Exam #2: Cranial Nerves III Flashcards
Generally, what are the two functions of CN V?
1) Sensory innervation of the face
2) Motor innervation to the muscles of mastication
What are the functional components of the Trigeminal Nerve?
1) GSA= touch, pressure, pain, temp
2) GP
3) SVE
What is special about the motor innervation of CN V?
1st CN to provide “branchioMOTOR” innervation i.e. innervation to muscles derived from the pharyngeal arches
List the muscles of mastication.
Temproalis
Masseter
Medial pterygoid
Lateral pterygoid
In addition to the muscles of mastication, what other muscles does the Trigeminal Nerve innervate?
Mylohyoid
Digastric*
Tensor Tympani
Tensor veli palatini
*Only the anterior belly
What is unique about the trigemintal nerve?
It is the only CN to carry PNS “hitch-hikers”
What are the four PNS hitch-hikers that the trigeminal nerve carries?
1) Ciliary ganglion
2) Pterygopalatine ganglion
3) Submandibular ganglion
4) Otic ganglion
What ganglion is associated with V1? What nerve are the pre-synaptic fibers of this ganglion from? Where are they going?
- Ciliary ganglion
- Oculomotor nerve
- PNS to Sphincter pupillae & ciliary m.
What ganglion is associated with V2? What nerve are the pre-synaptic fibers of this ganglion from?
- Pterygopalatine ganglion
- Facial nerve
- PNS to Lacrimal, nasal, and palatine glands
What ganglia are associated with V3? What nerves are the pre-synaptic fibers of these ganglia from?
- Submandibular ganglion
- Facial nerve
- PNS to Sublingual & submandibular glands
- Otic ganglion
- Glossopharyngeal nerve
- PNS to Parotid gland
What is the SNS hitch-hiker carried by the trigeminal nerve?
SNS innervation to the dilator pupillae m. is carried by V1
Which branch of CN V has BOTH motor and sensory innervation?
V.3 (mandibular)
V.1 & V.2 are SENOSRY only
Where does the trigeminal nerve emerge?
Lateral pons
What is the swelling of the trigeminal nerve?
Trigeminal ganglion i.e. a DRG of the head
Looking from a dorsal view of the skull, list the branches of the trigeminal nerve from medial to lateral.
Ophthalmic, maxillary, & mandibular
What sinus does the trigeminal nerve traverse?
Cavernous
What foramen does the Ophthalmic division of CN V exit?
Superior orbital fissure
What foramen does the Maxillary division of CN V exit?
Rotundum
What foramen does the Mandibular division of CN V exit?
Ovale
What are the four nuclei associated with the trigeminal nerve?
1) Motor nucleus
2) Mesencephalic nucleus
3) Main/ Principal Sensory nucleus
4) Spinal nucleus
What is the function of the motor nucleus of the trigeminal nerve?
Cell bodies of LMN that form the motor root of V.3 to innervate the muscles of mastication
What is the function of the mesencephalic nucleus of the trigeminal nerve?
General proprioception (muscles of mastication)
*Contains the cell bodies of PSEUDOUNIPOLAR neurons
What is the function of the main/principal sensory nucleus of the trigeminal nerve?
- Discriminative touch
- Sensation from the face
- Proprioception of the EOM & TMJ
What is the function of the spinal nucleus of the trigeminal nerve?
Nociception
Temperature
What is the only nerve to have a pain nucleus?
Trigeminal nucleus
What other nerves send pain fibers of the spinal nucleus of the trigeminal nerve?
VII
IX
X
What are the four tracts of the trigemninal nerve?
1) Spinal tract of trigeminal
2) Ventral trigeminal lemniscus
3) Dorsal trigeminal lemniscus
4) Trigeminoreticular fibers
What is the spinal tract of the trigeminal nerve?
This is an s sensory tract that merges with Lissauer’s Tract in the upper cervical spinal cord
- Paradoxically, axons descend from the pons to medulla or C1/C2 to terminate in the spinal nucleus of trigeminal
What is the function of the spinal tract of the trigeminal nerve?
- Pain
- Temperature
- Tactile sensation
What is the ventral trigeminal lemniscus?
This is the tract that ascends from the spinal nucleus of the trigeminal to the VPM nucleus of the thalamus
What is the function of the trigeminal lemniscus?
- Pain
- Temperature
- Tactile sensation
What is the ventral trigeminal lemniscus similar to?
Spinothalamic tract of the anterolateral system
What is the dorsal trigeminal lemniscus?
This is the tract from the main sensory nucleus of V to the VPM nucleus of the thalamus
What is the function of the dorsal trigeminal lemniscus?
- Fine discriminative touch
- Proprioception
What is the dorsal trigeminal lemniscus similar to?
DC/ML pathway
Where does the VPM nucleus of the thalamus project?
Postcentral gyrus
Outline the pathway for DISCRIMINATORY TOUCH & PRESSURE sensation from the orofacial region.
1) 1st order= trigeminal ganglion
2) 2nd order= main sensory nucleus of V
3) Axons join DORSAL TRIGEMINAL LEMNISCUS
4) VPM of the thalamus
5) Postcentral Gyrus
Outline the pathway for PAIN & TEMPERATURE sensation from the orofacial region.
1) 1st order= Trigeminal ganglion
2) Axons descend the spinal tract of V to spinal nucleus
3) 2nd order= spinal nucleus of V
4) Axons join the VENTRAL TRIGEMINAL LEMNISCUS
5) 3rd order= VMP of thalamus
- And cingulate/ insular cortices (emotional component of pain)
6) Postcentral gyrus
Outline the GENERAL PROPRIOCEPTION PATHWAY of the trigeminal nerve.
1st order= mesencephalic nucleus
Central processes=
1) Main sensory nucleus of V
2) Motor nucleus of V
**This arrangement results in REFLEX movement of the jaw
What is the role of the trigeminal nerve in the corneal blink reflex?
Afferent limb
What happens if there is damage to V.1 (Ophthalmic division)?
- Reduced sensation to V.1 zone (upper 1/3)
- Inhibits corneal blink reflex
What happens if there is damage to V.2 (Maxillary division)?
Reduced or inhibited sensation to V.2 zone
What happens if there is damage to V.3 (Mandibular division)?
- Reduced or inhibited sensation to V.3 zone
- Paralysis to muscles of mastication
*****Jaw will deviate TO side of LESION
What is trigeminal neuralgia?
Sharp, intermittent, excruciating pain to one side of the face that is caused by:
1) Demyelination of CN V
2) Vascular formations that impinge on CN V (resulting in demyelination) –specifically, SUPERIOR CEREBELLAR ARTERY
Why does demyelination of CN V result in pain?
Ephatic transmission of nerve impulses i.e. “short-circuiting” & cross talk
What is the result of a lesion to the spinal tract of V?
Loss of pain & temperature sensation from the IPSILATERAL side of the face
- Diminution of tactile sense (main sensory is still intact)
What is the result of a lesion to the ventral V lemniscus?
Loss of pain & temperature sensation from the CONTRALATERAL side of the face
- Diminution of tactile sense (main sensory is still intact)
What is the result of a lesion to the dorsal V lemniscus?
Diminution of tactile sense from the IPSILATERAL side of the face
