Lec 13

Question 1

when you rotate you head left, what happens to firing rate of ampullae in left and right lateral canals

Answer 1

Left - since kino oriented inwards and sterio outwards, move head left moves fluid right, causing increase in firing rate of hair cells in left ampulla.

right - by same logic, right decrease firing rate.

Question 2

describe how the otolith organs work

which does what?

Answer 2

hair cells in macula have cilia embedded in an otolithic membrane

calcium carbonate crystals are embedded on top of
gelatinous membrane that cause a sheering movement in the membrane affecting the cilia

Utricle faces up (horizontal accel) sterio point away from the striola

Saccule faces sideways (vertical accel) sterio point towards the striola

Question 3

vestibular afferents have cell bodies in __. Axons travel via the ___ nerve

Answer 3

vestibular ganglion

vestibulo-cochlear nerve (CN VIII)

Question 4

What are the vestibular nuclei to know (4)

and corresponding tracts

Answer 4

Lateral vest nuc (LVN) - lat vestspin tract

Medial vest nuc (MVN) - medial vestspin tract

Sup vest nuc (SVN) -

Inf vest nuc (IVN)

Question 5

The SVN and MVN project to the ___ to the __(3)_.

This controls what?

Answer 5

Medial longitudinal fasciculus (MLF)

Oculo-motor nucleus

trochlear nucleus

abducens nucleus

controls eye muscles/reflexes. (VOR)

Question 6

what purpose vestibulo occular reflex serve and mechanism.

Answer 6

allow to keep eye on target when moving actively or passively.

pulls eyes in opp direction of head movement.

rot head = move fluid = sereocillia move towards or away from kino = firing rate change = go to path that pulls eyes

*Which pathway?

at same time, opposite eye does same thing.

Question 7

what does continuous vestibular stimulus lead to in eyes

Answer 7

nystagmus

fluid keep moving when dizzy or damaged cause vest occ ref

direction of nystagmus refers to fast phase of mvmnt

Question 8

names some tests for normal nysatagmus (3)

what does COWS mean?

Answer 8

rotating chair test - rotate chair and see if eye does nystagmus after some rotating - tests horizontal canal

head impulse test - tests all planes - record eye movement while doctor rapidly jerk head

caloric irrigation test (is the gold standard test) - use cool and hot water to create rotation of endolymph fluid in horizontal canal
- cool in right ear cause fluid to sink and cause left nystagmus (clockwise fluid movement)

COWS = cold - opposite, warm - same