Cranial Nerves Flashcards
What are the 3 special sensory cranial nerves?
CN I - olfactory
CN II - optic
CN VIII - vestibulocochlear
What are the 5 motor cranial nerves?
CN III - oculomotor CN IV - trochlear CB VI - abducent CN XI - spinal accessory CN XII - hypoglossal
What are the 4 cranial nerves with both motor and sensory function?
CN V - trigeminal
CN VII - facial
CN IX - glossopharyngeal
CN X - vagus
What part of CNS is CN I connected to?
Forebrain
What part of CNS is CN II connected to?
Forebrain
What part of CNS is CN III connected to?
Midbrain
What part of CNS is CN IV connected to?
Midbrain
What part of CNS is CN V connected to?
Pons
What part of CNS is CN VIconnected to?
Pons and medulla junction
What part of CNS is CN VII connected to?
Pons and medulla junction
What part of CNS is CN VIII connected to?
Pons and medulla junction
What part of CNS is CN IX connected to?
Medulla
What part of CNS is CN X connected to?
Medulla
What part of CNS is CN XI connected to?
Spinal cord
What part of CNS is CN XII connected to?
Medulla
What is the only CN that originates from posterior surface of brainstem?
Trochlear (CN IV)
Which is the only CN sensory modality that does not synapse in the thalamus prior to reaching the cortex?
CN I (olfactory nerve)
What part of brain is olfactory info processed in?
Posterior inferior frontal lobes + anterior medial temporal lobes
In the brainstem opening, motor nerves are medial and sensory lateral. True/false?
True
Aside from its somatic motor function to the eye muscles, what other function does the CN III nerve carry?
parasympathetic axons to sphincter pupillae and ciliary muscle
What is the function of the trochlear nerve?
Motor control to superior oblique muscles of eye
What CNs nuclei are in the midbrain?
CN III and IV
What CNs nuclei are in the pons?
CN V, VI, VII, VIII
What CNs nuclei are in the cerebrum?
CN I and II
What CNs nuclei are in the medulla oblongata?
CN IX, X, XI, XII
What is the function of the abducens nerve?
lateral rectus muscle of eyes
What is the function of the hypoglossal nerve?
motor control of tongue muscles except for palatoglossus
What is the unique pathway of the nerves leaving the spinal accessory nucleus?
Rootlets branch off spinal cord C1-C5 travelling up through foramen magnum and back out through jugular foramen
What muscles does the spinal accessory nerve innervate?
sternocleidomastoid and trapezius
What is the nucleus ambiguus and what is the name of its nerve?
Its the portion of the spinal accessory nerve that is in the medulla oblongata and its nerve is called the cranial accessory nerve
What is the pathway of the cranial accessory nerve?
Nucleus in medulla oblongata, joins with spinal accessory at jugular foramen then branches off to join vagus nerve
What are the 3 functions of the trigeminal nerve (CNV)?
- Somatosensation of face
- proprioception of chewing
- motor control of mastication, tensor tympani, mylohyoid, anterior belly of digastric, tensor veli palatini
Where is the trigeminal motor nucleus?
In the pons
Where are the trigeminal sensory nuclei?
along a column of neurons that stretches from midbrain down to the upper 2 segments of the cervical spinal cord
What are the 3 functions of the 3 parts of the trigeminal sensory nuclei column? (superiorly -> inferiorly)
- proprioception
- discriminative touch, vibration sense
- pain & temperature
What are the 3 parts of the trigeminal sensory nuclei column? (superiorly->inferiorly)
- mesencephalic nucleus
- pontine trigeminal nucleus (principal one)
- spinal nucleus
What is unique about the mesencephalic nucleus?
its axons don’t synapse in a ganglion prior to entering CNS, only place in body where primary afferent sensory neurons are in CNS
What fibres deliver info from trigeminal sensory nuclei to what specific nucleus in the thalamus?
- Ventral trigeminothalamic tract
- to ventroposteriomedial nucleus of thalamus
What causes oral sparing when there is a lesion along spinal nucleus of the trigeminal sensory nuclei?
Because innervation of the face is arranged in rings starting smallest at the mouth outwards. The fibres innervating the smaller circles around mouth sit higher up the spinal nucleus so a lesion below will not affect them.
What are the 3 functions fo the facial nerve (CN VII)?
- motor: facial expression + stapedius
- parasympathetic to pterygopalatine and submandibular ganglia
- taste (anterior 2/3 tongue via c.tympani)
What are the 4 functions of the glossopharyngeal nerve (CN IX)?
- touch, pain and temp from posterior tongue, pharyngotympanic tube and upper pharynx
- taste (posterior 1/3 tongue)
- parasympathetic to otic ganglion (parotid gland)
- motor to stylopharyngeus
What are the 4 functions of the vagus nerve (CNX)?
- touch, pain and temp from pharynx, larynx, trachea, oesophagus, thoracic and abdominal viscera
- taste (epiglottis)
- parasympathetic for ganglia to thoracic and abdominal viscera
- motor to striated muscle of pharynx and larynx
What nerve contributes to CN X vagus function of motor control to striated muscle of pharynx and larynx?
Cranial accessory nerve
What is unique about the axons of the facial motor nuclei?
they loop around the abducens nucleus
What nucleus do the facial parasympathetic fibres travel from?
salvitory nucleus
What nucleus do the facial taste fibres travel to?
solitary nucleus
What is minor 4th component of facial nerve and what is the name of its nucleus?
- small region of somatosensation associated with ear
- spinal trigeminal nucleus
What is the ganglion for facial nerve taste fibres called?
Geniculate ganglion
What nucleus do the glossopharyngeal taste fibres travel to?
Solitary nucleus
What nucleus do the glossopharyngeal touch fibres travel to?
Spinal trigeminal tract & nucleus
What nucleus do the glossopharyngeal parasympathetic fibres travel to?
salivatory nucleus
What nucleus do the glossopharyngeal motor fibres of stylopharyngeus muscle travel from?
nucleus ambiguus
What nucleus do the vagus preganglionic parasympathetic fibres travel from?
dorsal nucleus AKA motor nucleus
What nucleus do the vagus taste (epiglottis) fibres travel to?
solitary nucleus
What nucleus do the vagus somatosensation fibres travel to?
spinal trigeminal nucleus
What nucleus do the vagus motor fibres travel from?
nucleus ambiguus
Which nucleus do preganglionic vagal fibres that innervate the heart come from?
Nucleus ambiguus
What is the name of the efferent motor supply to cranial nerves? (i.e. the motor info coming from brain to cranial nerves)
corticobulbar tract
Which portion of the face is controlled by bilateral facial motor nerve input and by contralateral facial motor nerve input? Why is this clinically significant?
Upper portion - bilateral
lower portion - contralateral
-if stroke in motor cortex, only lower portion of contralateral face will be affected
Where does parasympathetic info for cranial nerves come from in brain?
preganglionic fibres from hypothalamus, some synapse in reticular formation and some go straight to CN
What is the reticular formation?
network of cell bodies, axons and dendrites in the middle of the brainstem (it isn’t part of the long pathways e.g. corticospinal tract and cranial nerve nuclei)
Reticular formation functions? (6)
- integrate cranial nerve reflexes,
- pain,
- influence voluntary movement,
- regulates autonomic activity,
- helps with breathing and sleep,
- can activate the cerebral cortex
What is the result of a medial bilateral lesion of the brainstem reticular formation at/above the upper pons? and why?
- causes irreversible coma
- interrupts Ascending reticular activating system which is major control of keeping brain conscious
