Flashcards in Motor/Parasympathetic Cranial Nerves - V, VII, IX, X, XI, XII (15) Deck (53)
What mnemonic device can you use to remember which cranial nerves have motor, sensory, or mixed functions?
Some Say Marry Money But My Brother Says Big Business Makes Money; sensory -S, Mixed - M, both - B (duh)
Which 5 cranial nerves are purely motor?
Which four cranial nerves have a parasympathetic component?
Occulomotor, Facial, Glossopharyngeal, Vagus (3, 7, 9, 10)
Where do the nuclei of CN V reside?
At the mid pons level - CN V also exits the brainstem at this level, on the anterolateral surface of the pons
What nerve do motor fibers of CN V travel with? Through what foramen do they exit the calvarium?
Mandibular branch (V3) of trigeminal - exit via foramen ovale
What muscles do the motor fibers of CN V (trigeminal) innervate? (General group, two examples for bonus)
Muscles of mastication, including mastered and temporalis muscles
What mediates the afferent branch of the jaw jerk reflex? Where does it synapse?
Sensory fibers of V3 --> mesencephalon nucleus of V
(Muscle spindle from masseter muscle)
What nerve mediates the efferent branch of the jaw jerk reflex?
Motor division of V3 (short interneuron connects with the motor nucleus of V from the mesencephalon nucleus)
What would the symptoms of a unilateral upper motor neuron lesion (motor cortex or corticobulbar fibers) to CN V (trigeminal)?
The jaw jerk reflex may be increased
Would jaw weakness be expected with a unilateral upper motor neuron lesion to CN V?
No - there is bilateral input from upper motor neurons so weakness of jaw closing or opening would not be expected
What 3 symptoms would be expected with a unilateral lesion of CN V itself or it's nuclei?
1. Unilateral weakness of jaw closure
2. Reduced jaw jerk
3. Atrophy of the temporalis and masseter muscles
How can jaw strength be tested clinically?
Have pt bite down on a tongue depressor on both sides
What types of fibers does CN VII (facial) have?
Mixed - sensory and motor; also has a parasympathetic component
*sensory is covered on a separate lecture, so only motor and parasympathetic here
What is the motor nucleus of CN VII? Where is it located?
Facial nucleus - lies at the mid pons
What muscles do the motor fibers of VII innervate?
Muscles of facial expression (also stapedius)
Where does nervus intermedius synapse? What does it innervate?
Sphenopalatine and submandibular ganglia - to the lacrimal and salivary glands
Where do CN VII and nervus intermedius exit the brainstem?
At the pontomedullary junction (in a region called the cerebellopontine angle)
What do the axons leaving the facial nucleus pass over dorsal medially and loop over before exiting the brainstem?
The abducens nucleus
What is the bulge on the floor of the fourth ventricle created by facial nucleus axons called?
Via what foramen do facial nerve and nervus intermedius exit the calvarium?
Auditory canal (opening of the canal is the internal auditory meatus)
*facial nerve actually bends and exits ventrally out of the auditory canal via the stylomastoid foramen
How do you test the motor component of CN VII?
Ask patient to wrinkle their forehead, close eyes tightly, and show you their teeth - look for symmetry
What would be seen with a unilateral CN VII lesion of motor fibers?
Unilateral weakness of contralateral lower facial muscles but sparing of the forehead muscles
*this is because upper motor neuron innervation is bilateral to the forehead muscles but unilateral to the muscles of the lower face
*common cause is stroke
What symptoms would a unilateral lower motor neuron lesion of CN VII cause?
Ipsilateral weakness of the lower face and forehead muscles (hyperacusis (sensitivity to sound, due to weakness of stapedius muscle) and dry eye on ipsilateral side may also be present)
*common cause is Bell's palsy
What reflex do the motor fibers of CN VII mediate the efferent response of?
Corneal reflex (V1, ophthalmic n. mediates the afferent, via nasociliary nerve)
What is the parasympathetic nucleus of CN VII? Where is it located and what are the fibers leaving it called?
Superior salivatory nucleus - located near the midline of the upper medulla
* fibers leaving the nucleus = nervus intermedius
What kind of fibers does CN IX contain?
Mixed motor and sensory; also has parasympathetic fibers
What is the motor nucleus of CN IX? Location?
Nucleus ambiguus - located near the junction of pons and medulla (just caudal to pontomedullary junction)
((aMbiguus = motor; compare to nucleus Solitarius = sensory nucleus of 9 and 10))
What muscles does the motor component of CN IX innervate?
Stylopharyngeus (swallowing and palate elevation)
What is the parasympathetic nucleus of CN IX? Location? What are the fibers called when they leave the nucleus?
Inferior salivatory nucleus - near midline of the medulla
* axons leaving the nucleus are known as the lesser petrosal nerve