Vestibular System

Question 1

The vestibular system ____ us in space and tells us whether or not we are ____.

Answer 1

Orients

Moving

Question 2

The vestibular system, like the auditory system, is connected to the _____ nerve, or ____ ____ ____.

Answer 2

Vestibulocochlear nerve

Cranial nerve VIII

Question 3

How many semicircular canals does the vestibular system have? What are they called, and what is the difference between them?

Answer 3

3: superior, posterior, horizontal

Each is in a different orientation

Question 4

What does the ampullae contain and what is it attached to? In regards to the ampullae, what is the function of the semicircular canals?

Answer 4

Hair cells of semicircular canals, attached to semicircular canals
Semicircular canals provides greater space for endolymph to circulate in order to cause bending of hair cells in ampullae

Question 5

What are the names of the 2 otolith organs of the vestibular system?

Answer 5

Saccule

Utricle

Question 6

Yaw rotation corresponds to what type of movement and mostly activates what semicircular canal?

Answer 6

Spinning around

Horizontal

Question 7

Pitch rotation corresponds to what type of movement and mostly activates what semicircular canal?

Answer 7

Tilting head front or back

Superior canal

Question 8

Roll rotation corresponds to what type of movement and mostly activates what semicircular canal?

Answer 8

Tilting head left or right

Posterior canal

Question 9

In the ampulla, the hair cells are in the (same/different) orientation as one another.

Answer 9

Same

Question 10

In the otolith organs, the ____ divides them down the center. On either side of the division, the hair cells are oriented in the (same/opposite) directions as those across the division.

Answer 10

Striola

Opposite

Question 11

Because the hair cells of the otolith organs are oriented in opposite directions across the striola, some hair cells are ____ with a particular type of movement while others are ____.

Answer 11

Excited

Inhibited

Question 12

How is hair cell orientation of the utricle different from the saccule with regards to the striola?

Answer 12

Utricle: long stereocilia are oriented towards striola
Saccule: long stereocilia are oriented away from striola

Question 13

All hair cells on one side of the striola will have the same orientation of ____ to _____.

Answer 13

Longest

Shortest

Question 14

On top of the hair cells in the otolith organs is a gelatinous _____ layer topped with _____, which are essentially ____ ____ crystals. How does this layer affect hair cell bending upon head bending?

Answer 14

Endolymph
Otoconia
Calcium carbonate
Layer applies weight that causes bending of all hair cells in otolith organs upon bending of head and keeps them bent for duration of head bending

Question 15

Hair cells of otolith organs: head is tilted forward, hair cell is (excited/inhibited) and (returns to baseline before head is erected/ remains excited as long as head is tilted). When does the hair cell return to baseline? What happens to the hair cell when the head is tilted backwards?

Answer 15

Excited
Remains excited as long as head is tilted
Returns to baseline when head is no longer tilted
Hair cell is inhibited when head is tilted backwards

Question 16

Hair cells of otolith organs: forward acceleration mimics turning head (forward/backward). Does deceleration activate or inhibit hair cells?

Answer 16

Backward

Inhibit

Question 17

Each ampule has a grouping of hair cells in the (same/different) basic orientation. Are all the hair cells excited or inhibited by the same movement, or are only some?

Answer 17

Same

All are excited or inhibited by same movement

Question 18

In the ampula, sloshing of ____ on one side causes ____ on the other side to move, bending the hair cells towards the (shortest/longest).

Answer 18

Endolymph
Fluid
Longest

Question 19

The otolith organs sense ___ ___ and ___ acceleration.

Answer 19

Head tilt

Linear acceleration

Question 20

In the otolith organs, a hair cell that is excited by forward tilt is (excited/inhibited) by backward tilt. A hair cell on the other side of the striola from the first hair cell would be (excited/inhibited) by forward tilt and (excited/inhibited) by backward tilt.

Answer 20

Inhibited
Inhibited
Excited

Question 21

A ____ compartmentalizes the ampula and the semicircular canals so that sloshing of _____ on one side causes sloshing of the same fluid on the other side.

Answer 21

Membrane

Endolymph

Question 22

The hair cells of the ampula are excited when bent from (shortest to longest/ longest to shortest) and are inhibited when bent from (shortest to longest/ longest to shortest).

Answer 22

Shortest to longest

Longest to shortest

Question 23

The stereocilia of the ampullae respond to (change in head motion/ constant head motion/ both). How is this different from the otolith organs? Why?

Answer 23

Change in head motion only
Otolith organs can respond to change in head tilt as well as constant head tilt because the gelatinous endolymph and otoconia respond to gravity, keeping the hair cells bent as long as the head is bent

Question 24

Ampula hair cell firing with acceleration and deceleration: firing peaks when? What happens to firing when velocity is constant? When is the hair cell inhibited?

Answer 24

Firing peaks at start of acceleration
Velocity is constant: firing ceases
Inhibited at start of deceleration

Question 25

Semicircular canals sense direction and speed of _____ acceleration.

Answer 25

Angular

Question 26

True or false: both the otolith organs and semicircular canals respond to acceleration.

Answer 26

True

Question 27

The (otolith organs/ semicircular canals/ neither) respond to constant velocity. The (otolith organs/ semicirulcar canals/ neither) respond to constant head tilt.

Answer 27

Neither | Otolith organs

Question 28

The horizontal canals are most activated by shaking head (yes/no). The superior canals are most activated by shaking head (yes/no). The posterior canals are most activated by tilting head ___ or ____ (direction).

Answer 28

No Yes Left or right

Question 29

When turning the head to one side (left or right), the posterior or horizontal canals (depending on the type of motion) on the (same/opposite) side of motion are activated, whereas the posterior or horizontal canals on the (same/opposite) side of motion are inhibited. For instance, turning the head towards the right shoulder would activate the (left/right) horizontal canal while inhibiting the (left/right) horizontal canal.

Answer 29

Same Opposite Right Left

Question 30

The superior canals are most activated when the head is turned (forward/backward) and are most inhibited when the head is turned (forward/backward). The left and right superior canals are activated (at the same time/ at different times). Why?

Answer 30

Forward Backward At the same time Moving head forward and backwards doesn't involve left to right motion, so left and right superior canals are activated at the same time

Question 31

Rotating the body to the left (counterclockwise) while sitting on the center of a merry-go-round: which semicircular canals are activated, and on which side? Which side is inhibited?

Answer 31

Horizontal canals | Left is activated, right is inhibited

Question 32

Accelerating in a clockwise circle when driving onto a curved ramp: which semicircular canals are activated, and on which side? Which side is inhibited? Are any other parts of the vestibular system activated? If so, which ones and on which side(s)?

Answer 32

Horizontal canals Right is activated, left is inhibited Some hair cells in otolith organs are activated on both sides

Question 33

Nodding head forward to answer yes: which semicircular canals are activated, and on which side? Which side is inhibited? What happens when the head is returned to its upright position?

Answer 33

Superior canals Both sides are activated, neither side is inhibited Superior canals return to baseline

Question 34

The vestibular ocular reflex enables the ____ to readjust when the body is moving, as when walking. Without it, how would the world appear when walking?

Answer 34

Eyes | World would appear to bounce up and down

Question 35

Vestibular ocular reflex: In a normal conscious person, a head turn to one direction elicits first a (fast/slow) movement of the eyes to the (new direction/back to the original direction) and then a (fast/slow) movement of the eyes (to realign with the new head position/ refocus on the original focal spot). Which of these two eye movements only occurs when conscious?

Answer 35

``` Slow Back to the original direction Fast Realign with new head position Second (fast movement of eyes to realign with new head position) ```

Question 36

Vestibular ocular pathway (part 1): Information from one side of the body comes in through ____ ____ and makes 2 synapses in the ___ ____ ____ of the ____. One neuron crosses to the contralateral side of the brain and is (excitatory/inhibitory) and the other stays on the ipsilateral side of the brain and is (excitatory/inhibitory).

Answer 36

``` Scarpa's ganglion Medial vestibular nucleus Medulla Excitatory Inhibitory ```

Question 37

Vestibular ocular pathway (part 2): the information coming from the two neurons in the ___ ____ ____ is carried to the ____ ____ of the _____ and makes ___ more synapses there, leading to ___ total neurons synapsed upon.

Answer 37

``` Medial vestibular nucleus Abducens nucleus Pons 2 4 ```

Question 38

Vestibular ocular pathway (part 3): one neuron synapsed upon by the contralateral (excitatory/inhibitory) neuron in the ___ ___ synapses upon the (contralateral/ipsilateral) eye's ____ rectus, causing it to (contract/relax). The other neuron synapsed upon crosses over, becoming (contralateral/ipsilateral), then synapses in the _____ ____ and (activates/inhibits) the tract that goes to the (contralateral/ipsilateral) eye's ___ rectus, causing it to (contract/relax). The result is that the eyes move in the (contralateral/ipsilateral) direction as the head motion.

Answer 38

``` Excitatory Abducens nucleus Contralateral Lateral rectus Contract Ipsilateral Oculomotor nucleus Activates Ipsilateral Medial rectus Contract Contralateral ```

Question 39

Vestibular ocular pathway (part 3): one neuron synapsed upon by the ipsilateral (excitatory/inhibitory) neuron in the ___ ___ synapses upon the (contralateral/ipsilateral) eye's ____ rectus, causing it to (contract/relax). The other neuron synapsed upon crosses over, becoming (contralateral/ipsilateral), then synapses in the _____ ____ and (activates/inhibits) the tract that goes to the (contralateral/ipsilateral) eye's ___ rectus, causing it to (contract/relax). The result is that the eyes are prevented from moving in the (contralateral/ipsilateral) direction as the head motion.

Answer 39

``` Inhibitory Abducens nucleus Ipsilateral Lateral rectus Relax Contralateral Oculomotor nucleus Inhibits Contralateral Medial rectus Relax Ipsilateral ```

Question 40

Vestibular ocular reflex: when the head is turned left, the ____ horizontal canal is activated. The neuron that projects contralaterally from the medial vestibular nucleus to the abducens nucleus is (excitatory/inhibitory), and activating it causes contraction of the (left/right) lateral rectus and the (left/right) medial rectus. The neuron that projects ipsilaterally from the medial vestibular nucleus to the abducens nucleus is (excitatory/inhibitory), and activating it causes relaxation of the (left/right) lateral rectus and the (left/right) medial rectus. As a result, the eyes turn to the (left/right).

Answer 40

``` Left Excitatory Right lateral rectus Left medial rectus Inhibitory Left lateral rectus Right medial rectus Right ```

Question 41

When the medial rectus contracts, it makes the eyes move toward the (periphery/middle). When the lateral rectus contracts, it makes the eyes move towards the (periphery/middle).

Answer 41

Middle | Periphery

Question 42

Contraction of the left eye's medial rectus muscle will move the ___ eye to the ____.

Answer 42

Left eye | Right

Question 43

When the head is reclined at a 30 degree angle, the ___ canals are in the same plane as the table and the vestibular ocular reflex can be tested. Putting warm water in the ear mimics turning the head in the (same/opposite) direction as the ear that has the warm water, so the eyes turn to the (same/opposite) direction as the ear. Putting cold water in the ear mimics turning the head in the (same/opposite) direction as the ear that has the cold water, so the eyes turn in the (same/opposite) direction as the ear.

Answer 43

``` Horizontal Same Opposite Opposite Same ```

Question 44

In an unconscious person with no brain damage, would the person's eyes move rapidly back when testing the vestibular ocular reflex with water or would they stay in the same position? Why?

Answer 44

Stay in the same position | Fast movement of the eyes to realign with the new head position is disabled when the person is unconscious

Question 45

The ___ ____ ____ is the place in the midbrain is the place where crossing over of neurons occurs for wiring to the medial recti in the vestibular ocular pathway.

Answer 45

Medial longitudinal fasciculus

Question 46

Damage at the medial longitudinal fasciculus would affect the functioning of the (medial retcti/lateral recti) of each eye.

Answer 46

Medial recti

Question 47

Damage to the medial longitudinal fasciculus: putting cold water in the right ear, which mimics turning the head to the (left/right), would activate the (left/right) horiztonal canal. However, disruption of the signal telling the right medial rectus to (contract/relax) and the left medial rectus to (contract/relax) combined with the intact signals to the lateral recti means that the right eye would move (left/right/not at all) and the left eye would move (right/left/not at all).

Answer 47

``` Left Left Relax Contract Right Not at all ```

Question 48

Damage to the lower brainstem would cause the (ipsilateral/contralateral/both) pathways to be disrupted. What would be the result of putting cold water in the right ear?

Answer 48

Both | No movement of eyes

Question 49

When putting warm water into the right ear of a person with medial longitudinal fasciculus damage, only the ___ eye would move to the ____.

Answer 49

Left | Left