Vestibular Flashcards
(26 cards)
What three systems enable balance?
vestibular, proprioceptive, and visual
Where is the vestibular system located?
In petrous portion of temporal bone lateral to the internal acoustic meatus
Three divisions of vestibular system
1) semicircular canals (ant, post, horizontal)
2) Utricle (connects 3 canals)
3) saccule (continuous with cochlea)
What are the 2 otolithic membranes
1) utricle = good for horizontal acceleration sensing (and gravity)
2) saccule = good for vertical sensing
The two are split by vestibular nerve
Name for the gelatinous covering of hair cells in semicircular canal
cupola
Name of the swelling in which the hair cells of the semicircular canals are located
ampulla
What does a greater difference perceived (by the cortex) velocity difference mean?
faster velocity of endolymph
hair cell (kinocilium) planes: the HORIZONTAL canals are oriented \_\_\_\_\_\_\_ the utricle
towards
the ANTERIOR and POSTERIOR canals are oriented ________ the utricle
away from
Anterior canal on the right is paired with the ___________ on the LEFT
posterior canal
and vice versa
Depolarization
Increased impulse frequency, excitation, increased action potentials in the vestibular nerve (CN8)
stereocilia bends TOWARDS kinocilium
Hyperpolarization
Decreased impulse frequency, inhibition, decreased action potentials
stereocilia bends AWAY from kinocilium
What is the function of the utricle?
detects upright position and head tilt; considered primary gravity sensor (also detects horizontal linear acceleration
What is the function of the saccule?
detects general orientation and vertical linear acceleration
Which is the primary gravity sensor?
utricle
What is the route of hearing to the CNS?
hair cell –> bipolar cell (APs) –> vestibular ganglion –> CN8 –> vestibular nuclei
What are the two divisions of the vestibular ganglion?
1) Superior (utricle, ant. saccule, horizontal and ant. SCC)
2) Interior (post. sacculr and post. SCC)
*remember that inferior does the two posterior S’s (saccule and semicircular canals) and superior does the rest
What are the 4 divisions of the vesibular nuclei?
1) Lateral (utricle and saccule) - does posture and vestibulo-ocular reflexes
2) Medial and Superior (SCC and some fibers from utricle) - does vestibulo-ocular reflexes and coordinates eye and neck
3) Inferior (all areas) - projects to cerebellum and coordinates balance with voluntary movements (spinal nuc)
What do the ascending fibers of the MLF control?
eye movements
What do the descending fibers of the MLF control?
head and neck movements
What part of the cerebellum does the vestibular system communicate with?
flocculonodular system
Direct input from SCC and otolithic organs
Indirect input from vesibular nuclei, lat. geniculate, sup. colliculus, pontine nuclei
What does the cerebellum project back to?
vestibular nuclei (controls movement)
Main points of the lateral vestibulospinal tract
1) Uncrossed projection
2) Entire length of cord
3) maintains balance by acting on limbs
Main points of medial vestibulospinal tract
1) Bilateral projection
2) Cervical spinal cord only
3) maintains head erect (neck muscles)
