Vestibular system

Question 1

What is the vestibular system involved with?

Answer 1

• Balance, and knowing where you are in space
• Linear and angular acceleration
• Eye reflexs

Question 2

What does that ampulla and utricle and sacule measure? (structure of these organs)

Answer 2

Ampulla - has cristae ampularis, and measures angular acceleration
-cristae ampularis - has sensory cells sitting with cupula on top - all these sensory cells are polarised in the same direction

Utricle and saccule - will detect static head position in relation to gravity and linear acceleration
-sterocilia project into ortholitic membrane , has otoconia on top (calcium carbonate cyrstals) - have weight

Hair cells in the vestibular system are polarised and all lined up in the same direction

Question 3

How does the vestibular system work

Answer 3

At rest - have a constant discharge rate of cells

• Depolarisaiton - move towards kinocilia, increased firing and vice versa
• the cristae ampularis cells - wif they have increased firign (depolarisatin) then will take this as an acceleration in this direction , then if you start to spin around then will get a constant velocity and then motion is no longer percieved

Question 4

How do you get vertigo from damage to ear?

Answer 4

At rest - right and left side of ear will fire at same rate
-However if get damage to one side of the ear, then will get less firing and this is sensed as movement when you are actually standing still

Question 5

Vestibular ocular reflex

Answer 5

3 nerves that go to the muscles
-When turn to one side, then one side will fire more than the other
-very quick reflex causes your eyes to turn to the opposite side at the same speed as head has moved so that you can keep your vision straight
(Move head left - move eyes to right)

Question 6

What is a nystagmus

-What happens when there is reduce function in right ear?

Answer 6

Rhythmic oscillation of the eyes with a fast and slow phase

• is described in the direction of the fast phase
• Hypofunction (e.g cold water) in right ear, (or hyperfunction in left ear (warm)- normally not the case) - then will have a nystagmus to the left (COWS)

Question 7

Head thurst

Answer 7

Move head, eyes should stay straight at nose

-Abnormal - eyes will move when head does then look towards center again - reflex damage - defect there

Question 8

BPPV - benign paroxysmal positional vertigo

What test is used

Answer 8

• vertigo for less than 1 min
• associated with certain positons
• due to debris in posterior semicircular canal

Dix Hallpike test - Go from a seated position to supine, - onset of vertigo, also look for nystagmus
-Is posterior semicircular canal

Eplys test - when put head off side of bed, and then will get them to move their head, and turn body