CN V and VII Flashcards
What does CN V transmit?
tactile, proprioceptive, pain, temp from head to cortex
3 divisions of CN V
ophthalmic (V1) -> upper face, sensory only
maxillary (V2) -> middle face, sensory
Mandibular (V3) -> Lower face, sensory and motor
CN V fiber types
mesencephalic nucleus of trigeminal tract, trigeminal main sensory nucleus and trigeminal motor nucleus
Where happens if there is a lesion in motor components of CN V?
jaw closure weakened, opened jaw will deviate toward side of lesion
Where do cell bodies of CN V motor nucleus terminate?
mm of mastication
Which CN V nucleus is part of reticular formation?
supratrige minal nucleus
What is the supratrige minal nucleus a pattern generator for?
masticatory rhythm
Where does the centrally directed process of mesencephalic nucleus of CN V (sensory afferent) terminate?
trigeminal motor nucleus (jaw jerk reflex) and supratrigeminal nucleus (chewing movements)
What does mesencephalic nucleus of CN V sense?
proprioception, spindles in mm of mastication, mechanoreceptors in gums, teeth and hard palate
What are the proprioception receptors of the mesencephalic nucleus?
- neuromuscular spindles of mastication mm
- pressure/tension receptors in periodontal ligaments
What does proprioception part of mesencephalic nucleus control?
distance between mandible and maxilla (occlusal vertical dimension)
Which brodmann’s areas are the cortical representation of CN V?
3, 1, 2
What does the main sensory nucleus of CN V serve?
face, head, oral cavity, teeth, meninges
Where does the main sensory nucleus of CN V terminate?
main/principal trigeminal sensory nucleus - discriminative touch and vibration
What is the main sensory nucleus of CN V a homologue of?
posterior column nuclei
What are the two ascending pathways of main sensory nucleus of CN V?
crossed pathway that joins DCML on way to VPM and uncrosses (dorsal trigeminal tract) inside of mouth represented to VPM
What does the spinal trigeminal nucleus of CN V serve?
face, oral cavity, teeth and meninges
Where does the spinal trigeminal nucleus terminate?
trigeminal spinal nucleus - pain, crude touch and temp
Where are the cell bodies of spinal trigemnical nucleus of CN V?
trigeminal ganglion
Where do afferent descend of the spinal trigeminal tract?
thru spinal trigmenial tract and synapse in caudal nucleus
- second order neurons send axons across midline that ascend and join STT, terminate in VPM
Which sensory systems of CN V are myelinated?
mesencephalic nucleus and main sensory nucleus are heavily myelinated while the spinal nucleus is lightly myelinated
What is the homologue of the spinal nucleus?
STT
Which ascending CN V projections are bilateral and contralateral?
spinal nucleus = contralateral projection
main trigeminal sensory nucleus = bilateral
What does the pars caudal blend with?
posterior horn of cervical cord
3 parts of spinal trigeminal nucleus
pars oralis, pars interpolaris, pars caudalis
What is the somatotopic organization of pars caudal?
inverted representation of face; onion peel
- primarily pain fibers
What does substantial gelatinous contain?
excitatory and inhibitory interneurons
- receives raphe spinal tract fibers (serotonin)
Where do afferent fibers come from to the pars caudalis?
CN VII, IX, X - for area near ear
Arrangement of pain and temp afferents in spinal trigeminal nucleus
mand = dorsal ophthalmic = ventral maxillary = between fibers from center face end near obex fibers from back of face end in upper cervical cord
Where are dried episodes of pain in distribution of one division of CN V originate from?
mand division = 70%
ophthalmic = <5%
Treatment of trigemnial neuralgia. Result?
cutting nerve root, introducing lesion in trigeminal ganglion
Result = loss of all tactile sensation
What occurs when afferents are removed to the caudal nucleus?
tactile sensation is intact but pain sensation to over half of face is lost
Which artery is most frequently involved in trigeminal neuralgia due to vascular cause?
branches of superior cerebellar a
Where does CN VII provide motor innervation?
mm of facial expression, stapedius m
Where does CN VII provide sensory innervation?
skin of outer ear (geniculate ganglion), palatine tonsil and posterior nasal cavity
What are the actions of CN VII other than sensory and motor?
taste, salivation, lacrimation (lubricates cornea)
Where do fibers from CN VII enter for the skin and outer ear?
spinal trigeminal tract and act exactly as trigeminal afferents
Which motor neurons of CN VII innervate contra laterally and bilaterally?
lower face mm = contralateral cortex
upper face mm = bilaterally
What does unilateral damage to corticobulbar pathway result in?
inability to smile or bare teeth symmetrically but ability to wrinkle forehead is unaffected
Bell’s palsy symptoms
paresis of facial mm, irritation of cornea, hyperacusis (stapedius), reduced lacrimation and salivation
Where does the afferent limb go in the corneal blink reflex? efferent limb?
- V1 to spinal V tracy
- VII elicited by bilateral projection from spinal V nuclues/RF
What type of felafel is the jaw jerk?
monosynaptic reflex
Where do the afferent limbs extend in the jaw jerk reflex? Efferent limb?
- mesencephalic V neuron innervating masseter spindle
- V motor neuron
What do olfactory receptors of the tongue respond to?
food vapors
What is flavor of the tongue due to?
chemosensitive and somatosensory free n endings of V (IX and X) in mucus membranes of oral cavity
What accounts for the large variations in taste among people?
number of papillae and taste buds and amount of taste buds in fungiform papillae
What afferents reach the nucleus in taste pathways vis solitary tract?
gustatory afferents
What do second order fibers of taste pathways do?
- reflex activities (swallowing and salivation)
- project uncrossed to thalamus (VPM), then to gustatory cortex (insula, medial surface or frontal operculum)
Where does gustatory cortex project?
orbitofrontal cortex -> integrated with olfactory info -> amygdala -> limbic system and hypothatlamus
