Motor Control 4

Question 1

What does the Vestibular system do?

Answer 1

Process sensory information related to head position, spatial orientation (with respect to gravity) and movement

Question 2

What is the vestibular bony ‘labyrinth?

Answer 2

Part of the vestibular system responsible for balance and the position of the body in space

Question 3

Where is the bony labyrinth found?

Answer 3

In the temporal bone

Question 4

What is perilymph?

Answer 4

The substance that separates the membranous labyrinth from the bony labyrinth

Question 5

What is endolymph?

Answer 5

The liquid inside the bony labyrinth

Question 6

What is the structure of the labyrinth in the inner ear?

Answer 6

3 semicircular canals (anterior, posterior, lateral), positioned in line with each plane of movement

Question 7

What plane is the anterior semi-circular canal in?

Answer 7

Frontal plane

Question 8

What plane is the posterior semi-circular canal in?

Answer 8

Saggital Plane

Question 9

What plane is the lateral semi-circular canal in?

Answer 9

Transverse Plane

Question 10

What is the name of the enlarged section of each semicircular canal where it connects with the Utricle?

Answer 10

Ampullae

Question 11

What is located within the Ampullae?

Answer 11

The Crista Ampullaris

Question 12

What does the cupula around the crista ampullaris do?

Answer 12

It deforms due to angular acceleration of the head which stimulates hair cells in the crista ampullaris which sends signals to the brain to detect angular head motion

Question 13

What is the crista ampullaris?

Answer 13

A cone shaped structure in the ampullae covered in hair cells that detect angular acceleration

Question 14

What are the 5 sensory organs of the Labyrinth?

Answer 14

3 Semicircular canals

2 Otolith Organs (Utricle and Saccule)

Question 15

What is kinocilium and stereocilia?

Answer 15

Kinocilium: Longer hairs on the hair cell
Stereocilia: The shorter hairs of the hair cells

Question 16

What occurs if the kinocilium deflects towards the stereocilia?

Answer 16

Decrease of firing rate/hyperpolarisation

Question 17

What occurs if stereocilia deflect towards the kinocilium

Answer 17

Increase in firing rate/depolarisation

Question 18

If you angularly accelerate in one direction, what direction will the endolymph move in as you accelerate?

Answer 18

the other direction

Question 19

If you angularly accelerate in one direction, what direction will the endolymph move in once you start to decelerate?

Answer 19

The same direction as you moved

Question 20

How does activity of one semicircular canal affect the other?

Answer 20

It inhibits the opposite side

Question 21

If the head accelerates in a counterclockwise direction, explain what will happen in the semicircular canals of both sides of the head

Answer 21

Endolymph will travel clockwise, which will cause depolarisation/increased firing rate of the left side, and hyperpolarisation/decreased firing rate on right side. Both will send excitatory signals to their own side and inhibitory signals to the opposite side, but as the right side is decreased firing rate, it does not inhibit the left side much, but the left side does inhibitthe right side a lot

Question 22

What is the macula?

Answer 22

A patch of the epithelium of the utricle and saccule that has hair cells on it

Question 23

How are the hair cells orientated on the macula?

Answer 23

They are not all in the same direction.

Question 24

What can (the hair cells on) the macula detect?

Answer 24

Head tilt and linear acceleration, and position with respect to gravity

Question 25

Where are the saccule and utricle found?

Answer 25

In the vestibule

Question 26

how do the hair cells on the macula of the utricle/saccule detect head tilt?

Answer 26

Otolith crystals that sit on top of them will be affected by gravity when the body accelerates linearly or tilts, shifting the hair cells and affecting the firing rate

Question 27

What is relationship between strength and length of stimulus, and the response?

Answer 27

Stronger stimulus leads to stronger response with shorter latency
Longer stimulus means longer response

Question 28

What are the two ways higher levels of the brain can modulate reflex mechanisms?

Answer 28

Reflex suppression (raises threshold for reflex excitation)
Reflex Potentiation (lowers the threshold for reflex excitation)