Anatomy of Cranial Nerves Flashcards
CNI is what kind of nerve?
special sensory
CNII is what kind of nerve?
special sensory
CN III is what kind of nerve?
motor and parasympathetic
CN IV is what kind of nerve?
motor
CN V is what kind of nerve?
CN V1= sensory
CN V2= sensory
CN V3 = sensory & motor
CN VI is what kind of nerve?
motor
CN VII is what kind of nerve?
special sensory, motor & parasympathetic
CN VII is what kind of nerve?
special sensory, motor and parasympathetic
CN X is what kind of nerve?
Sensory motor and parasympathetic
CN XI is what kind of nerve?
motor
CN XII is what kind of nerve?
motor
Where is the extra cranial part of the olfactory nerve?
within olfactory mucosa in nasal cavity
Which cranial foramina does the olfactory nerve pass through?
cribriform plate of the ethmoid bone
Where does the olfactory nerve connect with the CNS?
Synapse in the olfactory bulb
Pass through the olfactory tract to cortical areas
Where is the extra cranial part of the optic nerve?
Neurons of the retina travel posteriorly via optic nerve from the posterior hemisphere of eye through the orbit
Which cranial foramina does the optic nerve pass through?
Optic nerve passes through the optic canal in the middle cranial fossa
What is the intracranial part of the optic nerve?
Travels around the pituitary stalk to optic chiasm to form the optic tract
Where does the optic nerve connect with the CNS?
Diencephalon
How would you test CN I?
ask a patient to smell a familial smell while covering the contralateral nostril
How can you test CN II?
- acuity (snellen charts)
- colour (Ishihara plates- colour blindness)
- fields (four quadrants)
- reflexes (pupillary light reflexes)
- fundoscopy
Where is the oculomotor nerves connection to the midbrain?
midbrain (mesencephalon)
Where is the intracranial part of the oculomotor nerve?
Travels towards the orbit in the lateral wall of the cavernous sinus
What cranial foramina does the oculomotor nerve travel through?
superior orbital fissure (SOF)
What is the extra cranial part of the oculomotor nerve?
Passed through SOF into orbit and supplies ALL extra ocular muscles except two.
Parasympathetics synapse in the ciliary ganglion.
How would you test CNIII parasympathetics?
Use a light to check for pupillary constriction
Where does the trochlear nerve connect with the CNS?
Midbrain (mesencephalon)
Describe the intracranial part of the trochlear nerve
Travels towards the orbit in the lateral wall of the cavernous sinus
Which cranial foramina does the trochlear nerve pass through?
SOF
Describe the extra-cranial path of the trochlear nerve
Passed through the SOF into orbit and supplies only the superior oblique muscle
Where is the abducent nerves connection with the CNS?
Pontomedullary junction
Describe the intracranial part of the abducent nerve?
Travels towards the orbit within the cavernous sinus
Which cranial foramina foes the abducent nerve pass through/
SOF
describe the extra cranial path of the abducent nerve?
Passed through SOF into orbit and supplies only the lateral rectus muscle
Which cranial nerves does the H test look at?
CNs III, IV, VI
Describe the extra-cranial part of the vestibulocochlear nerve?
Axons from cochlear and vestibular apparatus
Which cranial foramina does the vestibulocochlear nerve pass through?
Internal acoustic meatus
In posterior cranial fossa
Describe the intracranial part of the vestibulocochlear nerve?
Travels posteromedially from the internal acoustic meatus to the pontomedullary junction
Where does the vestibulocochlear nerve connect with the CNS?
Pontomedullary junction
How can the vestibulocochlear nerve be tested clinically?
Rinne and Weber tests
Where does CN XI connect with the CNS?
Cervical spinal cord
Describe the intracranial part of the spinal accessory nerve?
Ascends through foramen magnum then travels towards jugular foramen in posterior cranial fossa
Which cranial foramina does the spinal accessory nerve pass through?
Jugular foramen in the posterior cranial fossa
Describe the extra-cranial part of the spinal accessory nerve?
Axons supply sternocleidomastoid on the deep surface, then continue across the posterior triangle to supply trapezius and sternocleidomastoid.
How can the spinal accessory nerve be tested clinically?
Ask patient to shrug their shoulders
Ask patient to turn head to flex neck and turn towards the opposite side
The cutaneous nerves of the cervical plexus also pass ____ to the ________ of the posterior border of SCM (at the ‘_____ _____’ of the neck)
But they do not pass ____ to _______
The cutaneous nerves of the cervical plexus also pass deep to the midpoint of the posterior border of SCM (at the ‘nerve point’ of the neck)
But they do not pass deep to trapezius
Where does the hypoglossal nerve connect to the CNS?
Via mainly rootlets lateral to the pyramids of the medulla oblongata
Describe the intracranial part of the hypoglossal nerve
Passes anteriorly to hypoglossal canal
Which cranial foramina does the hypoglossal nerve pass through?
Hypoglossal canal in the posterior cranial fossa
Describe the extra-cranial part of the hypoglossal nerve
Descends lateral to the carotid sheath
At the level of the hyoid turns anteriorly towards lateral aspect of tongue
Supplies most of the muscles of the tongue
CN XII innervates all muscles ending in glossus except the ____________.
CN XII innervates all muscles ending in glossus except the palatoglossus.
How can hypoglossal nerve be tested clinically
Ask patient to stick tongue out
If both CNXII’s are functioning normally the tongue tup remains on the midline on protrusion.
If there is unilateral CNXII pathology the tongue tip will point ______ the side of the injured nerve
If there is unilateral CNXII pathology the tongue tip will point towards the side of the injured nerve
Where do all three branches of the trigeminal nerve connect with the CNS?
Pons (laterally, midway between midbrain and medulla)
Describe the intracranial part of CN V
Inferior to the edge of the tentorium cerebella between the posterior and middle cranial fossa
Which cranial foramina do the devisions of CN V pass through?
CN V1- SOF
CN V2- foramen rotundum
CN V3- foramen ovale
Describe the extra-cranial part of CN V?
Sensory axons course from the superficial and deep structures of the face, posteriorly, towards their respective foramen.
Motor axons from CN V3 course from the foramen ovale towards the skeletal muscle they supply.
What is supplied superficially by CNV1?
- Upper eyelid
- cornea (corneal reflex)
- all conjunctiva
- skin of root/bridge/tip of nose
What is supplied superficially by CNV2?
- skin of lower eyelid
- skin over maxilla
- ski of ala of nose
- skin/mucosa of the upper lip
What is supplied superficially by CNV3?
Skin over mandible and temporomandibular joint (apart from the angle of the mandlble)
what supplies the skin over the angle of the mandible?
Great auricular nerve (C2, 3)
Also supplies some external ear
What is the deep sensory territory of CN VI?
- Bones & soft tissues of the orbit (except the orbital floor & lower eyelid)
- Upper anterior nasal cavity
- Paranasal sinuses (except the maxillary sinus)
- Anterior & posterior cranial fossae
What is the deep sensory territory of CN V2?
- Lower posterior nasal cavity
- Maxilla & maxillary sinus
- Floor of the nasal cavity/palate
- Maxillary teeth & associated soft tissues (gingivae & mucosae)
What is the deep sensory territory of CN V3?
- Middle cranial fossa
- Mandible
- Anterior 2/3rds of the tongue
- Floor of the mouth
- Buccal mucosa
- Mandibular teeth & associated soft tissues
What does CNV3 provide motor innervation to?
3 pairs of jaw closing muscles
- masseter
- temporalis
- medial pterygoid
1 pair of jaw opening muscles
- lateral pterygoid
Tensor veli palatini
Tensor tympani
How would you test the sensory function of the trigeminal nerve?
- Ask the patient to close their eyes
- Gently brush the skin in each dermatome with a fine tip of cotton wool
- Ask the patient to tell you when they feel their skin being touched
- Compare the 2 sides
How would you test the motor function of the trigeminal nerve?
- Palpate the strength of contraction of the masseter & temporalis by asking patient to clench their teeth
- Ask the patient to open their jaw against resistance
____ _______ _____ form the first part of the afferent limb of the blink reflex.
long ciliary nerves form the first part of the afferent limb of the blink reflex.
Where does the facial nerve connect to the CNS?
Anterolateral pontomedullary junction
Describe the intracranial part of CN VII
Directly into internal acoustic meatus in the posterior cranial fossa
Which cranial foramen does the facial nerve pass through?
Internal acoustic meatus (in) Stylomastoid foramen (out)
Describe the extra cranial part of the facial nerve?
Most somatic motor axons pass into the parotid gland then into 6 branches that supply the muscles of facial expression
The facial nerve courses through the _____ ____ of the temporal bone
The facial nerve courses through the petrous part of the temporal bone
What does the chorda tympani supply?
taste buds of the anterior 2/3rds of the tongue
Parasympathetic supply to the submandibular and sublingual glands
What is the function of the stapedius muscle?
Smallest skeletal muscle in the body- reduces staled movement to protect the internal ear from excessive noise
Which nerve supplies parasympathetics to the pterygopalatine ganglion?
CN VII links lacrimal and mucous glands of the midface
Which nerve does the chorda tympani join to supply the submandibular gland?
lingual nerve
How can CN VII be tested ?
ask patient to:
- Raise eyebrows
- Close eyes tightly
- Smile
- Puff out cheeks and hold air
Where does the glossopharyngeal nerve connect with the CNS?
Lateral aspect of superior medulla oblongata
Describe the intracranial part of glosspharyngeal nerve?
Directly towards jugular foramen in the posterior cranial fossa
Which foramen does the glossopharyngeal nerve pass through?
Jugular foramen
Describe the extra cranial part of the glossopharyngeal nerve
Descends towards pharynx and mouth
- to the stylopharyngeus muscle
- to the parotid gland
- from pharyngeal mucosa
- from carotid body and sinus
- from posterior 1/3rd of tongue
What does the glossopharyngeal nerve supply general sensory innervation to?
- posterior 1/3rd of tongue
- mucosa of most of the nasopharynx and oropharynx
- mucosa of some of the laryngopharynx (some overlap with CN X territory)
- the palatine tonsil
- the Eustachian tube
- the middle ear cavity
What does the glossopharyngeal nerve supply special sensory innervation to?
-vallate papillae (with taste buds) of the posterior 1/3rd of the tongue
What does the glossopharyngeal nerve supply visceral afferent innervation to?
Carotid sinus baroreceptors and the carotid body chemoreceptors
What does the glossopharyngeal nerve supply somatic motor innervation to?
Stylopharyngeus
What does the glossopharyngeal nerve supply parasympathetic innervation to?
Secretomotor to the parotid glands
How is CN IX clinically testable?
- CN IX general sensory axons from the above territory form the afferent limb of the gag reflex
CN IV general sensory afferents are commonly associated with ________ ____ from the ______ to the ___ and vice versa
CN IV general sensory afferents are commonly associated with referred pain from the pharynx to the ear and vice versa
Where does the vagus nerve connect to the CNS?
Lateral aspect of medulla oblongata, immediately inferior to CN ix
Describe the intracranial part of the vagus nerve
Directly towards jugular foramen in the posterior cranial fossa
Which cranial foramina does the vagus nerve pass through?
Jugular foramen
Describe the extra cranial part of the vagus nerve
Axons supply lots of structures between the palate and the midgut
Describe the path of the vagus nerve in the neck
Runs within the carotid sheath- posterior to and between the common carotid artery and jugular vein
Describe the path of CN X in the thorax
Runs into the thorax then gives off the recurrent laryngeal nerve to turn back superiorly and supply the muscles of the larynx
Left recurrent laryngeal nerve curves ____ the ____ __ ___ ____
Left recurrent laryngeal nerve curves under the arch of the aorta
Right recurrent laryngeal nerve curves ____ the _____ _______ ____
Right recurrent laryngeal nerve curves under the right subclavian artery
Where does the vagus nerve run through the chest?
Right CN X on lateral aspect of trachea
Left CN X on lateral aspect of aortic arch
Both pass posterior to lung root and onto oesophagus
Both pass through diaphragm with oesophagus
Both CN Xs pass onto the surface of the ____ and then provide branches to the; spleen…
Both CN Xs pass onto the surface of the stomach and then provide branches to the; spleen, pancreas, kidney, midgut (in the mesenteries) and lastly splenic flexure of colon
Branches of the CNX in the abdomen pass to the ____ and ___ _____ ganglia
Branches of the CNX in the abdomen pass to the celiac and superior mesenteric ganglia
How can CN X be clinically tested?
Ask patient to say ‘ahhhhh’ – also tests CNV3
(MUSCLES OF PALATE)
Motor function
-Uvula should lift straight up in midline
Ask patient to swallow small amount of water (PHARYNGEAL MUSCLES)
- Watch larynx movement
- Splutter may suggest abnormal swallow
Listen to speech
(LARYNGEAL MUSCLES)
-Hoarseness may suggest abnormal function of muscles of larynx
Unilateral CN X pathology will pull uvula ___ the non-functioning side
Unilateral CN X pathology will pull uvula AWAY from the non-functioning side
