vestibular function

Question 1

what do vestibular labryinths sense?

Answer 1

head motion

Question 2

how many axes of rotation are detected by the semicircular canal?

Answer 2

one of the three

Question 3

what does the otolith ( utricle and saccule detect)?

Answer 3

3 axes of translational movement and force of gravity

Question 4

what is the purpose of the vestibulo-ocular -reflex?

Answer 4

to keep the visual scene steady on the retina during head movements

Question 5

what structure is the ampulla apart of and what are some of it’s properties?

Answer 5

it is apart of the semicircular canal of the inner ear and it has hair cells w/ directional orientation

Question 6

what is the semicircular canal important for?

Answer 6

angular acceleration in ( rotational direction)

Question 7

what is the utrical and saccular detection system used for?

Answer 7

inertial guidance detectors and detectors of gravity

Question 8

what do the sacculus and the utricle striola separate?

Answer 8

hair cells with opposite polarity

Question 9

how is the saccculus directed

Answer 9

VERTICALLY

Question 10

how is the utricle directed?

Answer 10

horizontally

Question 11

the ________ of a group of hair cells located on the same side and are in the same orientation

Answer 11

kinocilia

Question 12

the ampulla of each canal are oriented in _________?

Answer 12

the same direction

Question 13

why is there continuous representation of all body movements?

Answer 13

because there are structures on both sides of the head

Question 14

in the utricle and the sacculus the cilia of the hair project into the _________ _________ _________

Answer 14

gelatinous otolithic membrane

Question 15

the mecahnism for stimulating hair cells differs btw __________ vs ___________ and ___________

Answer 15

ampulla vs. the utricle and the sacculus

Question 16

what is the otoconia?

Answer 16

a calcium carbonate covering which provides mass to cover the membrane

Question 17

*when you are accelerating forward what is the displacement of the otolithic membrane and hair cells? and what type of polarization is this?prob on test see pg 914

Answer 17

backward

depolarization( i.e. increasing response of innervating CN8 -excitation)

Question 18

*when you are decelerating what is the displacement of the otolithic membrane and hair cells? and what type of polarization is this? prob on test see pg 914

Answer 18

forward

hyperpolarization (i.e. decreasing response of innervating CN8 -inhibition)

Question 19

forces acting on the head and the displacement of the otolithic membrane will __________ or ___________ sets of hair cells

Answer 19

excite or inhibit

Question 20

* the displacement of the otolithic membrane and hair cells is in the _________ direction of the _______force prob on test

Answer 20

the opposite direction of the inertial force

Question 21

how many degree of rotation do we detect?

Answer 21

three ( i.e. 3 axis: yaw ( z axis), roll (x axis), pitch( y axis) see p6 916

Question 22

which canals on either of the head work together?

Answer 22

the anterior canal on one side works with the posterior canal of the other side

Question 23

explain the mechanism of how the anterior canal on one side works with the posterior canal of the other side

Answer 23

rotation in a particular direction will yield excitation of the hair cells in one canal of a pair and inhibition in the other

Question 24

the semicircular canal is filled with?

Answer 24

fluid

Question 25

what membrane is displaced by the inertia of the fluid in the canals?

Answer 25

the cupula

Question 26

fluid flow and angular acceleration are in the _______ direction

Answer 26

opposite

Question 27

when you move your head to the right what happens to the vestibular nerve on the right and what happens to the one on the left

Answer 27

the one on the right is excited ( depolarized) and the one on the left is inhibited ( hyperpolarized)

Question 28

explain the vestibular ocular reflex with and example of turning to the left

Answer 28

the left vestibular nuclei is excited while the left is inhibited–> the left vestibular nuclei excites the right abducens and via the mlf the left CN III is excited and the eyes turn right , the inhibition o of the left vestibular nuclei inhibits the left abducens and right CN III

Question 29

why does nystagmus result in pathological conditions

Answer 29

the brain can mistake the resting discharge as representing a head movement

e.g. if there is no firing from the left canal and there is baseline firing in the right canal there will be a right nystagmus ( named for the resetting of the saccade) because it mimicks rotation to the right i.e. a slow movement of eyes to the left ( as in a normal rotation to the right) and a snap back to the right quickly

Question 30

if a person has no firing in the right ear which way would they fal if they try to get up from their seat and why ?

Answer 30

they would fall the right

the pathology mimicks a rotation to left so the person thinks they are falling left and they will excite their extensor muscles to compensate and maintain posture which disrupts balance