Cranial Nerves V & VII Flashcards
What are three divisions of Trigeminal Nerve?
Ophthalmic (V1) - Upper face - Sensory only Maxillary (V2) - Middle face - Sensory only Mandibular (V3) - Lower face - Sensory and Motor
Trigeminal mesencephalic nucleus is located where?
Midbrain
Trigeminal principal Nucleus is located where?
Pons
Trigeminal spinal nucleus is located where?
Medulla
Trigeminal motor nucleus is located in the….
Pons
What projections do you find off of the Trigeminal spinal nucleus?
Contralateral projection to Ventral posteromedial nucleus of thalamus.
(Internal capsule, postcentral parietal lobe.)
Main trigeminal sensory nucleus gives of what projections?
Bilateral projection to ventral posteromedial nucleus of thalamus. (internal capsule, postcentral gyrus parietal lobe)
Where are the cell bodies of the trigeminal nerve found?
In the trigeminal ganglion
Function of Pars Oralis….
Receives input from intraoral and premolar structures.
Function of Pars interpolaris proper….
Activation of trigemini-autonomic reflexes.
3 key features of the Caudalis-Interpolaris transitional zone…
- Not somatotopically organized.
- Responds to pain stimuli from many areas served by V
- May be involved in activation of pain suppression mechanisms
What is the target of fibers that mediate Pain, crude touch, and Temperature sensation?
Pars Caudalis
- Superficial structures include oral cavity & teeth
- Deep structures include jaw muscles and TMJ
Describe structure of Pars Caudalis…
- Laminar structure
- Blends with posterior horn of cervical cord.
- Somatotopic organization
______ descends thru the spinal trigeminal tract and synapse in the ________.
Afferents, caudal nucleus
What is the organization of pain-temperature afferents in the Pars caudalis?
Mandibular division = Dorsal
Ophthalmic = Ventral
Maxillary = In between
Fibers representing back of the face end in the ______.
Upper cervical cord
Fibers representing the center of the face end near the _____.
Obex
The more _______ the spinal injury is, the larger the area around the mouth that is spared of sensory loss.
Caudal
What can you tell me about nerve fibers in the tooth pulp?
- 70-80% of fibers are A-delta (fast pain, thermal) and C (Slow pain, itch, touch)
- 20-30% of fibers are A-beta (Spindle, touch & pressure)
- Fibers project to Trigeminal main sensory nucleus, Trigeminal spinal nucleus & Upper cervical spinal cord.
What is Trigeminal Nueralgia?
- Brief episodes of excruciating pain in distributation of one (or more) division of the trigeminal nerve.
(70% = mandibular divison) - No sensory trouble between attacks.
- Often tactile stimulus triggers attacks
- A number of cases due to trigeminal compression by vessel or tumor. (Most are caused by Superior cerebellar artery)
- surgical solutions include cutting nerve root, inducing lesion in trigeminal ganglion. *Result is loss of ALL tactile sensation to the area.
- Or section spinal trigeminal tract slightly caudal to obex…tactile sensation is intact but pain is gone…….Compromises medullary cardiovascular & respiratory centers though.
What are the major nerve connections of the Tirgeminal nerve? (4)
- Peripheral branches of mesencephalic neuron innervated the masseter
- Tactile Efferents
- Motor neuron fibers: muscles of mass.
- Pain-tempature afferents
Tell me about the Jaw-jerk reflex….
- monosynaptic reflex
- Downward tap on chin
- Like other reflexes it is enhanced with UMN damage, (In fact it used to determine level of injury)
- Efferent limb: V motor nucleus
- Afferent limb: mesencephalic V neuron innervating masseter spindle.
What does the Trigeminal Motor nucleus do?
- Innervates “MOM & the Tensor twins”
- Branchial motor nucleus (Ist arch muscles)
- Efferent Limb of Jaw jerk
Where is the Supratrigeminal nucleus and what does it do?
- It is located just superior to the Trigeminal motor nucleus, in the pons.
- Actually part of reticular formation
- **Pattern generator for masticatory rhythm
Trigeminal Motor nucleus: Function, Termination & Lesion effects…
Function = Jaw closure
Terminates in = Muscles of Mastication
Lesion = Jaw closure is weakened & opened jaw will deviate toward side of lesion.
Describe Mesencephalic nucleus….
- Heavily myelinated fibers
- Posterior column homologue (medial lemniscal system)
- proprioception
Describe Main sensory nucleus….
- Heavily myelinated fibers
- Posterior column homologue (medial lemniscal system)
- Discriminative touch
Describe Spinal Nucleus….
- Lightly myelinated fibers
- Homologue of anterolateral system
- Pain, crude touch, temperature
