Vestibular

Question 1

What three systems enable balance?

Answer 1

vestibular, proprioceptive, and visual

Question 2

Where is the vestibular system located?

Answer 2

In petrous portion of temporal bone lateral to the internal acoustic meatus

Question 3

Three divisions of vestibular system

Answer 3

1) semicircular canals (ant, post, horizontal)
2) Utricle (connects 3 canals)
3) saccule (continuous with cochlea)

Question 4

What are the 2 otolithic membranes

Answer 4

1) utricle = good for horizontal acceleration sensing (and gravity)
2) saccule = good for vertical sensing

The two are split by vestibular nerve

Question 5

Name for the gelatinous covering of hair cells in semicircular canal

Answer 5

cupola

Question 6

Name of the swelling in which the hair cells of the semicircular canals are located

Answer 6

ampulla

Question 7

What does a greater difference perceived (by the cortex) velocity difference mean?

Answer 7

faster velocity of endolymph

Question 8

hair cell (kinocilium) planes:
the HORIZONTAL canals are oriented \_\_\_\_\_\_\_ the utricle

Answer 8

towards

Question 9

the ANTERIOR and POSTERIOR canals are oriented ________ the utricle

Answer 9

away from

Question 10

Anterior canal on the right is paired with the ___________ on the LEFT

Answer 10

posterior canal

and vice versa

Question 11

Depolarization

Answer 11

Increased impulse frequency, excitation, increased action potentials in the vestibular nerve (CN8)

stereocilia bends TOWARDS kinocilium

Question 12

Hyperpolarization

Answer 12

Decreased impulse frequency, inhibition, decreased action potentials

stereocilia bends AWAY from kinocilium

Question 13

What is the function of the utricle?

Answer 13

detects upright position and head tilt; considered primary gravity sensor (also detects horizontal linear acceleration

Question 14

What is the function of the saccule?

Answer 14

detects general orientation and vertical linear acceleration

Question 15

Which is the primary gravity sensor?

Answer 15

utricle

Question 16

What is the route of hearing to the CNS?

Answer 16

hair cell –> bipolar cell (APs) –> vestibular ganglion –> CN8 –> vestibular nuclei

Question 17

What are the two divisions of the vestibular ganglion?

Answer 17

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

Question 18

What are the 4 divisions of the vesibular nuclei?

Answer 18

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)

Question 19

What do the ascending fibers of the MLF control?

Answer 19

eye movements

Question 20

What do the descending fibers of the MLF control?

Answer 20

head and neck movements

Question 21

What part of the cerebellum does the vestibular system communicate with?

Answer 21

flocculonodular system

Direct input from SCC and otolithic organs
Indirect input from vesibular nuclei, lat. geniculate, sup. colliculus, pontine nuclei

Question 22

What does the cerebellum project back to?

Answer 22

vestibular nuclei (controls movement)

Question 23

Main points of the lateral vestibulospinal tract

Answer 23

1) Uncrossed projection
2) Entire length of cord
3) maintains balance by acting on limbs

Question 24

Main points of medial vestibulospinal tract

Answer 24

1) Bilateral projection
2) Cervical spinal cord only
3) maintains head erect (neck muscles)

Question 25

Function of vestibulo-ocular reflex

Answer 25

stabilizes image on retina during rotation of head and faster than visual tracking

ATTENUATES OVER TIME

Question 26

What is nystagmus?

Answer 26

rhythmic back and forth movement of eyes (dancing of eyes)

tested for by ear levage (Cold Opposite Warm Same COWS)
fast phase directed towards where you put water
ex: inject hot in right ear, fast phase directed right, slow phase directed left