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Nervous System: Unit III > Vestibular System > Flashcards

Flashcards in Vestibular System Deck (15)
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1
Q

Vestibular system fxn

A
  • detects stimuli that reflect rotation of the head (dynamic processes) AND
  • head’s orientation w/respect to gravity (dynamic and static processes
  • w/visual, proprioceptive and tactile info ==> sense of balance
2
Q

Components of the vestibular system

A
  • sensory end organs @ inner ear
    • utricle and saccule
    • semicircular canals
  • sensor types:
    • two pairs of otolith organs = utricle and saccule
      • detect linear acceleration and direction of gravity vector
    • three pairs of semicircular canals
      • detect head rotation (angular acceleration)
3
Q

Longest stereocilia =

“Axis of polarity” =

A
  • “kinocilium”
  • axis of polarity = the direction of the arrow that bisects the bundle toward the kinocilium
4
Q

Physiology of hair cell fxn

A
  • Bending of hair cell bundle in direction of axis of polarity ==> depolariztion ==> NT release ==> ANF firing increases
  • depolarization = via mechanical spring (“tip link”) stretching from tips of stereocilia ==> stretching and opening of K+ channels
5
Q

Structure/fxn of the utricle

A
  • horizontal orientation like seat of chair → linear acceleration
  • does a side to side tilt or a front to back rocking
  • Senses forward acceleration like in a car
  • Hairs lined up towards striola
  • **roles reversed when lying down
6
Q

Structure/fxn of the saccule

A
  • vertical orientation like back of chair → gravitational sensations
  • elevator sensations
  • bouncing
  • falling sensations
  • Hairs lined up away from striola
  • **role reversed when lying down
7
Q

Characteristics of the macula

A
  • =sensory epithelium @ succule and utricle
  • = hair cells + associated supporting cells
  • overlaying hair cells/bundles ==> gelantinous layer
  • ==> fibrous structure = otolithic membrane
    • embedded otoconia = crystals of calcium carbonate
8
Q

Characteristics/properties of otoconia

A
  • ==> otolithic membrane heavier than structures/fluids surrounding it
  • increased weight ==> increased relative displacement when head is tilted (or undergoes linear acceleration)
  • ==> shearing motion between otolithic membrane and macula ==> displacement of hair bundles
9
Q

Characteristics of semicircular canals

A
  • 3 canals = anterior, horizontal and posterior
  • @ base of each canal, there is a bulbous expansion = ampulla
    • houses sensory epithelium (“crista”) that contains hair cells
    • hair bundles extend ==> cupula (gelatinous mass)
    • cupula = bridges width of ampulla & prevents endolymph from passing
10
Q

Mechanism of rotational acceleration sensation

A
  • occurs @ semicircular canals
  • cupula is distorted by movements of the endolymphatic fluid.
  • head turns in the plane of one of the semicircular canals ==>
  • inertia of the endolymph produces a force across the cupula ==> distending it away from the direction of head movement
  • ==> displacement of the hair bundles
11
Q

Vestibular motor reflexes

A
  • vestibulo-ocular reflexes (VOR)
  • vestibulocollic reflexes (VCR)
  • vestibulospinal reflexes (VSR)
12
Q

Characteristics of vestibulo-ocular reflexes (VOR)

A
  • vestibulo-ocular reflexes (VOR) allow the eyes to maintain focus on a point of interest during head movement
  • If you’re missing VOR ==> “video-camera vision”
    • i.e. like having a bad video in front of you every minute
13
Q

Characteristics of vestibulocollic reflexes

A
  • vestibulocollic reflexes (VCR) help maintain head stability and upright stance of the head
14
Q

Characteristics of vestibulospinal reflexes (VSR)

A
  • vestibulospinal reflexes (VSR) assist balance and provide a framework for coordinated motion of the limbs during ambulation
  • No conscious though is used on placement of arms and legs to help you balance, and if you do fall, they move to break the fall
15
Q

What is the three neuron arc?

A
  • VOR
  • Shortest reflex in body
  • Allows eyes to stay focused when turn head