Anatomy - Main Sensory Nucleus (Trigeminal)

Question 1

what is the main sensory nucleus (msT) sensitive to

Answer 1

touch and pressure

Question 2

what is the mesencephalic nucleus (mes) sensitive to

Answer 2

proprioceptive affarents from TMJ and masticatory muscles

how to chew, when to chew, etc

Question 3

describe the location of the mesencephalic nucleus, chief sensory nucleus, trigeminal ganglion, and spinal nucleus of trigeminal

Answer 3

mesencephalic: in the midbrain, most rostral
chief sensory: below mesencephalic
trigeminal ganglion: outside the CNS (DRG)
spinal: extends down spinal cord to upper cervical spine

Question 4

function of main sensory nucleus

Answer 4

process proprioceptive information for head and face

Question 5

compare the dorsomedial and ventrolateral divisions of the main sensory nucleus

Answer 5

dorsomedial: gets afferent input from oral cavity
ventrolateral: gets afferents from branches V1, V2, and V3

Question 6

where are the second order neurons in the trigeminal sensory tract

Answer 6

in the principal sensory nculeus

Question 7

describe the somatotopic representation of the main sensory nucleus

Answer 7

V1 is located most anterior
V2 in the middle
V3 is most posterior

Question 8

what happens to neurons synapsing in the dorsomedial division of the main sensory nucleus

Answer 8

they travel ipsilaterally via posterior trigeminothalamic tract

Question 9

what happens to neurons synapsing in the ventrolateral division of the main sensory nucleus

Answer 9

they travel contralaterally via anterior trigeminothalamic tract

Question 10

where do neurons from the anterior and posterior trigeminothalamic tracts synapse

Answer 10

the ventro posteromedial nucleus (VPM)

Question 11

neurons synapsed in VPM then travel where

Answer 11

through posterior limb of internal capsule and to the primary somatosensory cortex

Question 12

name the nuclei for each:

• proprioception to lower extremity
• proprioception to upper extremity
• proprioception to face

Answer 12

LE: gracile nucleus
UE: cuneate nucleus
face: main sensory nucleus (trigeminal)

Question 13

what is the mesencephalic nucleus comprised of and where is it found

Answer 13

comprised of pseudounipolar neurons

- found in the CNS (embedded in the brainstem)

Question 14

where do neurons from the mesencephalic nucleus project to

Answer 14

to the main sensory nucleus and spinal nucleus

some terminate in trigeminal motor nucleus to do jaw jerk reflex

Question 15

-motor flashcard-

how does UMN lesion affect the jaw jerk reflex?

Answer 15

it enhances it

Question 16

what is the jaw jerk reflex

Answer 16

applying a downward tap on the chin which stretches the masseter and causes it to contract bilaterally

Question 17

what makes up the afferent and efferent limbs of the jaw jerk reflex

Answer 17

afferent: peripheral processes from mesencephalic trigeminal neuron
efferent: central processes from mesencephalic trigeminal neuron that synapse on a trigeminal motor neuron

Question 18

where do neurons from the mesencephalic nucleus and main sensory nucleus travel to relay proprioceptive information from the face to the cerebellum

Answer 18

neurons travel through the cerebellar peduncle

Question 19

what nucleus sends the majority of neurons to the cerebellum to relay proprioceptive information from the face

Answer 19

mesencephalic

main sensory nucleus is minor