Lecture 10: Midbrain and Cranial Pons

Question 1

Which nerve(s) does the trochlear serve? What types of fibers?

Answer 1

cranial nerve IV, somatomotor fibers serving striated muscle (superior oblique)

Question 2

What is unique about the trochlear nerve?

Answer 2

it exits dorsally

Question 3

Describe the path of the trochlear nucleus? (midbrain)

Answer 3

just ventral and medial to the periaqueductal gray and ventures around the aqueduct dorsally and crosses superior and oblique

Question 4

Name the nuclei of the trigeminal complex (4)

Answer 4

trigeminal motor nucleus, mesencephalic V, chief sensory trigeminal and the spinal trigeminal (stretch along whole length of the brainstem)

Question 5

What types of fibers are in the trigeminal motor nucleus?

Answer 5

branchial motor (located more laterally) that supply striated muscle, muscles of mastication and tensor tympani

Question 6

What types of fibers are found in the mesencephalic V? (midbrain)

Answer 6

(pseudo DR ganglion) somatosensory carrying unconscious proprioception of the jaw

Question 7

What types of fibers are found in the chief sensory trigeminal? (where? seriously I have no idea)

Answer 7

somatosensory carrying touch sensation for the head and face

Question 8

What types of fibers are found in the spinal trigeminal? (extends from the pons down to the cervical spinal cord)

Answer 8

somatosensory: pain and temp to the face and head

Question 9

Discuss the path of alpha-beta, C/delta fibers and Ia,Ib and II and alpha motor neurons

Answer 9

alpha beta come in and synapse on the chief nucleus, cross the midline and ascend to the thalamus in the TTT (trigeminal thalamus tract) to the VPM; c, delta fibers come in and descend to the spinal nucleus, cross the midline and ascend to the thalamus; Ia,Ib and II come in and synapse on the mesencephalic nucleus before giving input to the motor nucleus V; motor nucleus V sends information via alpha motor neurons to the muscles of mastication

Question 10

A lesion in the motor V might lead to what types of symptoms?

Answer 10

weakness in opening and closing the mouth, jaw deviates to the weak side and hyperacusis (acoustic)

Question 11

CNV innervates tensor tympani for what purpose?

Answer 11

to dampens sounds (ie. from chewing)

Question 12

Describe the jaw jerk reflex?

Answer 12

reflex loop created by the fibers synapsing on the mesencephalic nucleus V that feedback onto the motor nucleus that cause the movement of the muscles of mastication (reflexes increases with UMN lesion)

Question 13

Where are motor nuclei located (generally) in relationship to the sensory nuclei?

Answer 13

from medial to lateral: somatomotor, branchiomotor, visceromotor, visceral sensory, somatosensory and special sensory

Question 14

Describe the two nuclei of the oculomotor complex (in the upper midbrain).

Answer 14

serves cranial nerve III: oculomotor nucleus and the Edinger-Westphal nucleus

Question 15

What type of fibers does the oculomotor nucleus serve?

Answer 15

somatomotor to the eye muscles traveling via the oculomotor nucleus

Question 16

What type of fibers does the Edinger-Westphal nucleus serve?

Answer 16

autonomic- preganglionic parasympathetic to the iris and the cilia muscles (lens focus) which travel via the oculomotor

Question 17

Where are the oculomotor nerves located relatively?

Answer 17

ventral to the brainstem, rostral to the pons near the midline: the tract travels ipsilaterally and ventrally from the nuclei until it exits the brainstem

Question 18

What are symptoms of CNIII palsy?

Answer 18

closed lid (lavator palpebrae), deviated eye (diplopia-double vision) and dilated pupil (autonomics)

Question 19

What is the medial longitudinal fascicles?

Answer 19

tract of vestibular and motor neurons for eye movement (? not positive on this)

Question 20

How are the fibers of the spinal nucleus organized?

Answer 20

more caudal is represents the top/back of the head whereas the mouth/jaw is represented cranially; fibers from different cranial fibers enter along the descending pathways of the spinal nucleus; also more caudal signal is more localized pain

Question 21

Describe the type of fibers in the abducens nucleus?

Answer 21

somatic motor that serves the extrinsic eye muscles via the abducens nerve (VI) as well as interneurons that help to coordinate eye movements (this tract crosses the midline)

Question 22

What is significant about the tracts of the abducens

Answer 22

one tract says ipsilateral and one goes contralateral which is uniquely suited to control two different eyes to focus on a stimulus (coordinated eye movements)

Question 23

What types of fibers does the cerebral peduncle contain?

Answer 23

Fibers traveling down from the cerebrum: corticopontine, coricospinal and corticobulbar

Question 24

Describe the type of fibers from the facial nucleus and what they innervate. (caudal pons) AKA motor nucleus VII

Answer 24

branchial motor to striated muscle for facial expression

Question 25

Describe the type of fibers from the superior salivary nucleus and what they innervate.

Answer 25

visceromotor (autonomic) to the submandibular, sublingual and lacrimal glands

Question 26

Describe the fibers coming from the spinal nucleus V and what they innervate.

Answer 26

somatosensory of pain/temperature from the ear, and face

Question 27

Describe the fibers coming from the nucleus of the solitary tract and what they innervate.

Answer 27

visceral sensory: taste to the anterior ⅔ parts of the tongue

Question 28

Name the types of fibers that CN VII carries (4) and where they go.

Answer 28

the facial nerve contains branchio motor to LMN in the face and middle ear (motor root), pregangionics to the superior salivary and lacrimal glands (intermediate root) and visceral-tatse to anterior ⅔ tongue and somatosensory pain/temp- ear (sensory geniculate ganglion)

Question 29

Describe the path of the facial nucleus (motor VII)

Answer 29

motor nucleus of VII sits just lateral and anterior to the superior olive in the caudal pons and heads medially and anteriorly to wrap around the nucleus of the abducens and heads out of the lateral brainstem

Question 30

Describe the symptoms of a VII lesion

Answer 30

ispislateral symptoms including: face sags (muscles of facial expression), cannont close eye (obicularis oculi) and hyperacusis (stapedius)

Question 31

Corticobulbars carry cortical input to facial nucleus and synapse on the upper and lower motor VII nuclei, what are the symptoms of a lesion of either

Answer 31

the top receives synapse unilaterally, so a lesion to one side is unlikely to cause problems but the lower nucleus receives synapse only from the contralateral side and if this is damaged, it can lead to lower face problems without affect of the upper face

Question 32

Dampening of the stapedius is controlled by what nerve?

Answer 32

VII (facial)