Flashcards in Trigeminal System - HY Deck (28):
What innervation does the trigeminal system provide?
1. Sensory innervation to the face, oral cavity, and supratentorial dura through general somatic afferent (GSA) fibers.
2. Also innervates the muscles of mastication through special visceral efferent (SVE) fibers.
What cells does the trigeminal ganglion contain?
Pseudounipolar ganglion cells.
How many divisions does the trigeminal ganglion have?
1. The ophthalmic nerve - V-1.
2. The maxillary - V-2.
3. The mandibular - V-3.
Discuss the anatomy of V1.
1. Lies in the wall of the cavernous sinus.
2. Enters the orbit through the superior orbital fissure.
3. Innervates the forehead + dorsum of the nose + upper eyelid + orbit (cornea + conjunctiva) + cranial dura.
4. Mediates the afferent limb of the corneal reflex.
Where does the V2 lie?
In the wall of the cavernous sinus.
What does the V2 innervate?
1. Upper lip and cheek.
2. Anterior portion of the temple.
3. Oral mucosa of the upper mouth.
7. Teeth and palate of the upper jaw.
8. Cranial dura
Through what foramen does V2 exit the skull?
Through the foramen rotundum.
Through what foramen does V3 exit the skull?
What sensory innervation does V3 provide?
1. Lower lip and chin
2. Posterior portion of the temple
3. External auditory meatus
4. Tympanic membrane
5. External ear
6. Teeth of the lower jaw
7. Oral mucosa of the cheeks and floor of the mouth
8. Anterior 2/3 of the tongue
9. Temporomandibular joint
10. Cranial dura
What division does the motor component (SVE) of V accompany?
The mandibular V3 through foramen ovale.
What does the motor component of the V innervate?
1. Muscles of mastication
3. Anterior belly of the digastric
4. Tensores tympani and veli palatini
5. Muscles that move the jaw
6. Lateral + medial pterygoids
What does the ventral trigeminothalamic tract mediate?
Pain + temperature sensation from the face and oral cavity.
Where are the 1st order neurons of the ventral trigeminothalamic tract?
1. Located in the trigeminal ganglion.
2. Give rise to axons that descend in the spinal tract of the trigeminal nerve.
3. Synapse with 2nd order neurons in the spinal nucleus of trigeminal nerve.
Where are the 2nd order neurons of the ventral trigeminothalamic tract?
1. Located in the spinal trigeminal nucleus.
2. Give rise to DECUSSATING axons that terminate in the CONTRALATERAL VPM nucleus of the thalamus.
Where are the 3rd order neurons of the ventral trigeminothalamic tract?
1. Located in the VPM nucleus of the thalamus.
2. Project through the posterior limb of the internal capsule to the face area of the somatosensory cortex (3, 1, 2).
What does the dorsal trigeminothalamic tract mediate?
Tactile discrimination and pressure sensation from the face and oral cavity.
Input from Meissner's and Pacinian corpuscles.
Where are the 1st order neurons of the dorsal spinothalamic tract located?
In the trigeminal ganglion.
Synapse in the principal sensory nucleus of CN V.
Where are the 2nd order neurons of the dorsal trigeminothalamic tract located?
1. In the principal sensory nucleus of CN V.
2. Project to IPSILATERAL VPM nucleus of the thalamus.
Where are the 3rd order neurons of the dorsal trigeminothalamic pathway located?
2. Project through the posterior limb of the internal capsule --> 3,1,2.
Mention the 4 main trigeminal reflexes.
1. Corneal reflex --> consensual disynaptic reflex.
2. Jaw jerk reflex --> monosynaptic myotactic reflex.
3. Tearing (lacrimal) reflex --> result of corneal or conjunctival irritation.
4. Oculocardiac reflex --> Pressure on the globe results in bradycardia.
Discuss the afferent/efferent limbs of the corneal reflex.
Afferent --> V1.
Efferent --> Facial nerve - VII.
Discuss the afferent/efferent limbs of the jaw jerk reflex.
Afferent --> V3 (cell bodies are found in the mesencephalic nucleus of CN V).
Efferent --> V3.
Discuss the afferent/efferent limbs of the tearing (lacrimal) reflex.
Afferent --> V1.
Efferent --> VII.
Discuss the afferent/efferent limbs of the oculocardiac reflex.
Afferent --> V1.
Efferent --> X.
What characterizes trigeminal neuralgia (tic douloureux)?
Recurrent paroxysms of sharp, stabbing pain in one or more branches of the trigeminal nerve on one side of the face.
What is the target group of trigeminal neuralgia?
Women over 50.
What is the drug of choice for idiopathic trigeminal neuralgia?