Vestibular System

Question 1

functions of the vestibular system

Answer 1

move the eyes

neck and body muscle coordination

perception of body orientation

Question 2

position sense relies on collaboration of..

Answer 2

vestibular system

visual system

proprioception

Question 3

what does Romberg’s sign test? (standing up straight and closing eyes)

Answer 3

vestibular and proprioception

Question 4

major structures of the vestibular system and their functions

Answer 4

semicircular ducts - detect angular acceleration

utricle and saccule - detection of linear acceleration

Question 5

structures of the macula inside the utricle or saccule

Answer 5

otoconium, otolithic membrane, hair cell, supporting cell

Question 6

what happens when the head tilts to the right?

Answer 6

otoconium will move to the right, causing stereocilia on top of a hair cell to bend to the right.

this changes the membrane potential and alters glutamate release from hair cells, initiating a signal in the bipolar cells of the vestibular ganglion

Question 7

names of the semicircular ducts

Answer 7

anterior, posterior, lateral/horizontal

Question 8

what is the significance of the 3 semicircular canals arranged at a right angle to one another?

Answer 8

duplicated signals for each head movement, thus precise head positioning

Question 9

what fluid is found inside the semicircular canals?

Answer 9

endolymph, ahir cells in the ampullas, activated by endolymph movement

Question 10

structure that hair cells sit on; what are they embedded in?

Answer 10

crista; semifluid cupula

Question 11

characteristics of endolymph

Answer 11

similar to intracellular fluid, high in K low in Na

Question 12

why are they called dendrites of vestibular ganglion cells instead of axons?

Answer 12

they pick up sensory info

Question 13

hair cells in the utricle/saccule are activated by

Answer 13

otolith movement (this helps detet linear acceleration)

Question 14

what happens when otoliths get into the semicircular canals?

Answer 14

causes vertigo in the patient

Question 15

angular acceleration that semicircular canals respond to is actually a response to a change of..

Answer 15

speed

Question 16

higher speed contributes to this type of firing frequency

Answer 16

higher

Question 17

if speed is constant, the frequency is

Answer 17

background firing frequency

Question 18

vestibular connections into the CNS

Answer 18

cerebellum, vestibular nuclei to spinal cord, thalamus to somatosensory cortex, CN 3, 4, 6, reticular formation (pons, medulla)

Question 19

the vestibular connections into the CNS function to

Answer 19

move the eyes

neck and body muscle coordination

perception of body orientation

Question 20

the name for the reflex where your head tilts right, eyes move left and vice versa (unconscious)

Answer 20

vestibule-ocular reflex

oculocephalic reflex

doll’s eye reflex

Question 21

steps of the vestibule-ocular reflex

Answer 21

signals generated in the ampula of horizontal semicircular canals because of endolymph movement, info passes thru vestibular ganglion to nucleus to CN 6, via MLF the info is relayed to CN 4 and CN 3 nuclei

right eye is pulled to the left when CN 3 commands MR to pull

right CN 6 nucleus also talks to lateral rectus to pull, left eye pulled left, right eye pulled left.

Question 22

brainstem structures important for vestibular-ocular movement connection

Answer 22

vestibular system, MLF, CN 3, 4, 6 nuclei

Question 23

when the vestibule-ocular reflex is used to test brainstem function in comatose patients its called

Answer 23

oculocephalic reflex

Question 24

what’s the caloric test?

Answer 24

same vestibular-ocular reflex initiated by irrigating the patient’s warm/cold water; initiates nystagmus due to endolymph movement in the semicircular canals

Question 25

direction of nystagmus is defined by the..

Answer 25

fast phase (if eyes jerk to the right rapidly, its right-beating nystagmus)

Question 26

3 ways to induce nystagmus

Answer 26

rotation, cold/warm water into ear, optokinetic

Question 27

the direction of endolymph flow =

Answer 27

direction of tracking = direction of slow phase nystagmus

Question 28

cold water into right ear =…

warm water into right ear = ..

Answer 28

left-beating nystagmus

right-beating nystagmus

Question 29

what does COWS stand for

Answer 29

Cold Opposite, Warm Same.

Question 30

in a normal person the slow phase is controlled by… the fast phase controlled by…

Answer 30

slow phase= brainstem

fast phase=cerebrum

Question 31

so in a coma patient with cerebrum not functioning, which phase is apparent?

Answer 31

slow phase only, if brainstem is intact

Question 32

induction of nystagmus by looking at a continuously moving object

Answer 32

optokinetic nystagmus or railroad nystagmus

Question 33

what is the optokinetic reflex used to test?

Answer 33

factitious blindness since we cannot suppress this reflex if visual pathway is in tact

Question 34

what cranial nerves travel through internal auditory meatus?

Answer 34

CN 7 and 8

Question 35

common tumor at lower pons in the internal auditory meatus

Answer 35

acoustic nerve schwannoma