Lecture 7 - Cranial Nerves (part 1) Flashcards
How many paired cranial nerves are there?
12
How are the cranial nerves numbered?
from rostral to caudal
What do cranial nerves carry both of?
sensory and motor information
What are the 6 modalities of cranial nerves?
sensory: somatic, special, visceral
motor: somatic, branchial, visceral
What are examples of somatic sensory modalities?
touch (pain, temperature, vibration)
What are examples of special sensory modalities?
vision, hearing, taste, smell, balance
What are examples of visceral sensory modalities?
organs (pain)
What are examples of somatic motor modalities?
skeletal muscle derived from somites
What are examples of branchial motor modalities?
skeletal muscle derived from pharyngeal arches
What are examples of visceral motor modalities?
parasympathetic only (craniosacral outflow)
How do most cranial nerves enter/exit?
through the brainstem
Which cranial nerves do not pass through brainstem
I, II, XI
What are the 12 cranial nerves?
olfactory
optic
oculomotor
trochlear
trigeminal
abducens
facial
vestibulocochlear
glossopharyngeal
vagus
spinal accessory
hypoglossal
Where are the bipolar neurons found in the olfactory nerve?
olfactory epithelium (roof of nasal cavity)
What do peripheral processes have?
cilia
What are cilia in the nose stimulated by?
odorous substances
What foramina does the olfactory nerve travel through?
the cribriform plate
Where do bipolar neurons in the olfactory epithelium synapse in?
the olfactory bulbs
After synapsing in the olfactory bulbs, where do bipolar neurons go?
in the cerebral cortex
What type of modality is the olfactory nerve?
special sensory
Where is the olfactory nerve located?
inferior aspect of frontal lobes
What is found in the upper nasal cavity?
dissolved odorants
Where does the optic nerve transmit visual information?
from retina into the skull
Which foramen does the optic nerve pass through?
the optic canal
Where is the location of the optic nerve?
exits orbit and contributes to optic chiasm anterior to pituitary gland
What is the pathway of neurons of the optic nerve?
Some neurons cross the midline at the optic chiasm -> continue
as optic tracts with information from left visual field on right (& vice versa)
synapse in thalamus (lateral geniculate nucleus) -> then carried to cortex
Where does the optic nerve synapse before carried to cortex?
in the thalamus
What are the 3 sections of the brainstem?
midbrain, pons, medulla
What does the vestibulocochlear nerve transmit to the brain?
balance and auditory information
What is found in the inner ear and cochlea?
specialized hair cells
The vestibular and cochlear parts of the ear merge to form the…
vestibulocochlear nerve
Where does the vestibulochoclear nerve synapse?
in brainstem and thalamus
What is the modality of the vestibulocochlear nerve?
special sensory (balance and hearing)
What foramen does the vestibulocochlear nerve pass through?
internal acoustic meatus
Where does the vestibulocochlear nerve enter from?
enters brainstem between pons and medulla
What type of modality is the oculomotor nerve?
somatic motor and visceral motor
Where does the oculomotor nerve exit?
anterior side of midbrain
What is the modality of the trochlear nerve?
somatic motor
Where does the trochlear nerve exit?
posterior side of midbrain
What is the modality of the abducens nerve?
somatic motor
Where does the abducens nerve enter from?
between the pons and medulla
What do all three nerves (oculomotor, trochlear and abducens) pass through?
superior orbital fissure
What direction does each apex of the orbit osteology point in?
posteromedial
What kind of orientation do the apex cavity create in an orbit osteology?
oblique orientation
What are the 2 kinds of axes of the eye?
orbital and optical
How many bones contribute to each orbit?
7
Where is the optic canal located in the orbit?
at the apex
What are the 7 bones of the orbit osteology?
- frontal
- sphenoid
- ethmoid
- palatine
- lacrimal
- maxilla
- zygomatic
What are the 3 fossae of the orbit osteology?
superior orbital fissure
optic canal
inferior orbital fissure
How many extraocular muscles are there?
7
How many extraocular muscles attach to the eyeball?
6
What are the 3 rotational axes of the eye?
horizontal, vertical and anteroposterior
What are the names of the 7 extraocular muscles?
- medial rectus
- inferior rectus
- superior oblique
- inferior oblique
- superior rectus
- lateral rectus
- levator palpeerde superioris
What is the attachment site for the extraocular muscles?
common tendinous ring
What is the function of the levator palpebrae superioris muscle?
elevates the superior eyelid
Where does the levator palpebrae superioris attach to?
sphenoid bone
Which part of the eyeball do the rectus muscles attach to?
anterior part
Which part of the eyeball do the oblique muscles attach to?
posterior part
Where do the medial and lateral rectus attach?
common tendinous ring and anterior sclera on the medial and lateral sides
Which axis do the medial and lateral rectus contribute to?
vertical axis
What movement is produced by the medial rectus?
adduction
What movement is produced by the lateral rectus?
abduction
Where do the superior and inferior rectus muscles attach?
common tendinous ring and to the anterior sclera on the superior and inferior aspects
Which primary axis do the superior and inferior rectus muscles contribute to?
horizontal axis
What secondary axis do the superior and inferior rectus muscles contribute to?
A-P axis
What tertiary axis do the superior and inferior rectus muscles contribute to?
vertical axis
What actions does the superior rectus muscle perform?
elevation, intorsion, adduction
What actions does the inferior rectus muscle perform?
depression, extortion, adduction
Why do the superior and inferior rectus muscles perform multi axial actions?
because of the lack of alignment between the optical and orbital axes
Where does the superior oblique muscle attach to?
the sphenoid & passes through a fibrous sling (trochlea)
Where does the inferior oblique muscle attach to?
the maxilla on the anteromedial floor of the orbit
What is the primary, secondary and tertiary axes that the superior and inferior oblique muscles contribute to?
- A-P axis
- horizontal axis
- vertical axis
What actions does the superior oblique muscle perform?
intorsion, depression, abduction
What actions does the inferior oblique muscle perform?
extorsion, elevation, abduction
How can we test extraocular muscles?
H-test
what do we do to the optical axis with the line of pull for the SR/IR and SO/IO muscles?
we align them
How many degrees of abduction are required to align the optical axis with the line of pull for the superior and inferior rectus muscles?
23 degrees
Which muscle produces 23 degrees of abduction?
the lateral rectus
How many degrees of adduction are required to align the optical axis with the line of pull for the superior and inferior oblique muscles?
51 degrees
Which muscle produces 51 degrees of adduction?
medial rectus muscle
The oculomotor nerve provides somatic motor innervation to which muscles?
levator palpebrae superioris, superior
rectus, inferior rectus, medial rectus, + inferior oblique
muscles
The oculomotor nerve provides visceral motor innervation to which muscles?
sphincter muscles and ciliary muscles
Which muscle does the trochlear nerve provide innervation to?
superior oblique muscle
Which muscle does the abducens nerve provide innervation to?
lateral rectus muscle
CN III and VI pass ___ tendinous ring; CN IV passes ___.
through, above
Where does one of the eyes move to in oculomotor nerve palsy?
bottom corner
Where does one of the eyes move to in trochlear nerve palsy?
top corner
Where does one of the eyes move to in abducens nerve palsy?
towards the centre
Where does parasympathetic innervation of the eye come from?
oculomotor nerve
Where does the oculomotor nerve synapse in?
ciliary ganglion
What do the postganglionic oculomotor neurons form?
short ciliary nerves
Contraction of ciliary muscle ___ its internal diameter + lens becomes more rounded
decreases
Contraction of sphincter pupillae ____ pupil
constricts
Where does sympathetic innervation of dilator pupillae come from?
T1-T4 lateral horns
