06a: Peripheral Vestibular System

Question 1

The vestibular receptors are actually (X).

Answer 1

X = hair cells

Question 2

Where are the vestibular receptors located?

Answer 2

1. Semicircular canals

2. Utricle and saccule (maculae)

Question 3

Vestibular nuclei send axons to:

Answer 3

1. Cerebellum
2. Extra-ocular muscle nuclei
3. Reticular formation
4. SC

Question 4

Vestibular receptors are divided into which groups?

Answer 4

1. Static receptors

2. Kinetic receptors

Question 5

List the (X) vestibular receptors, which respond to linear accelerations.

Answer 5

X = static

Maculae of the utricle and saccule

Question 6

List the (X) vestibular receptors, which respond to angular accelerations.

Answer 6

X = kinetic

Cristae of semicircular canals

Question 7

Which vestibular receptors play prominent role in signaling static position of head?

Answer 7

Static receptors

Question 8

Which vestibular receptors play prominent role in signaling angular velocity of (rotating) head?

Answer 8

Kinetic receptors

Question 9

List the three major functions of the vestibular system.

Answer 9

1. Subjective sensation of motion/spatial orientation
2. Postural control
3. Stabilizing eyes during head movement

Question 10

T/F: Most of vestibular system’s actions are reflexive (occur at unconscious level).

Answer 10

True

Question 11

T/F: Our perception of spatial orientation is essentially completely dependent on vestibular input.

Answer 11

False

Question 12

T/F: At rest, vestibular primary afferents discharge action potentials.

Answer 12

True

Question 13

Bending of (X) toward kinocilium causes (Y). And away causes (Z).

Answer 13

X = sterocilia;
Y = depolarization of HCs
Z = hyper-polarization of HCs

Question 14

Bending of (X) toward kinocilium is associated with (increase/decrease) in firing frequency of (Y).

Answer 14

X = sterocilia;
Increase;
Y = primary afferent fibers

Question 15

The amplitude of depolarization/hyperpolarization of hair cells depends on:

Answer 15

Direction of bending of cilia, relative to kinocilium

Question 16

Bending of cilia perpendicular to kinocilium will (depolarize/hyperpolarize) HC.

Answer 16

Neither - no change in HC voltage if perpendicular

Question 17

In the (X), the macula is approximately horizontal when body is upright. And in the (Y), it’s vertical.

Answer 17

X = utricle;
Y = saccule

Question 18

In the otolith organs, the cilia are embedded in (X) containing (Y) called “otoconia”.

Answer 18

X = gelatinous material (otolithic membrane)
Y = CaCO3 crystals

Question 19

Otoconia function in bending motion.

Answer 19

Make otoliths denser than endolymph, causing Otolithic membrane (and cilia of HCs) to sag

Question 20

Otoconia function in linear acceleration.

Answer 20

Heavier otoliths lag behind (due to inertia), bending cilia of HCs

Question 21

Degree of tilt/head movement is indicated by (X).

Answer 21

X = frequency of firing of primary afferents

Question 22

The direction of movement is indicated by (X).

Answer 22

X = which primary afferents (or HCs) are active

Question 23

The magnitude of head movement is indicated by:

Answer 23

Change in rate of firing of primary afferent fibers

Question 24

In semicircular canals, the HCs are embedded in (X), which extends into the (Y) fluid that fills the canals.

Answer 24

X = cupula (gelatinous material)
Y = endolymph

Question 25

Why (does/doesn't) the cupola move with respect to the (X) during linear acceleration?

Answer 25

Doesn't; X = semicircular canal; Same specific gravity as endolymph that fills canal

Question 26

Movement of endolymph in (X) causes (Y) to swing like a door.

Answer 26

``` X = semicircular canal; Y = cupula ```

Question 27

On each side of the head, there are (X) number of semicircular canals, all (parallel/perpendicular) to each other. List them.

Answer 27

X = 3; perpendicular; Horizontal, anterior, posterior

Question 28

List the complimentary pairs of the semicircular canals.

Answer 28

1. L and R horizontal 2. L posterior with R anterior 3. R posterior with L anterior

Question 29

Horizontal semicircular canals are perfectly horizontal if head is in which position?

Answer 29

Tilted forward 30 degrees

Question 30

Depolarization of hair cells is due to (X) ion moving down (chemical/electrical) gradient from (Y) space to (Z) space.

Answer 30

X = K+ Electrical; Y = endolymph Z = HC

Question 31

Endolymph has high concentration of (X) ions and low concentration of (Y) ions. What's the typical potential (in mV) of this space?

Answer 31

``` X = K+ Y = Na and Ca ``` +80 mV

Question 32

The (X) membrane separates the endolymph from the (Y).

Answer 32

``` X = reticular Y = perilymph ```

Question 33

Perilymph has high concentration of (X) ions and low concentration of (Y) ions. What's the typical potential (in mV) of this space?

Answer 33

``` X = Na Y = K ``` 0 mV

Question 34

The hair cells have high concentration of (X) ions and low concentration of (Y) ions. What's the typical potential (in mV) of this space?

Answer 34

``` X = K Y = Na ``` -40 mV

Question 35

In any one semicircular canal, how do the HCs differ in orientation?

Answer 35

They don't! Identical orientation

Question 36

Saccule respons best to movements in which plane?

Answer 36

Saggital (front/back movement)

Question 37

Utricle respons best to movements in which plane?

Answer 37

Frontal (L/R movement)

Question 38

The striola is present in (otolith organs/semicircular canals) and functions to:

Answer 38

Otolith organs; Divides hair cells into two populations with opposite polarities

Question 39

The macula of the otolith organs is analogous to (X) of semicircular canal. Define these.

Answer 39

X = Crista; Sensory epithelium that contains the hair cells

Question 40

Semicircular canals respond only to which type of movement?

Answer 40

Changes in velocity (angular acceleration)

Question 41

You turn your head to the right, primarily activating (X) vestibular structures. Describe direction of fluid flow.

Answer 41

X = horizontal semicircular canals; R: toward ampulla L: away from ampulla

Question 42

You turn your head to the right. Where does the de/hyper-polarization happen?

Answer 42

Depolarization in R horizontal semicircular canal. Hyperpolarization in L canal.

Question 43

T/F: Difference in response of semicircular canal pairs is due to opposite orientation of hair cells and kinocilium between the pairs.

Answer 43

False - due to opposite movement of fluid within canal pairs

Question 44

Pressure exerted by fluid on cupula is in the (same/opposite) direction as the head rotation.

Answer 44

Opposite