lec 7 - vestibular system - unfinished

vestibular system processs _______ information underlying _____ and ______

• _____

• _____

• _____

sensory information; motor responses to; perceptions of

• self-motion

• head posiition

• spatial orientation relative to gravity

helps to stabilize

gaze, head, posture

key component in

postural reflexes

eye moement

______ critical to ______

“sixth sense”

autonomic behaviors and perception

damage to the vestibular system can cause issues with

balance

stabilizing our gaze while moving head

spatial orientation

what types of acceleration does the vestibular system sense

linear

rotational

vestibular system converts the effects of ____ into neural impulses

gravity

(linear/rotational accelerations)

The three semicircular canals are oriented to detect ______ around the 3 cardinal axes

rotational motion

What are the three cardinal axes? give the names for rotation around these axes.

x, y, z

roll, pitch, yaw

which type of acceleration

• otolith organs

• semicircular canals

• linear

• rotational

Approximately _____ of US population will experience some form of dizziness or balance difficulty in their lifetim

40%

Symptom reports of dizziness and imbalance in adults increase with

age

____% of adults—_____Americans—report a chronic problem with balance

4

8 mil

____ of adults (____) report a chronic problem with dizziness

1.1%

2.4 mil

the main peripheral component of the vestibular system

labyrinth

labyritnth and cochlea

works similar to cochlea

continuous with it

the labyrinth converts ______ into ______

physical motion from gravity/linear and rotational acceleartions of the head

neural impulses

parts of the labyrinth

• 2 otolith organs (linear acceleartions, static head position relative to gravitational axis (head tilts))

• 3 semicircular canals (rotational)

• vestibular hair cells

vestibular hair cells are located

utricle, saccule, ampullae

vestibular hair cells work like

auditory hair cells

some transduction channels are open in the ______

absence of stimulation

vestibular system baseline - high or low

high, lots of spontaneous activity

hair cells in 3 organs are _____ for certain directions

selective

striola

divids hair cells into two population

which way do hair cells point in the

• ampulla

• sacculus

• utricle

• same direction

• away from the striola

• towards the striola

if hair cells are diplaced towards the tallest stereocilia:

smallest steroocilia:

tallest = depol

smallest = hyperpol

K cascade leads to which neurotransmitter release

glutamate

Firing rates of vestibular fibers can increase or decrease in a manner that

Faithfully mimics the receptor potentials produced by the hair cell

otolithic membrane is a _____ layer with small crystals called ____ which _____ hair bundles during tilting motion

gelatinous

otoconia

deflect

utricle: _____ movements

saccule: _____ movements

horizontal

vertical

depolarizing one otolith organ →

hyperpolarizing the other

utricle

• head tilt backwards

• head tilt forwards

• no head tilt + forward accel

• no head tilt + forward decel

• depol

• hyperpol

• depol

• hyperpol

Hair bundle movement occurs

• _____ in response to tilting of the head

• _____ in response to acceleration

• tonically

• transiently

constant head tilt = ______ firing

constant

B

bulbous expansion at the base of each canal

ampulla

ampulla of each canal houses ______ that contains the _____

sensory epithelium/crista

hair cells

hair cells extend out of the crista into a gelatinous mass, the ____

cupula

viscous barrier in the semicircular canals through which endolymph cannot circulate

cupula

hair cells/cupulae have ______ orientation on either side of the head

opposite

when the head rotates, fluid in the canal

distorts the cupula

endolymph fluid flow vs head movement

flow goes opposite to head movement

Each semicircular canal works in concert with

The partner located on the other side of the head that has its hair cells are lined oppositely

3 pairs of semicircular canals

• right/left horizontal

• left ant + right post

• right ant + left post

push-pull arrangement - head rotations deform the cupula in _____ dirrections for the two partners, resulting in ____ changes in firing rate

opposite

opposite

(provides info about rotation of head in any direction)

turn head to left - ____ depol and ____ hyperpol

left

right

semicircular canals

• acceleration = ____ firing rate

• deceleration = ____ firing rate

• constant v = ____ firing rate

• max

• min

• baseline

C

Central vestibular processing is inherently _____

multisensory

Many neurons in the vestibular nuclei function as _____ neurons in addition to giving rise to _____

premotor

ascending sensory projections

Central projections from vestibular nuclei are involved in 2 major classes of reflexes:

• Helping to maintain equilibrium and gaze during movement

• Maintaining posture

vestibulo-ocular reflext

eye movements counter head movements

maintains gaze fixation

VOR pathway

C

Rotating the head elicits _____ which consists of a ____ eye movement _____ the direction of head turning

• due to ____

physiological nystagmus; slow; counter to

• relative differences in firing

When one canal is damaged, _____ occurs, due to _____

spontaneous nystagmus

the tonic firing of fibers from the opposite canal