Neuro - VESTIBULAR FUNCTION

Question 1

how many semi-circular canals constitute the vestibular apparatus?

Answer 1

3

Question 2

which parts of the vestibular apparatus contain sensory hair cells?

Answer 2

ampulla of semi-circular canals (swelling at their base), utricle (where the semi-circular canals join) and saccule

Question 3

which are the otolith organs?

Answer 3

utricle and saccule collectively

Question 4

what do the otolith organs detect?

Answer 4

linear acceleration

Question 5

what does the utricle detect on its own?

Answer 5

back/front tilt of the head

Question 6

what does the saccule detect on its own?

Answer 6

vertical movement

Question 7

what do the semi-circular canals detect?

Answer 7

rotational acceleration

Question 8

what are the sensory receptors/hair cells called in the ampulla? what does it consist of?

Answer 8

cristae, consists of a flexible gelatinous structure called the cupula that stretches along the entire length of the ampulla and detects endolymph movement within the canals. The hair cells are embedded in the cupula

Question 9

what are the two types of hair cells?

Answer 9

a single large kinocilium and a set of progressively smaller stereocilia

Question 10

distortion of the cilia in the direction of the kinocilium causes depolarisation/hyperpolarisation? what effect does this have on the vestibular nerve?

Answer 10

depolarisation, increased discharge of AP in the vestibular nerve

Question 11

distortion of the cilia away from the kinocilium causes depolarisation/hyperpolarisation?

Answer 11

hyperpolarisation, decreased discharge of AP in the vestibular nerve

Question 12

where does the integration of all this sensory information take place?

Answer 12

cerebellum

Question 13

what is the name given to the sensory apparatus of the utricle and saccule?

Answer 13

the maculae

Question 14

in which plane are the macula of the utricle orientated?

Answer 14

horizontal plane

Question 15

in which plane are the macula of the saccule orientated?

Answer 15

vertical plane

Question 16

where do you find otolith crystals?

Answer 16

in the otolith membrane (a gelatinous mass made up of 1 kinocilium and a series of stereocilia, all belonging to the macula)

Question 17

for the utricle macula, does a backward or forward tilt cause an increase discharge of AP to the vestibular nerve?

Answer 17

backwards causes the cilia to move towards the kinocilium and therefore increases depolarisation, therefore increasing discharge of AP to the vestibular nerve

Question 18

where do the sensory afferents of the vestibular nerve terminate?

Answer 18

vestibular centres of medulla

Question 19

which other muscles also send information to the vestibular centres of the medulla?

Answer 19

limb proprioception, neck and eye muscles

Question 20

what is kinaesthesia?

Answer 20

perception of body position and movement

Question 21

what do the tonic labyrinthine reflexes do? what information do they use?

Answer 21

keep the axis of the head in a constant relationship with the rest of the body. Uses information from maculae and neck proprioceptors

Question 22

what do the dynamic righting reflexes do? what information do they use?

Answer 22

rapid postural adjustments that are made to stop you falling when you trip

Question 23

what are the different vestibular-ocular reflexes?

Answer 23

• static reflex (when you tilt your head, your eyes intort/extort to compensate)
• dynamic vestibular nystagmus (series of saccadic eye movements that rotate the eye against the direction of rotation of the head and body so that the original direction of gaze is preserved despite head rotating)

Question 24

which vestibular reflex can be used to test vestibular function?

Answer 24

vestibular nystagmus

Question 25

which are the ANS symptoms?

Answer 25

nausea and vomiting
pallor and sweating
decreased BP and dizziness

Question 26

which drug is the inner ear sensitive to?

Answer 26

streptomycin