Vestibular System Flashcards
1
Q
Functions of the vestibular system
A
- sensory info about head movements & head position relative to gravity
- gaze stabilization: control of eye movements when head is moving
- postural adjustments/balance
- autonomic functions
2
Q
Organization of the vestibular system
A
- vestibular apparatus/inner ear/labyrinth –> CN VII –> 4 vestibular nuclei (pons/medulla) –> 6 outputs involving vestibular information
3
Q
Vascular supply to vestibular system
A
- labyrinthine artery
- mostly branches off of the AICA
- occlusion can cause dizziness & auditory symptoms
- divides into Anterior vestibular artery and Common cochlear artery
- Anterior vestibular artery: dizziness symptoms only, supplies the vestibular nerve, utricle, horizontal, & anterior semicircular canals
- Common cochlear artery: dizziness and auditory symptoms, supplies the cochlea, saccule, & posterior semicircular canal
4
Q
Vestibular apparatus
A
- ampulla of the 3 semicircular canals
- macula which contains the article & saccule and otoconia (crystals)
- hair cells in the semicircular canals bend as endolymph pushes cupola with angular movements
- hair cells in utricle/saccule bend due to gravity or with linear acceleration/deceleration
5
Q
Orientation of the semicircular canals
A
- Horizontal: points 30 degrees up and detects head rotation
- Posterior: angled the same as your ear
- Anterior: perpendicular to the posterior
- Anterior and posterior canals detects diagonal movements
6
Q
Activation/inhibition of hair cells by bending
A
- resting rateis 90 spikes/sec
- deflection of the hair cell towards the kinocilia = excitatory output
- deflection of the hair cell away from the kinocilia = inhibitory output
7
Q
Turning your head to the right
A
- semicircular canals work in pairs to detect angular movements
- horizontal canals are being used
- right SC canal will be activated while left SC canal will be inhibited
8
Q
What canals talk to one another
A
- horizontal canals talk to each other
- left anterior and right posterior talk to one another (LARP)
- right anterior and left posterior talk to each other (RALP)
9
Q
Utricle and saccule
A
- they detect linear movements while SC canals detect rotational movements
- 4 total meaning one pair in each ear
- utricle is oriented horizontally, responds to horizontal linear acceleration/deceleration & forward/backward head tilts
- saccule is oriented vertically, responds to vertical linear movements & leaning sideways
10
Q
Dizziness/Vertigo
A
- illusion of motion/spinning
- impaired gaze stability with head movements & blurry vision due to impaired VOR
- can be associated with nystagmus which could be spontaneous or triggered by positional changes
11
Q
Nystagmus
A
- repetitive involuntary beating movements due to inaccurate signals coming in from peripheral vestibular systems (SC or CN VIII) or impairments in central vestibular processing centers (brainstem or cerebellum)
- more severe in peripheral than central lesions
- can be physiologic
12
Q
Laws of nystagmus for peripheral lesion
A
- Alexander’s Law: the amplitude of the nystagmus increases when the eye moves in the direction of the fast phase
- Ewald’s Law: movement of the eyes during nystagmus occur in the plane of the stimulated canals
13
Q
Vestibular neuritis
A
- a peripheral lesion in the vestibulocochlear nerve
14
Q
Left posterior canal BPPV
A
- a peripheral lesion with otoconia crystals dislodged from utricle/saccule that have entered the left posterior canal
- there will be a latency or a duration & then the nystagmus will stop
15
Q
End gaze nystagmus
A
- normal
- everyone has a little nystagmus when straining the eye to look at end range
