Test 2: lecture 18 balance

Question 1

problems with the vestibular system lead to __-

Answer 1

Unpleasant, stomach turning feelings we associate with motion sickness
– vertigo and vomiting

Disequilibrium

Uncontrollable eye movements

Question 2

___ can detect linear acceleration of the head

Answer 2

utricle and saccule (otolith organs)

Question 3

___detect tilt of head relative to gravity

Answer 3

otoliths (utricle and saccule)

linear acceleration and head tilt

Question 4

___ are sensitive to head rotation and acceleration

Answer 4

3 semicircular canals

Question 5

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

Answer 5

hair cells

Scarpa’s ganglion

Question 6

A ll bodies moving in three dimensions have six degrees of freedom:

Answer 6

3 translational and 3 rotational

Question 7

Otoliths utricle and saccule detect___ along the 3 translational axes, x,y, and z

Answer 7

linear accelerations

•Static head tilts relative to direction of the force of gravity

Question 8

semicircular canals detect ___ of the head

Answer 8

rotational or angular accelerations

Question 9

___ is the tallest stereocilia

Answer 9

kinocilium

Question 10

in the semicircular canals the CN 8 axons make up the ___

Answer 10

crista ampullaris

Question 11

in the otolithic organs (utricle and saccule) the Cn8 axons make up the ___

Answer 11

macula

Question 12

stereocilia of hair cells are held together by ___

Answer 12

tip links

Question 13

when the stereocilia move toward the kinocilium what happens?

Answer 13

depolarization

the endolymph has lots of K, movement toward the tallest opens the mechanically gated channels and K rushes in causing depolarization

Question 14

when the stereocilia move away from the kinocilium what happens

Answer 14

mechanically gated K channels close → hyperpolarization

Question 15

what is the fluid where the stereocilia sit?

Answer 15

endolymph

(has lots of K)

Question 16

Movement of the stereocilia ___ the kinocilium opens mechanically gated channels and depolarizes cell. Movement ___from the kinocilium hyperpolarizes the cell

Answer 16

toward

away

Question 17

Vestibular hair cells are located in the ___ and in three juglike swellings called ___ in the base of the semicircular canals

Answer 17

utricle and the saccule

ampullae

Question 18

direction of depolarization in the ampulla

Answer 18

Question 19

center line in the utricle and saccule where depolarization is in different directions

Answer 19

striola

Question 20

____detect static displacements and linear accelerations of the head induced by tilting or translational movements of the head

Answer 20

Utricle and Saccule

Question 21

the sensory epithelium consisting of hair cells and supporting cells
otolithic membrane

Answer 21

macula

Question 22

what are the crystals that sit on top of the gelatinous cap in the utricle and saccule

Answer 22

otoliths/otoconia

Question 23

the crystals and the gelatinous cap

Answer 23

otolithic membrane inside the utricle and the saccule

Question 24

___ are calcium carbonate crystals

Answer 24

otoconia (otoliths)

Question 25

\_\_\_make otolithic membrane heavier than fluids around it

Answer 25

Otoconia

Question 26

how does utricle or saccule work

Answer 26

when head tilts gravity causes otolithic membrane to shift relative to sensory epithelium. “Shearing” causes displacement of hair cell bundles and a receptor potential in hair cell movement toward the kinocilium → depolarization , movement away → repolarization saccule → movement away from center line (striola) → depolarization utricle → movement toward the center line (striola) → depolarization

Question 27

why is there a “shearing” motion between the sensory epithelium and the otolithic membrane.

Answer 27

During linear accelerations The greater mass of the otolithic membrane causes it to t**emporarily lag** behind the sensory epithelium, leading to transient displacement of hair cell bundle **hair cells move in the opposite direction of the head, temporarily lag**

Question 28

During static tilt hair cell response is \_\_\_

Answer 28

sustained constant because gravity is constant

Question 29

During linear accelerations hair cell response is \_\_\_

Answer 29

transient only occurs with change in velocity

Question 30

head tilt backwards causes \_\_\_, head tilt forward causes \_\_\_

Answer 30

depolarization hyperpolarization

Question 31

\_\_\_ mainly concerned with motion in the horizontal plane

Answer 31

Utricle movement toward the center → depolarization

Question 32

\_\_\_ mainly concerned with motion in the vertical plane

Answer 32

saccule movement away from the striola → depolarization

Question 33

\_\_\_ Detect angular acceleration that result from rotation of the head

Answer 33

semicircular canalas

Question 34

At the base of each semicircular canal is a bulbous expansion called the \_\_\_

Answer 34

ampulla

Question 35

In the semicircular canals, within the ampulla is the sensory epithelium called the ___ that contains the hair cells

Answer 35

crista

Question 36

The hair bundles of the semicircular canal extend into a gelatinous mass called the \_\_\_.

Answer 36

cupula

Question 37

\_\_\_ cannot flow through the cupula

Answer 37

Endolymph cupula is the gelatinous mass on the hair bundle of the crista in the ampulla of the semicircular canal

Question 38

endolymph move ___ to the direction of movement of the head

Answer 38

opposite direction ## Footnote 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 a displacement of the hair bundles

Question 39

When the head turns in the plane of one of the semicircular canals, the \_\_\_of the endolymph produces a force across the \_\_\_, moving it away from the direction of head movement and causing a displacement of the hair bundles

Answer 39

inertia cupula

Question 40

what is the direction of the hair cells in the semicircular tubules?

Answer 40

all in the same direction ( they all either depolarize or hyper polarize based on the direction from the kinocilia)

Question 41

Head rotation moves the \_\_\_in opposite directions for the two partners, resulting in opposite changes in their firing rates

Answer 41

cupula semicircular canal on the right will depolarize and left will repolarize (they are opposite of each other)

Question 42

if I turn my head to the left what direction is the endolymph in the semicircular canals

Answer 42

the left will go right this will cause depolarization the right will go right will cause hyperpolarization

Question 43

\_\_\_ response of vestibular nerve axon from left and right horizontal semicircular canals to left rotation of the head ( angular acceleration)

Answer 43

Transient only respond to change not constant acceleration

Question 44

Hair cells in the left horizontal semicircular canal depolarize when the head turns \_\_\_

Answer 44

left

Question 45

Hair cells in the right horizontal semicircular canal ___ when the head turns left

Answer 45

hyperpolarize

Question 46

pathway from vestibular area to brain

Answer 46

vestibular → CN8 → vestibular nuclei → up to the brain (either the lateral vestibulospinal tract → antigravity muscles or the medial vestibulospinal tract → neck)

Question 47

lateral vestibulospinal tract

Answer 47

Ipsilateral forelimb and hindlimb extensors (antigravity muscles) balance

Question 48

medial vestibulospinal tract

Answer 48

bilateral to motor neurons for neck run through the medial longitudinal fasciculus (MLF)

Question 49

MLF carries information to the neck motor neurons and the ____ nerves

Answer 49

3,4,6 extra ocular motor neurons → stabilize gaze (VOR- vestibulo ocular reflex)

Question 50

VOR

Answer 50

**Vestibulo-ocular reflex (VOR)** Head rotation activates semicircular canals in inner ear and drives compensatory eye movements to stabilize image of visual world on the retina head rotates L → eyes rotate R → gaze remains the same place movement causes depolarization in semicircular canal on one side → this will stimulate the CN3 on the same side to contract the medial recti, it will also cause the CV6 nucleus to cause the lateral rectus of the opposite eye to contract and go through the MLF and also cause the medial recti of the same eye to contract

Question 51

vestibular nystagmus

Answer 51

eyes try to stay on same place can't keep up cause head is moving, will have a slow phase when it is trying, then a fast snap back phase

Question 52

optokinetic nystagmus

Answer 52

moving in car → follow a tree then snap to new tree

Question 53

. A nystagmus induced by looking at moving visual stimuli, such as moving horizontal or vertical lines, and/or stripes.

Answer 53

Optokinetic nystagmus

Question 54

If one spins in a chair continuously and stops suddenly, the fast phase of nystagmus is in the opposite direction of rotation, known as the "\_\_\_\_," while slow phase is in the direction of rotation.

Answer 54

Postrotatory nystagmus

Question 55

damage to one or more components of the vestibular system e.g., Garth: Labyrinthitis or vestibulitis or vestibular disease

Answer 55

pathologic nystagmus

Question 56

Dogs with idiopathic vestibular disease have some combination of the following symptoms:

Answer 56

A head tilt * They are unsteady on their feet and may fall over * Head tilts and animal falls toward the side of the lesion * They circle in one direction or even roll across the floor * Their eyes flick back and forth, up and down, or rotate in a circle (this is called nystagmus) * An unwillingness to eat due to nausea * Vomiting **Moral of the Story: Don't kill old rolling dogs**