Week 1: Anatomy and Physiology of the Vestibular System Flashcards
What are the functions of the vestibular system?
- Position and perceiving self-motion
- Sensory orientation
- Postural responses
- Stabilizing the head
Head movements are detected by the _______ and transmitted via the _______ to the _______, which then controls ________ to ________.
Cupula Vestibular nerve Brain Eye movements Stabilize gaize
What should the ratio of eye to head movement (GAIN) be? What does abnormal gain cause?
1:1
Blurry vision or vertigo
What does the Vestibuo-Ocular Reflex (VOR) do?
Stabilizes eye in space, necessary to see while head is in motion
What are the 2 components of VOR?
Linear and angular
What does the Vestibulo-Spinal Reflex (VSR) do?
Stabilizes body, helps maintain desired orientation to environment
What does the Cervico-Ocular Reflex (COR) do?
weak, does not play a direct role in gaze stability, may help VOR compensate via proprioceptors and somatosensory receptors
Where do the propriocecptors and somatosensory receptors for the COR arise?
C1-C2 dorsal nerve roots
What does the Cervicocollic Reflex (CCR) do?
provides head stability, contraction of stretched muscles to align head
What does the Cervicospinal Reflex (CSR) do?
acts in conjunction with the VSR, provides postural stability through the limb activation
What are the three axes of rotation?
roll, pitch, yaw
What are the three axes of translation?
AP, Lateral, Vertical
______ are angular rate sensors.
Semicircular Canals
______ are linear accelerometers
Otoliths (Utricle and Saccule)
What are the functions of the peripheral vestibular system?
Stabilization of visual images on the fovea of the retina during head movement to allow clear vision, maintain postural stability- especially during head movement, provide information used for spatial orientation
What are the components of the peripheral vestibular system?
Semicircular canals, utricle, saccule, CN VII (vestibulocochlear nerve)
What are the orientations of the semicircular canals?
Anterior, Posterior, Horizontal
What is the bony labyrinth composed of?
3 semicircular canals, the cochlea, and the vestibule
What is the bony labyrinth filled with?
perilymphatic fluid
What is the membranous labyrinth?
suspended in the bony section and contains portions of the canals and the utricle and saccule.
What is the membranous labyrinth filled with?
endolymphatic fluid
What are the motion sensors?
Ampulla and Otolith Organ
What are cupula?
hair cells
What do cupula do?
convert displacement into neuro firing thru bending of hair cells to detect linear/angular motion
What contains the otoconia?
utricle and saccule
What are otoconia made out of?
calcium carbonate
What do shifts in the otoconia cause?
set off neuro firing detecting gravity and acceleration
Hair cells protrude their processes into a gelatinous matrix called ______.
macula
The firing rate of the otoconia is ______ for ipsilateral linear head movement or tilt.
Increased
The firing rate of the otoconia is ______ for contralateral linear head movement or tilt.
Decreased
________ measure linear acceleration and lateral tilt
Otoliths
What are the 2 targets for vestibular input?
vestibular nuclear complex and the cerebellum
_______ is the main adaptive processor.
cerebellum
_______ is the “back up” system for the adaptation of the gain of the VOR
cerebellum
What is the main supplier of both the peripheral and central vestibular systems?
vertebrobasilar artery
Occlusion of which arteries causes clinical syndromes with vestibular components?
basilar, labyrinthine, AICA, PICA
Why are cerebella strokes the most commonly missed?
symptoms may mimic vertigo
Only ____ sec of ischemia can cause permanent damage
15
maintains gaze direction of the eyes and visual acuity during activities involving active head and body movements
gaze stabilization system
keeps body in balance while an individual stands and actively moves in daily life
postural stabilization system
