelid up and to the right/left?
inferior oblique and superior rectus
What muscles are responsible for moving the eyelids left and right
lateral and medial rectus
What muscles are responsible for moving the eyelids down and to the right?
superior oblique and inferior rectus
Which muscle is responsible for closing of the eyelid?
orbicularis oculi
Which muscles are responsible for opening the eyelid?
- Levator palpebrae superioris opens the eyelid
- superior tarsal muscle keeps it open
Which muscle:
- dilates pupil
- constricts pupil
- changes shape of lens
- dilators of iris
- sphincter pupillae
- ciliary muscle
What are the 3 branches of the trigeminal nerve and where are they located?
V1- Ophthalmic division
V2 - Maxillary division
V3 - Mandibular division
location - pons
Which foramina does each branch of CN V use to exit the brainstem?
v1 - enters superior orbital fissure to make its way to orbit
v2- foramen rotundum
v3- foramen ovale
what is the function of the ophthalmic division of the trigeminal nerve and how do we test its function?
somatic sensation from upper face (above eye but includes the upper eyelid)
test - cotton wool bud on forehead
what is the function of the maxillary division of the trigeminal nerve and how do we test its function?
somatic sensation from middle face (between eye and mouth)
test - cotton wool bud on cheek
What are the functions of the mandibular division of the trigeminal nerve?
- somatic sensation from lower face mandible and anterior 2/3 tongue
- brachial (somatic) motor to muscles of mastication, anterior belly of digastric, tensor tympani, others
How do we test the function of the mandibular branch of the trigeminal nerve?
-cotton wool bud on jaw
-clench teeth
protrude jaw
-move side to side against resistance (testing pterygoids)
-jaw-jerk reflex
What are the 4 ganglia of the head and neck that are associated with the trigeminal nerve?
- ciliary
- pterygopalatine
- submandibular
- otic
What is a ganglia?
- function like relay stations
- one nerve enters and another exits
- contains cell bodies and glial cells supported by connective tissues
What is CN VII and where is it located?
- facial nerve
- located in the cerebellopontine angle
Which foramina does CN VII use to enter and exit the brainstem?
enters at Internal acoustic meatus
exits at the stylomastoid foramen
What are the functions of the facial nerve?
- brachial motor to muscles of facial expression, stapedius muscle, posterior belly of digastric
- taste to anterior 2/3rd of tongue
- somatic sensory to skin of ear
- visceral motor (parasympathetic) to all glands except parotid e.g lacrimal
Which branch of the facial nerve supplies the anterior 2/3rds of tongue?
chorda tympani
Which nerve helps to protect structures of ear when we hear loud music?
facial nerve
How would we test the function of CN VII?
Facial movements, taste, salivation
What is CN VIII and where is it found?
- vestibulocochlear
- location: cerebellopontine angle
Which foramina does CN VIII use to exit the brainstem?
Internal acoustic meatus (IAM)
What is the function of CN VIII?
Special sensory - hearing and balance
How can we test the function of CN VIII?
Bedside hearing tests (Rinne’s and Weber’s test)
Why are CN VII and CN VIII closely linked?
emerge closely together and use the same foramen (internal acoustic meatus)
What is CN IX and where is it located?
- glossopharyngeal
- location: posterolateral sulcus of medulla, lateral to olives
Which foramina does CN IX use to exit the brainstem?
Jugular foramen
What are the functions of CN IX?
- brachial motor for swallowing (pharynx)
- visceral motor (parasympathetic) to parotid gland
- special sensory for taste to posterior 1/3 of tongue
- somatic sensory to middle ear, pharynx, posterior 1/3rd tongue
- visceral sensation from carotid body and carotid sinus monitoring O2 and BP
What is the test for CN IX?
gag reflex
Where is CN X located?
- vagus nerve
- location: posterolateral sulcus of medulla, lateral to olives
Which foramina does CN X use to exit the brainstem?
Jugular foramen
What is the function of CN X?
- brachial motor to muscles of pharynx and larynx, muscles of soft palate (uvula)
- visceral motor (parasympathetic) to thoracic and GI tract and visceral sensory
- special sensory taste from epiglottis and palate
- somatic sensation from epiglottis, skin of external ear, larynx
How can we test the function of CN X?
Speaking, movement of uvula
What structures monitor oxygenation and blood pressure and is innervated by CN IX?
Carotid body and sinus
What is CN XI and where is it located?
- accessory
- location: caudal medulla and rostral spinal cord
Which foramina does CN XI use to exit the brainstem?
Jugular foramen
What is the function of CN XI?
Somatic motor to sternocleidomastoid and trapezius
How do we test for CN XI?
Shrug shoulder and rotate head against resistance
What is CN XII and where is it located?
- hypoglossal
- anterolateral sulcus (between pyramid and olives)
Which foramina does CN XII use to exit the brainstem?
Hypoglossal canal
What is the function of CN XII and how do we test that function
function - somatic motor to muscles of tongue test - protrude tongue
What would injury to the hypoglossal nerve cause?
deviation of the tongue toward the paralysed side
