Lecture 23

Question 1

What is the role of the vestibular system?

Answer 1

it provides the brain with information about head movement and location`

Question 2

What does the vestibular system detect? (what is it stimulated by)

Answer 2

Angular and linear accelerations of the head

Question 3

What is acceleration?

Answer 3

Rate of change of velocity

Question 4

What is linear acceleration of the head?

Answer 4

Head movements with respect to gravity, body is moving backwards and forwards

Question 5

What is angular acceleration of the head?

Answer 5

Movements of the head (e.g. nodding, stretching)

Question 6

What does the vestibular system do in response to the stimuli?

Answer 6

• generates reflexes to compensate for head movement and the perception of movement in space
• provides information to help with maintain of right posture
• provides information for conscious awareness of position/movement/acceleration of the head and body

Question 7

What are the two parts of the vestibular system?

Answer 7

1. semi-circular canals

2. otolith organs

Question 8

Where is the vestibular system located?

Answer 8

in the inner ear.

Question 9

What are the semi-circular canals?

Answer 9

They are canals sensitive to angular acceleration during head rotation. they work in pairs, one set in each ear. the canals are aligned in three axes, each canal is most vigorously stimulated by acceleration in its performed plane.

Question 10

what are the semi-circular canal filled with?

Answer 10

endolymph

Question 11

What plane is the horizontal canal stimulated by?

Answer 11

Transverse plane (crossing a road)

Question 12

What plane is the anterior canal stimulated by?

Answer 12

sagittal (nodding)

Question 13

What plane is the posterior canal stimulated by?

Answer 13

coronal (head tilting)

Question 14

What is the ampulla?

Answer 14

a structure at the bottom of the semi-circular canal where there are hair cells.

Question 15

What is the structure of the ampulla?

Answer 15

There are hair cells, which from project cilia out to the duct of the semi-circular canal (lumen). The cilia sit in a structure called the cupula.

Question 16

What is the effect of the ampulla’s structure on fluid movement?

Answer 16

fluid cannot move very freely

Question 17

how does inertia occur in the cupula?

Answer 17

When the head moves, the fluid stays for a second longer before catching up with the movement. this causes inertia, which results in the cilia bending.

Question 18

What does resting discharge rate mean?

Answer 18

It means that vestibular hair cells can detect movement in two directions

Question 19

How does transduction occur in the vestibular system?

Answer 19

When head movement cause the bending of the longest hairs in the cupula, mechanically gated ion channels on the cilia open. this results in an influx of potassium, depolarising the cell. this leads to opening of voltage gated calcium channels, so there is an influx of calcium. there is release of neurotransmitter, and an increased firing rate.
if the hairs bend towards the short stereo cilia, the mechanically gated ion channels close.

Question 20

What are the Otolith organs?

Answer 20

they are the utricle and the saccule, and they detect linear acceleration.

Question 21

How is the Utricle structured?

Answer 21

It is approximately horizontal when standing (hair cells within it are oriented vertically)

Question 22

How id the Saccule structured?

Answer 22

it is approximately vertical when standing (hair cells within it are oriented horizontally)

Question 23

What is the anatomy of the otolith organs?

Answer 23

They have hair cells which sit inside a structure called the macula.
the otoconia is small stores of CaCo3, and it acts as wights on the otolith organs to prevent them from shifting too quickly.

Question 24

Where are EPSPs transmitted from the otolith organs?

Answer 24

to the vestibular nuclei in the brainstem

Question 25

What is the information from the vestibular system used for?

Answer 25

• stabilise eyes
• stabilise the head
• maintain balance

Question 26

What is Vertigo?

Answer 26

Is it motion sickness (illusion of movement and dizziness) cause by disease affecting the vestibule or its afferent fibers

Question 27

what is motion sickness?

Answer 27

it is caused by mismatch between visual and vestibular information

Question 28

what can help motion sickness?

Answer 28

sea leg tablets - Meclozine Hydrochloride

Question 29

What are bedspins?

Answer 29

It is motion sickness caused by alcohol. Ethanol infiltrates cupula, lower density and causes it to ‘float’, bending hairs on hair cells and creating perception of movement

Question 30

What are ototoxic drugs?

Answer 30

they are medications which are harmful to hair cells (over 600). can result in temporary to permanent loss of hearing and balance.