Cranial Nerves Flashcards
Label the cranial nerves
What are the 2 origins of the cranial nerves?
I and II are extensions of the CNS
III to XII are part of the PNS and emerge from the brainstem
What is the relationship between the cranial nerves and the brainstem?
For each fibre type within a cranial nerve, there is a corresponding nucleus in the brainstem
This is a collection of cell bodies
What types of fibres are contained within the oculomotor nerve (CN III)?
Oculomotor nerve (CN III) carries 2 types of fibres, so it has two nuclei within the midbrain
it contains somatic motor fibres to the extraocular muscles coming from the oculomotor nucleus
it contains visceral motor (autonomic) fibres to the sphincter pupillae and ciliary muscles coming from the Edinger-Westphal nucleus
What happens to the fibres making up the oculomotor nerve as they leave the skull?
The fibres from the oculomotor and Edinger-Westphal nuclei merge together and exit the skull via the interpeduncular fossa as CN III
What section is shown?
How can you tell?
Midbrain
you can see the black cerebral peduncles at the back
the cerebral aqueduct (large white circle) is also visible
Where are the cranial nerve nuclei located within the brainstem?
Cranial nerve nuclei are scattered throughout the brainstem
Sensory nuclei are located laterally
Motor nuclei are located medially
All cranial nerve nuclei are located in the tegmentum
there are no nuclei in the tectum or basal surface
Complete the cross-section showing the general organisation of CN nuclei in the brainstem.
Which crosssection is shown?
This is a section through the rostral (open) medulla
the motor nuclei are located medially in the tegmentum
the sensory nuclei are located laterally in the tegmentum
What are the roles of the somatic and visceral sensory nuclei in the brainstem?
Somatic sensory:
- respond to sensations such as touch, pain and temperature
Visceral sensory:
- monitors the internal state of organs
- autonomic control
What are the 2 broad categories of nerve fibres carried in the cranial nerves?
Nerves of the head and neck carry either sensory (afferent) and/or motor (efferent) fibres
Each cranial nerve may carry several different fibre types
For each fibre type within a cranial nerve, there is a corresponding nucleus within the brainstem
What is a nucleus and where are they found?
A functional group of neurones within the CNS
They are located within the tegmentum of the brainstem
They are found within ALL brainstem parts
(midbrain, pons and medulla)
What is the difference between sensory and motor cranial nerve nuclei?
Sensory nuclei:
- receive information from fibres entering the brainstem in cranial nerves
- the cranial nerves synapse here
- they send fibres to the appropriate higher centre
motor nuclei:
- receive motor information from higher centres
- they synapse in the nuclei
- motor fibres originate here that leave the brainstem via cranial nerves
Why are cranial nerves I and II not typical cranial nerves?
They are derived from the forebrain, not the brainstem
What is the location and pathway of the olfactory nerve (I) like?
It originates from receptors in nasal mucosa
it enters the skull through the cribiform plate, where it merges with olfactory bulbs
the olfactory bulbs connect with olfactory tracts, which carry smell to other parts of the brain
THEY ARE EXTENSIONS OF THE TELENCEPHALON
What is the function of the olfactory nerve?
How can it be tested?
Special sensory - involved in olfaction (smell)
it is tested by offering a familiar smelling item (e.g. orange, coffee)
What is the location of the optic nerve like?
It emerges from the retina to enter the optic canal
this leads to the optic chiasma, where information form both eyes is sent to both sides of the brain
optic tracts then carry information to the thalamus
What is the function of the optic nerve?
Which foramen does it leave through?
Special sensory - vision
it leaves the skull via the optic canal
What is significant about the thalamus and sensory modalities?
All sensory modalities are sent to the thalamus first before being sent to the cortex
(except olfaction)
What is shown here?
CP - cribiform plate
OC - optic canal
OB - olfactory bulbs
Olf T - olfactory tracts
OT - optic tracts
ON - optic nerve
Where is the oculomotor nerve located?
Which foramen does it emerge from?
It is located at the pontomesencephalic junction
it leaves through the superior orbital fissure
What is the function of the oculomotor nerve?
How is it tested?
- Somatic motor to four extraocular muscles
- visceral (parasympathetic) motor to ciliary muscle and sphincter pupillae
- it is tested through the follow finger test
What is the location of the trochlear nerve?
What foramen does it leave through?
It is located at the dorsal midbrain
It leaves through the superior orbital fissure
What is the function of the trochlear nerve and how is it tested?
It supplies somatic motor innervation to the superior oblique muscle
- it is tested via the follow finger test
what is the location and foramen of the abducens nerve (VI)?
It is located at the pontomedullary junction
it leaves through the superior orbital fissure
What is the function of the abducens nerve?
how is it tested?
It supplies somatic motor function to the lateral rectus
it is tested via the follow finger test
What foramens and nerves are shown here?
Why are cranial nerves III, IV and VI linked together?
- They all supply the extraocular nerves
- they all exit via the superior orbital fissure of the sphenoid bone
Label the nerves and the muscles that they supply
III - oculomotor nerve:
- superior rectus
- inferior rectus
- inferior oblique
- medial rectus
- levator palpebrae superioris
IV - trochlear nerve:
- superior oblique
VI - abducens:
- lateral rectus
What muscles are involved in adduction and abduction of the eyes?
Abduction - lateral rectus
adduction - medial rectus
What muscles are responsible for the movements of the eyes
Which muscles are responsible for opening and closing the eyelids?
Closing the eyelids:
- orbicularis oculi (CN III)
Opening the eyelids:
- superior tarsal muscle (sympathetic)
- levator palpebrae superioris (CN III motor)
What muscles dilate and constrict the pupil?
Dilate the pupil:
- dilators of iris (sympathetic)
Constriction of pupil:
- sphincter pupillae - CN III parasympathetic
Changes lens:
- ciliary muscle changes the shape of the lens - CN III parasympathetic
What are the 3 divisions of the cranial nerve?
Where do they originate from?
V1 - opthalmic division
V2 - maxillary division
V3 - mandibular division
they all originate from the pons
Which foramina does the opthalmic division of the trigeminal nerve pass through?
What is their function and how are they tested?
Opthalmic division:
- foramen - superior orbital fissure
- provides somatic sensation from the upper face (above eye)
- tested with a cotton wool bud on the forehead and corneal reflex test
What foramina does the maxillary division of the cranial nerve pass through?
What is its function and how is it tested?
Maxillary division:
- foramen rotundum
- provides somatic sensation from middle face (between eye and mouth)
- tested with a cotton wool bud on the cheek
What foramen does the mandibular division of the trigeminal nerve pass through?
What is its function and how can it be tested?
Mandibular division:
- foramen ovale
- provides somatic sensation from the lower face, mandible and anterior 2/3 of the tongue
- provides somatic motor sensation to the muscles of mastication, anterior belly of diagastric and tensor tympani
- tested with a cotton wool bud on the jaw, clenching teeth for muscle mass and jaw jerk reflex
What foramina are shown?
Which divisions of the trigeminal nerve pass through them?
Superior orbital fissure:
- opthalmic division of trigeminal nerve (V1)
Foramen rotundum:
- maxillary division of trigeminal nerve (V2)
Foramen ovale:
- mandibular division of trigeminal nerve (V3)
What are the following divisions of the trigeminal nerve?
V1 opthalmic division - purple
V2 maxillary division - blue
V3 mandibular division - red
Which foramen are seen and which division of the trigeminal nerve passes through them?
Which area of the face do they supply sensory innervation to?
TG - trigeminal ganglion
This is a sensory ganglion containing cell bodies of sensory fibres
What are the four autonomic ganglia of the head and neck associated with the trigeminal nerve?
- Ciliary
- Pterygopalatine
- Submandibular
- Otic
Where is the location of the facial nerve?
Which foramen does it pass through?
Cerebellopontine angle
it enters the skull via the internal acoustic meatus
it leaves via the stylomastoid foramen
What is the function of the facial nerve (VII)?
- Somatic motor to muscles of facial expression, stapedius muscle and posterior belly of digastric
- special sensory as taste to the anterior 2/3 of the tongue
- somatic sensory to the skin of the ear
- visceral motor (parasympathetic) to all the glands except parotid
(Submandibular, sublingual, lacrimal)
What is the location of the vestibulocochlear nerve?
Which foramen does it pass out of?
what is its function?
- Located at cerebellopontine angle
- passes through the internal acoustic meatus
- special sensory function - hearing and balance
Which nerves and foramen are shown?
Internal auditory meatus
Label the components associated with the facial and vestibulocochlear nerves
What is the vestibular and cochlear system?
The vestibular system is involved in balance
the cochlear system is involved with hearing
What is the location and foramen of the glossopharyngeal nerve (IX)?
It is located in the posterolateral sulcus of the medulla, lateral to olives
It passes through the jugular foramen
What are the functions of the glossopharyngeal nerve (IX)?
- Somatic motor for swallowing (pharynx)
- visceral motor (parasympathetic) to parotid gland
- special sensory for taste on the posterior 1/3 of the tongue
- sensory to the middle ear, pharynx and posterior 1/3 of the tongue
- receives visceral sensation from the carotid body and carotid sinus, which monitor blood pressure and chemistry (CO2, O2)
How can the glossopharyngeal nerve (IX) be tested?
Gag reflex
stimulation of the pharynx causes the muscles to contract, showing that sensory information is being received
What is the location and the foramen of the vagus nerve (X)?
Located in the posterolateral sulcus of the medulla, lateral to the olives
Leaves via the jugular foramen
What are the functions of the vagus nerve (X)?
- Somatic motor to muscles of the pharynx and larynx and muscles of the soft palate (Uvula)
- Visceral motor (parasympathetic) to thoracic and GI tract (and visceral sensory)
- Special sensory test from the epiglottis and soft palate
- somatic sensation from epiglottis, skin of external ear and larynx
How is the vagus nerve tested?
Through speaking and movement of the uvula
Which nerves are shown here?
Which foramen do they pass out of?
Jugular foramen
Which nerves are shown here?
What is indicated by the different colours?
The carotid body is located at the bifurcation of the common carotid artery
information about blood pressure and chemistry are carried to the CNS via the glossopharyngeal nerve IX
the different colours represent the many nuclei of CN IX and X
What is the location and foramen of the accessory nerve (XI)?
It is located at the caudal medulla and rostral spinal cord
It passes through the jugular foramen
What is the function of the accessory nerve (XI)?
How can it be tested?
It provides somatic motor to the sternocleidomastoid and trapezius muscles
it is tested by shrugging the shoulder and rotating the head
WHat is the location and the foramen of the hypoglossal nerve (XII)?
It is located in the anterolateral sulcus (between pyramid and olives)
It passes through the hypoglossal canal
What is the function of the hypoglossal nerve?
How can it be tested?
It provides somatic motor to the muscles of the tongue
It is tested by asking the patient to protrude the tongue
What nerves are shown here?
Which foramen do they pass out of?
XI passes out of the jugular foramen
XII passes out of the hypoglossal canal
Which nerves and features are shown here?
What is significant about the spinal accessory nerve?
CV XI is formed by spinal roots from C1 - C5
these fuse together and pass through the foramen magnum into the skull
they then fuse with the cranial root and leave the skull via the jugular foramen
How does the tongue move in hypoglossal nerve paralysis?
Why?
The tongue will deviate towards the paralysed side when the hypoglossal nerve is injured
this is due to the muscle on the injured side being paralysed and not contracting
What nerves innervate the tongue?
What are the 4 cranial nerves containing autonomic fibres?
What are the ganglia they supply in the head and neck and their functions?
Ciliary ganglia:
- comes from CN III
- functions in pupil constriction - sphincter pupillae
Pterygopalatine ganglia:
- comes from CN VII
- involved in lacrimation - lacrimal gland
Submandibular ganglion:
- comes from CN VIII
- involved in salivation - submandibular and sublingual glands
Otic ganglion:
- supplies parotid gland
- Vagus nerve X supplies the viscera
How do the autonomic fibres from the cranial nerves reach their destination?
They pass from their ganglia to the respective organ by “piggy-backing” on branches of the trigeminal nerve
Complete the table
