Vestibular Lecture Flashcards
Flowchart of Vestibular Function
Sensory input (vestibular, somatosensation, vision) –> Cerebellum and vestibular nuclei –> motor output (reflexes, postural, eye movement)
Peripheral Components
- Membranous Labyrinth, sits in…
- Bony Labyrinth, supported by…
- Perilymph
What is perilymph?
Similar to CSF with an increased Na:K ratio
Peripheral (Sensory) components
- 3 Semicircular Canals (SCC): Anterior, Posterior and Horizontal canals
- 2 Otolith Organs: Utricle and Saccule located within the Vestibule
- Other important landmarks: 8th Cranial Nerve, Endolymphatic Sac, Round & Oval Windows
Semi Circular Canals
- Oriented in 3 canal planes
- Each canal is paired with a canal on the opposite side
- Anterior canal with opposite Posterior canal
- Two Horizontal canals
Ampullofugal Stimulation
- displacement of cupola away from utricle
- excitation
Ampullopetal Stimulation
- Displacement of cupola towards utricle
- inhibition
what is the taller hair cell called?
Kinocillium
what is entering the hair cell that causes the channel to open?
glutamate and aspartate
Does excitatory stimuli or inhibitory stimuli cause a greater response?
- excitatory
- If you turn your head very quickly, your inhibiting ear may not be inhibiting enough –> fast motions become a problem
Nystagmus at rest: non-pathologic
L: 90 spikes/sec
R: 90 spikes/sec
Nystagmus at rest: pathologic
L: 40 spikes/sec
R: 90 spikes/sec
**will feel like you are turning to the right
What are the 2 Otoliths
Utricle and Saccule
Oriented in 2 different planes
What do the utricle and saccule detect?
linear acceleration and tilt
Is the vestibular nerve considered part of the periphery or central?
periphery
Where do afferent signals of the vestibular nerve project?
- From scarpa’s ganglion through the internal auditory canal with cochlear and facial nerve (sensory branch) and labyrinthine artery
Where does superior vestibular nerve go?
anterior and horizontal canals
utricle
where does the inferior vestibular nerve go?
posterior canal and saccule
Where does the vestibular nerve enter the brainstem?
at the ponto-medullary junction
“root entry zone”
what does PICA supply
inferior portion of the cerebellar hemispheres
dorsolateral medulla
what does the basilar artery supply?
pons
what does the AICA supply?
peripheral vestibular system via labyrinthine artery
an ICA stoke is likely to cause what?
vestibular issues
From where do nuclei receive input?
peripheral vestibular system, vision, and somatosensory afferents