Cranial Nerves Flashcards
What are cranial nerves?
12 paired nerves
Connected to brain
What do cranial nerves supply?
Somatic and visceral motor and and sensory info to head
CN IX and X also supply visceral sensory and motor innervation to neck, chest, and abdomen
What is cranial nerve I?
Olfactory
What is cranial nerve II?
Optic
What is cranial nerve III?
Oculomotor
What is cranial nerve IV?
Trochlear
What is cranial nerve V?
Trigeminal
What is cranial nerve VI?
Abducent
What is cranial nerve VII?
Facial
What is cranial nerve VIII?
Vestibulocochlear
What is cranial nerve IX?
Glossopharyngeal
What is cranial nerve X?
Vagus
What is cranial nerve XI?
Accessory?
What is cranial nerve XII?
Hypoglossal
Which cranial nerves are purely sensory?
CN I
CN II
CN VIII
Which cranial nerves are purely motor?
CN III CN IV CN VI CN XI CN XII
Which cranial nerves are mixed?
CN V
CN VII
CN IX
CN X
What are cranial nerves connected centrally to?
Cranial nerve nuclei
Which cranial nerves are associated with the brainstem?
CN III to CN XII
How are cranial nerves organised?
Rostral to caudal roughly in order of target tissues they’re associated with
On which surface do cranial nerves exit?
All exit ventrally
Except CN IV - exits dorsally
Which cranial nerve crosses over before leaving the brain?
CN IV
From where do motor nerves exit?
Located medially
Exit close to midline
How are the motor nerve nuclei organised?
In 3 columns close to midline
What are the three motor nerve nuclei columns, from medial to lateral?
Somatic
Branchial
Visceral
Which nerves have somatic motor fibres?
CN III
CN IV
CN VI
CN XII
Which nerves have branchial motor fibres?
Mandibular division of CN V
CN VII
CN IX
CN X
What is the nucleus ambiguus?
Mostly motor nucleus
Lies behind inferior olive
Sends fibres to stylopharyngus via CN IX
Sends fibres to levator palati via CN X
Which nerves have visceral efferents?
CN III
CN VII
CN IX
CN X
From which nucleus do autonomic fibres of CN III originate?
Edinger-Westphal nucleus
From which nucleus do autonomic fibres of CN VII originate?
Superior salivatory nucleus
From which nucleus do autonomic fibres of CN IX originate?
Inferior salivatory nucleus
From which nucleus do autonomic fibres of CN X originate?
Dorsal motor nucleus of vagus
How are the sensory nuclei organised?
3 columns laterally
What are the three columns of sensory nuclei, from medial to lateral?
Visceral sensory
Somatic sensory
Special sensory
Which nerves have visceral afferents?
CN VII
CN IX
CN X
Which nerves are sometimes called special visceral afferents, and why?
For taste
- CN VII
- CN IX
- CN X
What is the nucleus solitarius?
Extends from pons to level of nucleus gracilis
Rostral = gustatory nucleus
- VII, IX, X: Primary afferents receiving input from taste buds and palate
Caudal = visceral sensory division
- X: Afferents from heart and abdominal viscera
- IX: Baroreceptors and chemoreceptors from carotid body and sinus
What are the special senses and their corresponding cranial nerves?
Smell = CN I - olfactory
Sight = CN II - optic
Hearing and equilibrium = CN VIII - vestibulocochlear
Which cranial nerves originate from the midbrain?
CN III
CN IV
Which cranial nerves originate from the pons?
CN V
CN VI
CN VII
CN VIII
Which cranial nerves originate from the medulla?
CN VIII
CN IX
CN X
CN XII
What are the functions of the olfactory nerve (CN I)?
Special sensory - sense of smell
Where does the olfactory nerve exit the skull?
Cribiform plate of the ethmoid bone?
Where is the olfactory cortex?
In insula
What are the functions of the optic nerve (CN II)?
Special sensory - vision
Where does the optic nerve exit the skull?
Optic canal in sphenoid bone
Where does the optic nerve synapse in the thalamus?
Lateral geniculate nucleus
What happens at the optic chiasm?
Some axons cross here
Where does information from the lateral geniculate nucleus go?
Visual cortex
How many extraocular muscles are there?
6
What are the extraocular muscles?
Rectus muscles - Superior rectus - Inferior rectus - Lateral rectus - Medial rectus Oblique muscles - Superior oblique - Inferior oblique
Which cranial nerves go to the extraocular muscles?
CN III
CN IV
CN VI
What do the cranial nerves innervating the extraocular muscles do?
Act in coordinated fashion
Where do CN III, CN IV, and CN VI exit the skull?
Superior orbital fissure, between the wings of the sphenoid bone
What is the oculomotor nerve (CN III)?
Somatic motor - Medial rectus - Superior rectus - Inferior rectus - Inferior oblique Visceral motor - Iris (pupils) - Ciliary muscle (focusing)
What are the nuclei of the oculomotor nerve?
Somatic motor: oculomotor nucleus near midline
Visceral motor: lateral to somatic motor nucleus
Which cranial nerves enter the orbit?
CN III
CN IV
CN VI
CN V1
How do all structures enter the orbit from the skull?
Via superior orbital fissure
Why is it relevant that cranial nerves often exit in groups?
Affected in disease together
What nerves exit from the cribiform plate?
Olfactory nerve
What nerves exit from the optic canal?
Optic nerve
What nerves exit from the superior orbital fissure?
Oculomotor nerve
Trochlear nerve
Ophthalmic branch of trigeminal nerve
What nerves exit the auditory canal?
Facial nerve
Vestibulocochlear nerve
What nerves exit the jugular foramen?
Glossopharyngeal nerve
Vagus nerve
Accessory nerve
What nerves exit the hypoglossal foramen?
Hypoglossal nerve
What is the pupillary light reflex?
Sensory inputs to brain from retina via CN II
Motor outputs to sphincter pupillae muscle in iris
Which nucleus provides the parasympathetic fibres in the oculomotor nerve?
Edinger Westfal nucleus
What is the pupillary light reflex used for?
To test midbrain function
What is the trigeminal nerve (CN V)?
Somatic sensory
Branchial mtoro
What are the functions of the trigeminal nerve?
Sensory: input from face, inside of mouth, and soft palate
Motor: muscles of mastication, and tensor tympani in inner ear
With which branch of the trigeminal nerve do its motor fibres travel?
Mandibular branch
What does the tensor tympani do?
Dampen sound from chewing
Where is the tensor tympani muscle?
In inner ear
Where are the trigeminal nuclei?
From midbrain to upper spinal cord
What are the nuclei of the trigeminal nerve?
Mesencephalic - mostly proprioception
Chief sensory - mostly fine touch
Spinal trigeminal - particularly important for pain
Motor
What is the pathway for somatosensory information from the face?
Primary nerve = trigeminal nerve > synapses in trigeminal nucleus
Secondary nerve crosses midline > passes up brainstem > thalamus
Tertiary nerve from thalamus > cortex
How does the trigeminal nerve exit the brainstem?
As two roots
- Motor
- Sensory
Which ganglion do the trigeminal sensory nerves travel to?
Trigeminal ganglion
What are the branches of the trigeminal nerve?
Ophthalmic - eyes, nose, and forehead
Maxillary - cheeks
Mandibular - jaw, teeth, and tongue
What foramina does the trigeminal nerve exit the skulll through?
V1 = superior orbital fissure V2 = foramen rotundum V3 = foramen ovale
What is the corneal blink reflex?
Sensory: CN V1
Motor: to eyelid by CN VII
What is the corneal blink reflex used for?
Test of pontine function
What type of nerve is the facial nerve (CN VII)?
Branchial motor
Visceral effernt
Visceral sensory
Somatic sensory
What are the roles of the facial nerve?
Motor
- Innervates muscles of facial expression
- Stapedius muscle in ear
- Part of digastric muscle
What is the function of the stapedius muscle?
Dampens sound if it’s too loud
What is the most common cause of CN VII loss of function?
Bell’s palsy
What is nervus intermedius?
Branch of facial nerve
What is the function of nervus intermedius?
Parasympathetic
- Lacrimal glands
- Sublingual and submandibulary salivary glands
Taste
- From anterior 2/3 of tongue and soft palate
Sensation
- From small region near external auditory meatus
Which branch of the facial nerve innervates the lacrimal glands?
Greater petrosal
Which branch of the facial nerve carries taste information from the tongue?
Chorda tympani
Through which foramen does the facial nerve exit the skull?
Stylomastoid foramen
What are the five terminal branches of the facial nerve?
Temporal Zygomatic Buccal Mandibular Cervical
What is the function of the five terminal branches of the facial nerve?
Motor innervation for the muscles of facial expression
What is the course of the facial nerve?
Brainstem > passes internal acoustic meatus > greater petrosal branch > branch to stapedius > chorda tympani branch > exits skull through stylomastoid foramen > posterior auricular branch > terminal branches
What is the relationship between the terminal branches of the facial nerve and the parotid gland?
Go through parotid but don’t innervate it
What type of nerve is the vestibulocochlear nerve (CN VIII)?
Special sensory - hearing and balance
What are the nuclei of the vestibulocochlear nerve?
Dorsal and ventral cochlear nuclei
Four vestibular nuclei
Which division of the brainstem are the nuclei of the vestibulocochlear nerve located in?
On border of pons and medulla
Where does the vestibulocochlear nerve exit the skull?
Internal acoustic meatus
What type of nerve is the glossopharyngeal nerve (CN IX)?
Somatic sensory
Special sensory - taste
Visceral motor
Motor
What are the functions of the glossopharyngeal nerve?
Sensory - Posterior 1/3 of tongue - Pharynx - Middle ear - Carotid body Taste - Posterior 1/3 of tongue Visceral motor - Parasympathetic to parotid gland Motor - Stylopharyngeus
Where does the glossopharyngeal nerve exit the skull?
Jugular foramen
What is the course of the glossopharyngeal nerve?
Rootlets from different columns of brainstem > jugular foramen lateral and in front of CN X and CN XI > superior and inferior sensory ganglia > between internal and external carotid arteries > follows stylopharyngeus to oropharynx and tongue
What type of nerve is the vagus nerve (CN X)?
Branchial motor Visceral motor Somatic sensory Visceral sensory (special) taste Visceral sensory (general)
What is the most important function of the vagus nerv?
Autonomic
Which branch of the vagus nerve innervates the vocal cords?
Recurrent laryngeal nerve
What are the motor functions of the vagus nerve?
Many striated muscles
- Soft palate
- Pharynx
- Larynx
- Upper oesophagus
- 1 tongue muscle
What are the parasympathetic functions of the vagus nerve?
Many
- From pharynx to upper abdomen
What are the sensory functions of the vagus nerve?
Pharynx
Larynx
Oesophagus
What are the visceral sensory functions of the vagus nerve?
Input from baroreceptors and chemoreceptors of aortic arch
Taste from epiglottis and pharynx
What is the gag reflex?
Sensory: CN IX
Motor: CN X
What is the gag reflex used for?
Test medullary function
Where is the nucleus of the accessory nerve?
Upper 5-6 of cervical spinal cord
What is the course of the accessory nerve?
Enters cranium via foramen magnum
Travels with X roots
Exits via jugular foramen
What type of nerve is the accessory nerve (CN XI)?
Motor
What is the function of the accessory nerve?
Motor input to sternomastoid and upper part of trapezius
In general, structures on which side do cranial nerves relate?
Ipsilateral
What is the exception to the ipsilateral relationship of structures and cranial nerves?
Trochlear nerve - crosses before exiting midbrain
What type of motor neuron are cranial nerves innervating muscle?
Lower motor neurons
What type of nerve is the hypoglossal nerve (CN XII)?
Somatic motor
What are the functions of the hypoglossal nerve?
Motor innervation to intrinsic and extrinsic muscles of tongue
Which muscle of the tongue doesn’t the hypoglossal nerve innervate?
Palatoglossus - innervated by CN X
Where does the hypoglossal nerve exit the skull?
Hypoglossal foramen
