Trigeminal System

Question 1

What kind of information does the Trigeminal Nerve (CN V) primarily carry?

Answer 1

General Somatic Afferent (sensory) and Special Visceral Efferent (motor)

Question 2

Which CN V division is the only one that carries motor (General Efferent) fibers?

Answer 2

V3 (Mandibular division)

Question 3

Where does CN V emerge from the brainstem?

Answer 3

The Pons, at the level of the middle cerebellar peduncle

Question 4

What is the name of the ganglion where the cell bodies of most CN V sensory neurons are located?

Answer 4

Semilunar (Trigeminal/Gasserian) ganglion

Question 5

Which CN V division is purely sensory (General Afferent)?

Answer 5

V1 (Ophthalmic) and V2 (Maxillary)

Question 6

What skull opening does the Ophthalmic division (V1) pass through?

Answer 6

Superior orbital fissure

Question 7

What skull opening does the Maxillary division (V2) pass through?

Answer 7

Foramen rotundum

Question 8

What skull opening does the Mandibular division (V3) pass through?

Answer 8

Foramen ovale

Question 9

The distribution of V1, V2, and V3 on the skin of the face is an example of a what?

Answer 9

Dermatome (division of skin by peripheral nerves)

Question 10

Where are the cell bodies of the Lower Motor Neurons (LMNs) for CN V motor?

Answer 10

The Trigeminal motor nucleus (located in the pontine tegmentum)

Question 11

The UMNs (Upper Motor Neurons) that control the Trigeminal motor nucleus descend from where?

Answer 11

Primary motor cortex (head region) via the internal capsule

Question 12

What muscles are innervated by the V3 motor component?

Answer 12

Muscles of mastication (chewing muscles) and some suprahyoid muscles

Question 13

Where do the V3 motor axons exit the skull?

Answer 13

Foramen ovale (with the rest of V3)

Question 14

Which brainstem nucleus processes unconscious proprioception (stretch/pressure) for V1, V2, and V3?

Answer 14

Mesencephalic nucleus

Question 15

Where are the cell bodies for unconscious proprioception located in the Trigeminal system?

Answer 15

Mesencephalic trigeminal nucleus (not the semilunar ganglion)

Question 16

Which brainstem nucleus processes discriminative touch and conscious proprioception for V1, V2, and V3?

Answer 16

Pontine/Primary/Main sensory nucleus

Question 17

Which brainstem nucleus processes pain and temperature for CN V?

Answer 17

Spinal trigeminal nucleus

Question 18

The Spinal Trigeminal Nucleus extends from the Pons down to which spinal cord level?

Answer 18

C2

Question 19

What structures does the Mesencephalic nucleus receive unconscious proprioception from?

Answer 19

Masticatory muscles, extraocular muscles, and periodontal ligament

Question 20

In the Discriminative Touch Pathway, axons from the oral cavity travel via which tract?

Answer 20

Dorsal Trigeminothalamic tract (terminates in ipsilateral thalamus)

Question 21

In the Discriminative Touch Pathway, other axons leave the primary nucleus, decussate, and travel via which tract?

Answer 21

Ventral Trigeminothalamic tract (terminates in contralateral thalamus)

Question 22

In the Trigeminal Pain & Temperature pathway, the 1st order neurons descend to form which tract?

Answer 22

Spinal trigeminal tract (extends from pons to C2)

Question 23

What is the Trigeminal Lemniscus composed of?

Answer 23

Decussated 2nd order fibers carrying pain/temp (from spinal nucleus) and decussated/uncrossed fine touch fibers (from main sensory nucleus)

Question 24

Which CN V nucleus is the afferent (sensory) pathway for the Jaw-Jerk Reflex?

Answer 24

Mesencephalic trigeminal nucleus (V3)

Question 25

Which CN V division is the afferent (sensory) pathway for the Corneal Reflex?

Answer 25

V1 (Ophthalmic division via the nasociliary nerve)

Question 26

Which CN carries the efferent (motor) signal that closes the eye during the Corneal Reflex?

Answer 26

CN VII (Facial Nerve, motor nucleus)

Question 27

The "onion-skin" pattern of sensory loss on the face is caused by what?

Answer 27

The rostral-to-caudal somatotopy of the face within the spinal nucleus of CN V

Question 28

In the spinal nucleus somatotopy, which facial areas are represented more cranially (rostrally)?

Answer 28

Areas closer to the mouth