vestibular system

Question 1

old dogs can suffer a ____ problem with their vestibular system

Answer 1

temporary

Question 2

vestibular disease sudden onset of symptoms

Answer 2

twisting and rolling on the ground as if terminally confused; eyes move rapidly back and forth (nystagmus)

Question 3

the vestibular system

Answer 3

• monitors the position and movement of the head
• gives us our sense of balance and equilibrium
• helps coordinate movements of the head and eyes
• coordinates adjustments to body posture

Question 4

what happens when the vestibular system is disrupted

Answer 4

• unpleasant, stomach turning feelings we associate with motion sickness (vertigo and vomiting)
• disequilibrium
• uncontrollable eye movements

Question 5

vestibular labyrinth

Answer 5

within bony labyrinth of inner ear

Question 6

otolith organs

Answer 6

utricle, saccule

• detect linear acceleration of head
• head tilt
• gravity is a linear acceleration
• otoliths detect tilt of head relative to gravity

Question 7

3 semicircular canals

Answer 7

• sensitive to head rotation
• angular acceleration of head

Question 8

these sensory functions are carried out by ____ cells, which communicate with axons of the vestibular portion of the 8th nerve, whose cell bodies lie in ____ ____

Answer 8

hair; scarpa’s ganglion

Question 9

all bodies moving in three dimensions have six degrees of freedom:

Answer 9

3 translational and 3 rotational

Question 10

otoliths: utricle and saccule

axes

Answer 10

• detect linear accelerations along the 3 translational axes: x, y, x
• static head tilts relative to direction of the force of gravity

Question 11

kinocilium

Answer 11

tallest stereocilia

Question 12

movement of the ____ toward the ____ opens mechanically gated channels and depolarizes it

Answer 12

stereocilia; kinocilium

Question 13

movement away from the kinocilium ____ the cell

Answer 13

hyperpolarizes

Question 14

vestibular hair cells are located in the ____ and the ____ and in 3 juglike swellings called ____ in the base of the semicircular canals

Answer 14

utricle; saccule; amupllae

Question 15

arrows indicate direction of ____ deflection

Answer 15

depolarizing

Question 16

utricle and saccule detect ____ ____ and ____ ____ of the head induced by tilting or translational movements of the head

Answer 16

static displacements; linear accelerations

Question 17

what is the macula

Answer 17

the sensory epithelium consisting of hair cells and supporting cells

Question 18

hair bundles are within a ____ ____ which is covered by ____

Answer 18

gelatinous layer; otoconia

Question 19

what do otoconia do to the otolithic membrane

Answer 19

make it heavier than fluids around it

Question 20

when head tilts gravity causes ____ ____ to shift relative to sensory epitheloum

Answer 20

otolithic membrane

Question 21

what does shearing cause

Answer 21

displacement of hair cell bundles and a receptor potential in hair cell

Question 22

during linear accelerations of the head there is also a “shearing” motion betwen the ____ ____ and the ____ ____

Answer 22

sensory epithelium; otolithic membrane

Question 23

the greater mass of the ____ ____ causes it to temporarily lag behind the ____ ____, leading to transient displacement of hair cell bundle

Answer 23

otolithic membrane; sensory epithelium

Question 24

hair cell response is

linear acceleration

Answer 24

transient

Question 25

during static tilt hair cell response is

Answer 25

sustained | constant acceleration due to gravity

Question 26

what type of response is of the vestibular nerve axon from an otolith organ to forward and backward changes in head tilt

Answer 26

sustained response

Question 27

what type of response is of the vestibular nerve axon from an otolith organ to forward and backward acceleration of the head

Answer 27

transient response

Question 28

hair cells on opposite sides of the ____ have opposing directional polarities

Answer 28

striola

Question 29

what organs are responsive to head displacements on all directions

Answer 29

otolithic

Question 30

utricle is mainly concerned with motion in the ____ plane

Answer 30

horizontal

Question 31

saccule mainly concerned with motion in the ____ plane

Answer 31

vertical

Question 32

at the base of each semicircular canal is a bulbous expansion called the

Answer 32

ampulla

Question 33

within the ampulla is the sensory epitheloum called the ____ that contains the hair cells

Answer 33

crista

Question 34

the hair bundles of the ampulla extend into a gelatinous mass called the

Answer 34

cupula

Question 35

how is the cupula distorted by movements of the endolymphatic fluid

Answer 35

when the head turns in the plane of one of the semicircular canals, the **inertia** of the endolymph produces a **force** across the cupula, moving it away from the direction of head movement and causing displacement of the hair bulbs

Question 36

when cupula moves in the appropriate direction, all the hair cells are

Answer 36

depolarized

Question 37

when the cupula moves in the opposite direction all the hair cells are

Answer 37

hyperpolarized

Question 38

head rotation moves the cupula in opposite directions for the two partners, resulting in:

Answer 38

opposite changes in their firing rates

Question 39

what is angular acceleration

Answer 39

transient response of vestibular nerve axon from left and right horizontal semicirculat canals to left rotation of the head

Question 40

hair cells in the left horizontal canal ____ when the head turns left

Answer 40

depolarize

Question 41

hair cells in the right horizontal canal ____ when the head turns left

Answer 41

hyperpolarize

Question 42

what are the 3 reflexes of central pathways for stabilizing gaze, head and posture

Answer 42

* maintain equilibrium and gaze during movement * maintain posture and balance * maintain mucle tone

Question 43

lateral vestibulospinal tract

Answer 43

* ipsilateral forelimb and hindlimb extensors * balance

Question 44

medial vestibulospinal tract

Answer 44

bilateral to motor neurons for neck

Question 45

vestibulo-ocular reflex (VOR)

Answer 45

head rotation activates semicircular canals in inner ear and drives **compensatory eye movements to stabilize image** of visual world on the retina

Question 46

optokinetic nystagmus

Answer 46

induced by looking at moving visual stimuli, such as moving horizontal or vertical lines, and/or sripes

Question 47

postrotatory nystagmus

Answer 47

if one spins in a chair continuously and stops suddently, the fast phase of nystagmus is in the opposite direction of rotation, known as the "post-rotatory nystagmus", while slow phase in in the direction of rotation

Question 48

pathologic nystagmus

Answer 48

damage to one or more components of the vestibular system - **labyrinthitis or vestibulitis or vestibular disease**