Corticobulbar Pathway Flashcards
what is the pathway of the corticobulbar tract?
pre-central gyrus motor cortex —–> corona radiata —–> genu of internal capsule ——> crus cerebri —–> correct cranial nerve nuclei
Cranial nerve V3 has motor innervation to what muscles?
- muscles of mastication (temporalis, masseter, med and lateral pterygoids)
- tensor tympani
- tensor veli palatini
- mylohyoid
- anterior belly of digastric
where does a motor signal originate if you clench your jaw or smile? what is the blood supply to this region?
- inferior lateral region of the precentral gyrus
- middle cerebral artery
what is the CN V motor pathway?
UMN: motor cortex —–> internal capsule —–> crus cerebri —-> terminates bilaterally at CN V nuclei in the pons
LMN: motor nuclei of CN V —–> trigeminal ganglion —-> V3 —-> muscle
what are the sensory modalities of CN V?
- proprioception
- touch
- pressure
- vibration
- pain
- temperature
what is the sensory nuclei for proprioception and where is it located?
- mesencephalic nucleus
- midbrain
what is the sensory nuclei for touch, pressure and vibration and where is it located?
- main sensory nucleus
- pons
what is the sensory nuclei for pain and temperature and where is it located?
- spinal nucleus
- pons, medulla and spinal cord
**very long nucleus
what is the basic CN V sensory pathway?
sensory receptors ——> trigeminal ganglion (1st order) —–> mesencephalic/main/spinal nucleus (2nd order) ——> decussation —–> VPM nucleus of thalamus (3rd order) ——> internal capsule ——> post central gyrus
what is the CN V sensory pathway for touch, pressure and vibration?
1st order neuron
- trigeminal ganglion cells
2nd order neuron
- synapse in principal main nucleus (pons)
- fibers cross midline
- trigeminothalmic tract ( trigeminal lemiscus) ascends
3rd order neuron:
- synapse in the VPM of the thalamus
- axons enter internal capsule
- primary somatosensory cortex (post central gyrus)
what is the CN V sensory pathway for pain and temperature?
1st order neuron
- trigeminal ganglion cells enter at pons
- fibers descend in the spinal trigeminal tract
2nd order neuron
- synapse at the spinal nucleus in the medulla
- fibers cross midline
- trigeminothalamic tract (trigeminal lemiscus) ascends
3rd order neuron
- synapse at the VPM of the thalamus
- axons enter internal capsule
- primary somatosensory cortex (post central gyrus
what is the trigeminal pathway for proprioception?
- originates in the muscles of mastication and periodontal ligaments
- the sensory and motor feedback controls bite force
- both motor and sensory cell bodies are in the CNS
- motor nuclei of V (efferent) and mesencephalic nuclei for sensory (afferent)
what would be the result of an upper motor neuron lesion and a lower motor neuron lesion to the proprioception pathway of CN V?
- UMN: hyperactive/ repeating reflex
- LMN: reflex is absent
what are the efferent and afferent limbs of the corneal blink reflex?
touch or irritation to the cornea causes
- afferent limb: ophthalamic division of V for sensory information
- efferent limb: facial nerve motor for muscle that closes the eye (obicularus oculi)
what is the shingles virus mode of action?
- virus within the dorsal root trigeminal ganglion
- unilateral (in ganglion not nucleus)
- hitches a ride with the nerve that innervates a certain dermatome
what is trigeminal neuralgia?
chronic pain condition involving the trigeminal nerve of the face
**considered secondary neuralgia if caused by a tumor or MS
what is the path of the facial nerve in order to innervate the muscles of facial expression?
ponto-medullary junction then exits at internal acoustic meatus then goes through the facial canal and exits at the stylomastoid foramen
what facial muscles are innervated by the facial nerve?
- buccinator
- platysma
- orbicularis oculi
- zygomaticus major
- levator labii superiorus
- orbicularis oris
- mentalis
- depressor anguli oris
what is the cranial nerve VII motor pathway?
UMN: precentral gyrus motor cortex —-> corona radiata —–> crus cerebri —–> terminates in the pons at facial nucleus
LMN: facial nucleus —–> muscles of facial expression
what would happen with an UMN lesion and a LMN lesion of the facial nerve and why?
UMN: lack of movement only to the LOWER face due to the lower face only having contralateral projections and upper face having bilateral projections (supranuclear lesion)
LMN: would cause both upper and lower face to lack motor innervation (bells palsy; facial nerve lesion)
what is the cranial nerve XII motor pathway?
UMN: motor cortex pre central gyrus —–> corona radiata —–> internal capsule ——> crus cerebri —–> terminates at medulla
LMN: synapse in contralateral hypoglossal nucleus
what muscles does the hypoglossal XII nerve innervate?
genioglossus
hyoglossus
styloglossus
the hypoglossal nerve comes out of what cranial opening?
hypoglossal canal
what would happen with a LMN and UMN lesion of CN XII?
UMN: corticobulbar tract to the hypoglossal nucleus decussates before synapsing
** lesion would cause CONTRALATERAL tongue deviation
LMN: region below the nucleus innervates IPSILATERALLY
** lesion would cause same side tongue deviation
