09 16 2014 Vestibular System Flashcards Preview

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Flashcards in 09 16 2014 Vestibular System Deck (32)
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Vestibular system tasks?

1. controls reflexive eye movements
-cerebellum and oculomotor nuclei

2. Vestibulo-ocular reflexes keep the eyes still when the head moves

3. vestibulospinal reflexes : enable the skeletomotor system to compensate for head movements


Symptoms of vestibular system disease?

Vertigo vs. dizziness (with feeling of the world spinning)

Nauseau, vomiting, pallor, perspiration

Difficulty walking

Sensation of spinning or rhythmic movements

Nystagmus (jerky eye movements



vestibular damage that makes it difficult or impossible to fixate on visual targets while head is moving.

-feel like the words is spinning around you


Blood supply to labyrinth?

What would happen if there is a stroke in this area?


-sudden hearing loss and vertigo


Semicircular canals

-angular acceleration : rotation
-functions in paris with opposite canal on opposite ear

-hair cells are in ampulla. Hair cells in ampule are covered by a gelatinous mass called a CUPULA.

-Cupula has weight and when head moves it lags behind and bends hair cells


Direction of hair cells in Semicircular canals

Anteriror : Facing up and away from utricle

Horizontal: slightly down and towards utricle.

Posterior: Horizontal


-what is in it?

Macula: thick sensory epithelium with hair cells oriented in the horizontal plane.

Also has otoconia (calcium carbonate crystals) embedded in otolithi membrane
-displacement = action potential



Macula: thickened epithelium with hairs oriented in the vertical plane

-responds to linear acceleration in vertical plane.


Movement that Saccule and Utricle comprehend?

Linear acceleration of head (in any direction) AND static head position



utricle and saccular areas are divided by a striola-- just an area that divides hair population having opposite polarities



Benign Paroxysmal positional vertigo

-otoconia detaches from otolithic membrane of the utricle and it gets stuck in the semicircular canal.
-- obstruct flow of cupula

Usually unilateral but can sometimes be bilateral


Lateral vestibular nucleus controls what?

posture, vestibulo-spinal reflexes


medial and superior vestibular nuclei control what?

vestibulo-ocular reflexes; vestibulo-cervical reflexes


Inferior vestibular nucleus does what?

integration of inputs from the vestibular labyrinth and the cerebellum


Medial and superior vestibular nuclei innervation?

-receives fibers predominantly from the semicircular canals
-efferents include MLF, oculomotor nuclei, and cuddly to spinal cord

-Medial vestibular nuclues --> medial vestibular tract = vestibulo-cervical reflexes.

Medial nucleus efferents are excitatory
Superior nucleus efferents are inhibitory


Lateral vestibular nucleus innervation?

aka Deiter's nucleus

-Afferents from semicircular canals and otolithic organs.

Efferents mostly to the lateral spinovestibular tract.

Largely conceded with postural control


Inferior (descending) vestibular nucleus innervation?

What is this nucleus mostly concerned with?

Afferents from otolithic organs and cerebella cortex (purkinje cells)

Efferents mostly to cerebellum and reticular formation, contralateral vestibular nuclei and spinal cord.

Concerned with integrating central motor signals with vestibular input


Lateral vestibulospinal tract

Principal pathway by which otolithic organs can regulate bodies extensor organs

major source: LVN
minor contributor: SpVN


Medial Vestibulospinal tract

projects through MLF

Major source: MVN

Mainly cervical
Vestibulo-cervical reflexes


Vestibulothalamic projections

ascending pathway (poorly understood)

-Ventroposterolateral (VPL), pars oralis
-Bilateral projections
-tend to arise from the medial vestibular nucleus.

Other targets are VP, VL, and intralaminar nuclei.



typical to side contralateral to the dysfunction of vestibular apparatus

involuntary rhythmic movements of the eyes consisting of a rapid movement in one direction and a slow movement in the opposite direction


Caloric test

irrigating the external auditory meatus with warm or cold water.

Nystagmus towards warm water and away from cold water.


Optikinetic Nystagmus

fast component in the opposite direction to that of the moving lines

-ex. looking at telephone poles while in passenger seat in car


Vestibular-occular-reflex (VOR)

particular system that produces eye movements that counter movements of head

-permit gaze to remain fixed on a particular point.


Vertigo vs. dizziness

vertigo-- spinning sensation of movement

Dizziness: light headedness, nausea, unsteadiness on one's feet


vestibular neuritis

inflammation of vestibular ganglia or fever due to a viral infection or idiopathic inflammation


acoustic neuroma

cerebellopontine angle tumors

onset: 50 yrs of age

Occurs at the point where CN 8 enters the internal auditory meatus.
-early symptom: tinnitus (unilateral) and unsteadiness


positional testing

helps identify BPPV of any of the semicircular canals and other causes for positional dizziness


central vs. peripheral vertigo
and nystagmus

Peripheral lesions: delay of 2- 5 secs before the onset of nystagmus and vertigo.
-horizontal or rotational
-fades within 30 secs
-fades with adaptation to tests

Central lesions: nystagmus and vertigo begin immediately and there is no adaptation.
-horizontal or rotary nystagmus
** Vertical nystagmus, nystagmus that changes directions while remaining in the same position, nystagmus in the absence of vertigo is ONLY CENTRAL.


Gaze nystagmus

have patient gaze no more than 30 degrees from front. If there is a problem, the nystagmus is contralateral to the dysfunctional side