06b: Central Vestibular System

Question 1

Vestibular, aka (X), ganglion sends axons into CNS that courses medial to (Y) structure(s).

Answer 1

X = Scarpa's
Y = cochlear nuclei and ICP

Question 2

Vestibular axons enter CNS and terminate in which subdivisions of vestibular nucleus?

Answer 2

All 4 major subdivisions

Question 3

List the subdivisions of vestibular nucleus, named based on their location wrt (X).

Answer 3

X = cerebellum;

Inferior, superior, medial, lateral

Question 4

A lesion affecting (X) surface of (Y) brainstem structures is likely to impact vestibular system.

Answer 4

X = dorsal;

Y = medulla and pons

Question 5

Through (X), a subdivision of (Y), the vestibular ganglion, unlike any other sensory system, sends axonal projections directly to (Z).

Answer 5

X = juxtarestiform body;
Y = ICP
Z = vestibular cerebellum

Question 6

The vestibular cerebellum is composed of which region(s)?

Answer 6

Flocculo-nodular lobe

Question 7

Main central projections from vestibular nuclei are to (X).

Answer 7

X = SC, cerebellum, oculomotor nuclei

Question 8

T/F: Some neurons in vestibular nuclei also send axons to thalamus.

Answer 8

True

Question 9

Deiter’s nucleus, aka (X), projects to (Y) via (Z) tract.

Answer 9

X = lateral vestibular nucleus;
Y = interneurons/motor neurons along entire length of SC (antigravity muscles)
Z = lateral vestibulospinal tract

Question 10

Head and trunk tilt to the right. Which side of vestibular system activated?

Answer 10

Right

Question 11

Head and trunk tilt to the right. Which lower-extremity muscles activated on R/L sides by (X) tract?

Answer 11

R: Extensors
L: Flexors

X = lateral vestibulo-spinal

Question 12

Patient walks in with stumbling/falling to L side. You realize it’s due to inability to contract L lower extensors in response to body tilt. Which tract has been (ipsi/contra/bi)-laterally impaired?

Answer 12

Ipsilateral Lateral vestibulospinal tract

Question 13

Vestibulospinal reflexes are coordinated with (X) reflexes. What does each respond to?

Answer 13

X = cervicospinal

VS: responds to head tilt
CS: responds to trunk tilt

Question 14

Vestibular nuclei and (X) tract receive strong (stimulatory/inhibitory) influences from higher brain centers.

Answer 14

X = lateral vestibulospinal tract;

Inhibitory

Question 15

Decerebrate rigidity is characterized by (X) symptoms. Where’s the lesion?

Answer 15

X = involuntary overactivity of extensor muscles, including upper body;

BELOW red nucleus, impairing higher brain centers that normally indirectly inhibit extensor muscle tone

Question 16

Medial vestibular nucleus projects (up/down) to:

Answer 16

Up: extraocular motorneurons
Down: neck motorneurons

Question 17

Medial vestibulospinal tract, aka (X), projects (ipsi/contra/bi)-laterally to which part(s) of SC?

Answer 17

X = descending MLF
Bilaterally;

Cervical segments

Question 18

Which tract responsible for vestibulo-colic reflex?

Answer 18

Medial vestibulospinal

Question 19

Which tract responsible for vestibulo-ocular reflex?

Answer 19

Medial vestibulospinal

Question 20

(X) vestibular nuclei, via (Y), send (ipsi/contra/bi)-lateral projections to oculomotor nuclei of which CN?

Answer 20

X = superior and medial;
Y = ascending MLF
Bilateral;

CN 3, 4, 6

Question 21

Vestibulo-ocular reflex: You turn your head left. (R/L) Scarpa’s ganglion excited, thus directly exciting (X).

Answer 21

L;

X = L vestibular nuclei

Question 22

Vestibulo-ocular reflex: L vestibular nucleus excited. Where does it project?

Answer 22

1. Excitatory projection (through contralateral MLF) to R abducens nucleus
2. Inhibitory projection (via inhibitory interneurons, through ipsilateral MLF) to L abducens nucleus

Question 23

Vestibulo-ocular reflex: a L abducens nucleus sends which projections?

Answer 23

1. Excitatory projections to L motor neurons to L lateral rectus
2. Excitatory projections to excitatory interneurons that cross midline and excite R oculomotor nucleus (thus, R medial rectus)

Question 24

Which specific part of vestibular system sends afferents to vermis of cerebellum?

Answer 24

Neurons in VN

Question 25

Which specific part of vestibular system sends afferents directly to flocculo-nodular lobe?

Answer 25

Primary sensory afferents (from vestibular ganglia)

Question 26

(X) cells in the vermis and flocculo-nodular lobe send (excitatory/inhibitory) axons to (Y), an output nucleus of the cerebellum.

Answer 26

X = purkinje Inhibitory Y = fastigial nucleus

Question 27

The fastigial nucleus contributes crossed projection to (X) via (Y).

Answer 27

``` X = VN Y = uncinate fasciculus ```

Question 28

The fastigial nucleus contributes uncrossed projection to (X) via (Y).

Answer 28

``` X = VN Y = juxtarestiform body ```

Question 29

Major functional output from cerebellum to VN is (excitatory/inhibitory), particularly contributing to modulating (X),

Answer 29

Inhibitory; X = effect of LVST on antigravity muscles

Question 30

Projections from fastigial nucleus to VN is (excitatory/inhibitory).

Answer 30

Excitatory

Question 31

Semicircular canals primarily project to which VN?

Answer 31

Superior and medial

Question 32

Otolith organs primarily project to which VN?

Answer 32

Inferior and lateral

Question 33

Aside from (X) vestibular nucleus, which other brainstem inputs control extensor muscle tone? Star the stimulatory inputs

Answer 33

X = lateral* 1. Pontine* and medullary reticular formation 2. Red nucleus

Question 34

Decorticate rigidity is characterized by (X) symptoms. Where's the lesion?

Answer 34

X = involuntary overactivity of extensor muscles, except upper body; ABOVE red nucleus, impairing higher brain centers that normally indirectly inhibit extensor muscle tone

Question 35

(X) tract plays key role in vestibulo-collic reflexes, which cooperate with (Y) reflexes.

Answer 35

``` X = medial vestibulospinal Y = cervico-collic ```

Question 36

Vestibulocollic reflex functions to:

Answer 36

Stabilize head in space

Question 37

Cervico-collic reflex funcions to:

Answer 37

Stabilize head wrt trunk

Question 38

Cat falls, back-first, off chair. First, (head/body) turns due to (X) reflex. Then, (head/body) follows due to (Y) reflex.

Answer 38

Head; X = vestibulo-collic Body; Y = cervico-collic

Question 39

Pour cold water into patient's right ear produces no movement of eyes. Where's the lesion?

Answer 39

Lower brainstem (no VOR reflex)

Question 40

Pour cold water into patient's left ear. Where do you expect eyes to move?

Answer 40

To the left

Question 41

Pour warm water into patient's right ear. Where do you expect eyes to move?

Answer 41

To the left

Question 42

Patient has bilateral MLF lesion, aka (X) condition. You pour warm water into right ear. What results do you expect?

Answer 42

Internuclear opthalmegia; Left eye turns laterally; no movement in right eye