5.3 Trigeminal Neuroanatomy

Question 1

Where in the CNS is the mesencephalic nucleus?

Answer 1

midbrain

Question 2

Where in the CNS is the chief sensory nucleus?

Answer 2

pons

Question 3

Where in the CNS is the spinal trigeminal nucleus?

Answer 3

medulla

Question 4

What type of sensory modality does the chief sensory nucleus receive?

Answer 4

discriminative tactile and pressure input from the face and oral cavity

Question 5

What type of sensory modality does the spinal trigeminal nucleus receive?

Answer 5

Pain and temperature inputs from the face and oral cavity

Question 6

What type of sensory modality does the mesencephalic nucleus receive?

Answer 6

proprioceptive input from the head (muscles of mastication, teeth and hard palate, TMJ)

Question 7

What cranial nerves have 1st order sensory neurons that synapse in the spinal trigeminal nucleus?

Answer 7

CN V, VII, IX, X

Question 8

Which thalamic nucleus receives sensory info from the sensory trigeminal nuclei?

Answer 8

VPM nucleus of thalamus

Question 9

Axons from the Chief sensory nucleus ascend ipsilaterally as what tract?

Answer 9

dorsal trigeminothalamic tract

Question 10

Axons from the Spinal trigeminal nucleus cross and ascend as what tract?

Answer 10

ventral trigeminothalamic tract

Question 11

Where do the dorsal and ventral trigeminothalamic tracts project to/terminate?

Answer 11

3rd order VPM –> project to face area of post central gyrus

Question 12

Where is the trigeminal motor nucleus?

Answer 12

pons

Question 13

Are the cell bodies in the trigeminal motor nucleus upper or lower neurons?

Answer 13

lower neurons that innervate muscles of mastication

Question 14

What are the 2 sources of input that the trigeminal motor nucleus receives?

Answer 14

bilateral corticobulbar (upper motor neurons) and mesencephalic nucleus

Question 15

What is the afferent limb of the jaw jerk reflex?

Answer 15

sensory portion of V3

Question 16

What is the efferent limb of the jaw jerk reflex?

Answer 16

motor branch of V3

Question 17

If the jaw jerk reflex is present, what motor neurons were damaged in the trigeminal motor system?

Answer 17

corticobulbar pathways (upper motor neurons) –> trigeminal motor nucleus

Question 18

What is the efferent limb of the corneal reflex and where are its cell bodies?

Answer 18

CN VII cell bodies in facial motor nucleus

Question 19

What happens with the corneal reflex if there is a CN V1 lesion?

Answer 19

no direct or consensual reflex = can’t blink on either side

Question 20

What happens with the corneal reflex if there is a left CN VII lesion?

Answer 20

No direct = can’t blink left eye

intact consensual = right eye will blink

Question 21

What is the efferent limb of the lacrimal reflex and where are its cell bodies?

Answer 21

CN VII transmits impulses via superior salivatory nucleus

Question 22

What is the oculocardiac reflex?

Answer 22

bradycardia induced by compression of the eye ball

Question 23

What is the afferent pathway of the oculocardiac reflex?

Answer 23

CN V1

Question 24

What is the efferent pathway of the oculocardiac reflex?

Answer 24

dorsal motor nucleus of CN X (preganglionic parasympathetic fibers to cardiopulmonary plexus)