06b: Central Vestibular System Flashcards
Vestibular, aka (X), ganglion sends axons into CNS that courses medial to (Y) structure(s).
X = Scarpa's Y = cochlear nuclei and ICP
Vestibular axons enter CNS and terminate in which subdivisions of vestibular nucleus?
All 4 major subdivisions
List the subdivisions of vestibular nucleus, named based on their location wrt (X).
X = cerebellum;
Inferior, superior, medial, lateral
A lesion affecting (X) surface of (Y) brainstem structures is likely to impact vestibular system.
X = dorsal;
Y = medulla and pons
Through (X), a subdivision of (Y), the vestibular ganglion, unlike any other sensory system, sends axonal projections directly to (Z).
X = juxtarestiform body; Y = ICP Z = vestibular cerebellum
The vestibular cerebellum is composed of which region(s)?
Flocculo-nodular lobe
Main central projections from vestibular nuclei are to (X).
X = SC, cerebellum, oculomotor nuclei
T/F: Some neurons in vestibular nuclei also send axons to thalamus.
True
Deiter’s nucleus, aka (X), projects to (Y) via (Z) tract.
X = lateral vestibular nucleus; Y = interneurons/motor neurons along entire length of SC (antigravity muscles) Z = lateral vestibulospinal tract
Head and trunk tilt to the right. Which side of vestibular system activated?
Right
Head and trunk tilt to the right. Which lower-extremity muscles activated on R/L sides by (X) tract?
R: Extensors
L: Flexors
X = lateral vestibulo-spinal
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?
Ipsilateral Lateral vestibulospinal tract
Vestibulospinal reflexes are coordinated with (X) reflexes. What does each respond to?
X = cervicospinal
VS: responds to head tilt
CS: responds to trunk tilt
Vestibular nuclei and (X) tract receive strong (stimulatory/inhibitory) influences from higher brain centers.
X = lateral vestibulospinal tract;
Inhibitory
Decerebrate rigidity is characterized by (X) symptoms. Where’s the lesion?
X = involuntary overactivity of extensor muscles, including upper body;
BELOW red nucleus, impairing higher brain centers that normally indirectly inhibit extensor muscle tone
Medial vestibular nucleus projects (up/down) to:
Up: extraocular motorneurons
Down: neck motorneurons
Medial vestibulospinal tract, aka (X), projects (ipsi/contra/bi)-laterally to which part(s) of SC?
X = descending MLF
Bilaterally;
Cervical segments
Which tract responsible for vestibulo-colic reflex?
Medial vestibulospinal
Which tract responsible for vestibulo-ocular reflex?
Medial vestibulospinal
(X) vestibular nuclei, via (Y), send (ipsi/contra/bi)-lateral projections to oculomotor nuclei of which CN?
X = superior and medial;
Y = ascending MLF
Bilateral;
CN 3, 4, 6
Vestibulo-ocular reflex: You turn your head left. (R/L) Scarpa’s ganglion excited, thus directly exciting (X).
L;
X = L vestibular nuclei
Vestibulo-ocular reflex: L vestibular nucleus excited. Where does it project?
- Excitatory projection (through contralateral MLF) to R abducens nucleus
- Inhibitory projection (via inhibitory interneurons, through ipsilateral MLF) to L abducens nucleus
Vestibulo-ocular reflex: a L abducens nucleus sends which projections?
- Excitatory projections to L motor neurons to L lateral rectus
- Excitatory projections to excitatory interneurons that cross midline and excite R oculomotor nucleus (thus, R medial rectus)
Which specific part of vestibular system sends afferents to vermis of cerebellum?
Neurons in VN
Which specific part of vestibular system sends afferents directly to flocculo-nodular lobe?
Primary sensory afferents (from vestibular ganglia)
(X) cells in the vermis and flocculo-nodular lobe send (excitatory/inhibitory) axons to (Y), an output nucleus of the cerebellum.
X = purkinje
Inhibitory
Y = fastigial nucleus
The fastigial nucleus contributes crossed projection to (X) via (Y).
X = VN Y = uncinate fasciculus
The fastigial nucleus contributes uncrossed projection to (X) via (Y).
X = VN Y = juxtarestiform body
Major functional output from cerebellum to VN is (excitatory/inhibitory), particularly contributing to modulating (X),
Inhibitory;
X = effect of LVST on antigravity muscles
Projections from fastigial nucleus to VN is (excitatory/inhibitory).
Excitatory
Semicircular canals primarily project to which VN?
Superior and medial
Otolith organs primarily project to which VN?
Inferior and lateral
Aside from (X) vestibular nucleus, which other brainstem inputs control extensor muscle tone? Star the stimulatory inputs
X = lateral*
- Pontine* and medullary reticular formation
- Red nucleus
Decorticate rigidity is characterized by (X) symptoms. Where’s the lesion?
X = involuntary overactivity of extensor muscles, except upper body;
ABOVE red nucleus, impairing higher brain centers that normally indirectly inhibit extensor muscle tone
(X) tract plays key role in vestibulo-collic reflexes, which cooperate with (Y) reflexes.
X = medial vestibulospinal Y = cervico-collic
Vestibulocollic reflex functions to:
Stabilize head in space
Cervico-collic reflex funcions to:
Stabilize head wrt trunk
Cat falls, back-first, off chair. First, (head/body) turns due to (X) reflex. Then, (head/body) follows due to (Y) reflex.
Head;
X = vestibulo-collic
Body;
Y = cervico-collic
Pour cold water into patient’s right ear produces no movement of eyes. Where’s the lesion?
Lower brainstem (no VOR reflex)
Pour cold water into patient’s left ear. Where do you expect eyes to move?
To the left
Pour warm water into patient’s right ear. Where do you expect eyes to move?
To the left
Patient has bilateral MLF lesion, aka (X) condition. You pour warm water into right ear. What results do you expect?
Internuclear opthalmegia;
Left eye turns laterally; no movement in right eye
