Vestibular System

Question 1

3 Kinds of Mechanics

Answer 1

Macromechanics - turning head and making fluid move
Micromechanics - hair cells move
Nanomechanics - molecular gates open

Question 2

3 Semicircular Canals

Answer 2

Lateral for horizontal, and anterior and posterior for vertical

Question 3

Movement Transduction to Hair Cells (3 special terms)

Answer 3

Ampulla is widened section w/ crista coming up (ridge on floor with hair cells). Hairs project into gelatinous cupula. Endolymph movement causes cupula to move, deflecting hair cells

Question 4

Lymph Different Concs

Answer 4

Endo: Low Na/High K
Peri: High Na, Low K like CSF.
Gradient allows hairs to function and depol

Question 5

Alcohol Vestib Effects

Answer 5

Makes cupula less dense than endolymph, leading to stimulation in one direction. Hair cells don’t adapt so effects continue until alcohol wears off

Question 6

2 Structural Types of Hair Cells

Answer 6

Type I (Calyx Type) - aff comes in and forms calyx around cell, eff synapses onto calyx
Type II - aff and eff each synapse on hair cell

Question 7

3 Reflexes of Vestibular Signals

Answer 7

Vestibulo-ocular - eyes in head
Vestibulo-collic - head on trunk
Vestibulo-spinal - trunk on ground

Question 8

Vestibulo-ocular Reflex

Answer 8

Turning head right excites R horizontal canal and inhibits L, so R sends excitatory signals to R vestibular nucleus which decussates and excites abducens nucleus, exciting L IV and R III to turn eyes left. L horizontal does opposite everything inhibitorily

Question 9

2 Components of Nystagmus

Answer 9

Slow: Labyrinthine component
Fast: Corrective component, CNS

Question 10

2 Sources of Peripheral Vestibular Hypofunction

Answer 10

Loss of unilateral function (like trauma) loses resting activity of ipsilateral nerve and nuclei and difference is interpreted as motion -> nystagus
Benign paroxysmal positional vertigo (BPPV) means loose ooconia bouncing around, any motion relating to gravity causes nystagmus

Question 11

Caloric Test

Answer 11

Water 7 deg above or below body temp injected into ear, eyes should deviate towards the cold side

Question 12

VCR Test

Answer 12

Vestibulo-collic reflex, play loud noise to stimulate utricle/saccular shit to test otolinth function

Question 13

Meniere’s Disease

Answer 13

Endolymph fluid imbalance leads to bulging of membranous labyrinth, causing tinnitus/veritgo/hearing loss. Treat by trying to get water out, maybe gentamicin injections

Question 14

Superior Canal Dehiscence

Answer 14

Hole in osseous labyrinth over semicircular canal exposes membranous canal to sound and pressure stimuli