7. Special senses: balance

Question 1

Vestibule has 2 otolith containing organs, name them?

Answer 1

– Saccule macula (continuous with cochlea)

– Utricle macula (continuous with semi-circular canals)

Question 2

What monitors vertical movement of head?

Answer 2

Saccule maculae (s for sky)

Patch of hair/supporting cells on the vertical wall of saccule

Question 3

Monitor position of head relative to force of _______

Answer 3

Monitor position of head relative to force of gravity

Question 4

What monitors horizontal movement?

Answer 4

Utricle maculae

Patch of hair/supporting cells on the horizontal wall of utricue

Question 5

What are the 3 canals of the semicircular canals (aka labyrinths)?

Answer 5

Posterior
Horizontal
Anterior

Question 6

Hair cells, project hairs into an ________ (ear stone) containing gelatinous structure.

Answer 6

Hair cells, project hairs into an otolithic (ear stone) containing gelatinous structure.

Question 7

Role of cilia and kinocilium

Answer 7

Provide directional info

Found in the saccule and utricle.
Movement of the otolithic membrane (from tilting or translational movement) bends the cilia/kinocilium in a specific direction. This opens the hair cell cation channels

Question 8

What is the organisation of the otolithic hair cells?

Answer 8

2 types of organisation:
1. Vertical
2. Horizontal
With the hair cell base supported in an area of supporting cells. These cells are called the “macula”

Question 9

Difference between kinocillia and steriocillia of hair cell?

Answer 9

Kinocillia = fat end
Steriocillia = thin end

Question 10

When the hair cells bend TOWARDS the kinocillium…

Answer 10

Results in depolarisation

• -> Increased impulse freq
• -> Excitation

Bc channels are being opened due to tip links

Question 11

When the hair cells bend AWAY the kinocillium…

Answer 11

Hyperpolarisation

• ->Decreased impulse freq
• -> Inhibition

Question 12

How is rotational deceleration/acceleration measured?

Answer 12

In the SEMI-CIRCULAR CANALS

Three planes of orientation

Within each canal is a semi-circular duct. In the duct there is an ampulla.

Ampulla contents: Supporting cells, hair cells, cilia, kinocilium, cupula, crista ampullaris

Question 13

Rotation directions are designated as _____ _____ + _____

Answer 13

Rotation directions are designated as Roll Pitch and Yaw

Roll = Rotation of face around nose (x) axis
Pitch= Rotation around y axis, looking up and down
Yaw= Rotation around z axis, looking side to side

Question 14

What causes movement of the cupula?

Answer 14

Endolymph movement in the semicircular canal

Question 15

What is the process of monitoring dynamic equilibirum?

Answer 15

Measuring change sin rotation:

1. Signal transduction leads to resting rate of transmitter release
2. Bending in one direction (towards the kinocilium) – depolarisation and ↑AP rate
3. Other direction – hyperpolarisation and ↓AP rate

So… one side of head depolarises; other hyperpolarises

Question 16

Difference in the rotational signals detected in the R and L head?

Answer 16

Turning motion towards side X leads to increased firing at side X.
Decreased firing at contralateral side.

Question 17

What causes Meniere’s disease?

E.g. Vertigo, nausea, tinnitus and hearing loss

Answer 17

Build up of the endolymph that baths the vestibular apparatus
Normally drains to venous sinus

Question 18

The information from the vestibular apparatus goes to cerebellum and brainstem. Integration with other info from visual receptor + somatic receptors + reticular nuclei, it is used to..

Answer 18

– Control eye muscles via oculomotor control
– Maintain you in an upright position via spinal motor control
– Be aware of body position and acceleration

Question 19

What is the purpose of the caloric test?

Answer 19

Tests condition of brainstem in comatose patients

Question 20

What is the process of the caloric test?

Answer 20

Putting warm water in the external meatus of a patient sets up calorically induced movements in the labyrinth system.

Question 21

What does the warm water in the caloric test mimic?

Answer 21

Movement of head of supine patient with head at 30 degrees from horizontal mimics left/ right movement of the head.
Warm water mimics moving head towards the irrigated ear

Question 22

Comparison is use of cold and hot water in the caloric test?

Answer 22

Cold water does the opposite (COWS Cold Opposite Warm Same)

Question 23

What is the nystagmus pattern for a movement towards the irrigated ear?

Answer 23

Nystagmus pattern for a movement towards the irrigated ear is slow away from
direction of rotation and a fast return in same direction of rotation

Question 24

When looking for a nystagmus pattern towards irrigated ear, what is found in comatose patients?

Answer 24

In comatose patients there is no fast saccade, only the slow component.

Question 25

When looking for a nystagmus pattern towards irrigated ear, what is found in patients damage to one of semicircular canal?

Answer 25

Spontaneous nystagmus occurs when one side of the patients system has damage to one of the semi-circular canals.

Question 26

Role of ololith?

Answer 26

Add weight to enhances sense of gravity and motion
They are calcium carbonate protein granules.
Positioned on top of the otolithic membrane