4 - Vestibular Function

Question 1

what is the role of the vestibular system?

Answer 1

• detects forces generated by movement and translates this into a sense of balance
• provides info about the positon of the head in space

Question 2

where is the vestibule located?

Answer 2

between the semi-circular canals and cochlea

Question 3

what does the vestibule contain

Answer 3

utricle and saccule

Question 4

the utricle and saccule have equilibrium receptors called what?

Answer 4

maculae

Question 5

what does the saccule detect?

Answer 5

vertical acceleration/sensation of moving upwards

Question 6

what does the utricle detect?

Answer 6

horizontal acceleration/moving forwards

Question 7

what are the otolith organs?

Answer 7

utricle and saccule

Question 8

what do the semi circular canals detect? what do the otolith organs detect?

Answer 8

semi-circular canals - angular acceleration
otolith organs - linear acceleration

Question 9

what system do the semi-circular canals form? what system do the otolith organs form?

Answer 9

semi-circular canals - dynamic system
otolith organs - static system

Question 10

what are otoconia?

Answer 10

calcium carboate crystals that form the striola which in turns rests on the otolithic membrane

Question 11

how does the otolithic membrane detect changes in linear acceleration?

Answer 11

• head moves
• striola on otolithic membrane (gelatinous layer) moves
• creates sensory transduction
• bends hair cells embedded in the otolithic membrane
• creates senstation of acceleration

Question 12

semi-circular canals are essential for the coordination of what organ?

Answer 12

the eyes

Question 13

label which semi-circular canal is responsible for rolling, yawing and pitching:

Answer 13

Question 14

how do the semi-circular canals detect angular acceleration?

Answer 14

• endolymph movement displaces cupula (gelatinous mass)
• causes physical strain on hair cells
• deflection towards the kinocilium increases firing, deflection away from the kinocilium decreases it

Question 15

what is the kinocilium?

Answer 15

longest and thickest hair cells within the stereocilia

Question 16

how is signal transduction controlled in semi-circular canals?

Answer 16

mechanically gated channels

Question 17

what type of transmission occurs in the semi-circular canals?

Answer 17

glutamatergic

Question 18

what is the purpose of the vestibulo-ocular reflex?

Answer 18

• prevents retinal slip
• as the head rotates left, the eyes rotate right etc

Question 19

what is nystagmus?

Answer 19

repetitive and involuntary eye movements that alternate beween slow eye movement and rapid saccadic movement

Question 19

what is slow phase eye movement mediated by?

Answer 19

vestibulo-ocular pathway

Question 20

what is fast phase eye movement triggered by?

Answer 20

cerebral cortex

Question 21

what phase eye movement is common in a comatose patient?

Answer 21

slow phase is present, but not fast phase

Question 22

what is the role of the vestibulo-spinal tract?

Answer 22

basic balance and postural control

Question 23

how do axons from the vestibular nuclei descend?

Answer 23

ipsilaterally

Question 24

where do axons from the vestibular nuclei synapse?

Answer 24

on the lower motor neurons

Question 25

activity in the vestibular nuclei is modulated by what?

Answer 25

the cerebellum

Question 26

what is meniere’s disease?

Answer 26

increase in endolymph pressure that disrupts signal transduction resulting in tinnitus, nausea, and spontaneous nystagmus

Question 27

what is benign paroxysmal positional vertigo?

Answer 27

dislodged bits of otolith stimulate the cupula in the posterior ssc and cause vertigo

Question 28

what is motion sickness?

Answer 28

mismatch between signals sent from visual and vestibular systems

Question 29

LabEl the otolith membrane

Answer 29

Question 30

Label the vestibular labyrinth

Answer 30

Question 31

Label the semi circular canals

Answer 31