chapter 12-spatial orientation and the vestibular system Flashcards Preview

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Flashcards in chapter 12-spatial orientation and the vestibular system Deck (88):
1

problems with the vestibular system can lead to peculiar sensations

spatial disorientation, dizziness, vertigo, imbalance, blurred vision, illusory self-motion

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spatial disorientation

any impairment of spatial orientation (sense of linear motion, angular motion, or tilt)

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dizziness

nonspecific spatial disorientation; no specific direction

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vertigo

sensation of rotation or spinning

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vestibular organs/vestibular system

the set of five organs (3 semicircular canals and two otolith organs) located in each inner ear that sense head motion and head orientation with respect to gravity

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vestibular organs help us in many ways, for instance; provide a sense of spatial orientation consisting of

linear motion, angular motion, tilt

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spatial orientation

a sense comprised of three interacting sensory modalities; our sense of linear motion, angular motion and tilt

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angular motion

rotation; can be sense when rotating head from side to side as if to say "no"; fluid motion

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linear motion

sensed when accelerating or decelerating in a car; motion of hard substance/intertia

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tilt

can be sensed when nodding head up and down as if to say "yes"; gravity

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fluid and inertia processes what

acceleration, changes in velocity; starting and stopping motions

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gravity processes what

acceleration force, constant acceleration

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spatial orientation coordinates system for classifying direction on how many axes that are relative to what

3 axes; defined relative to the head of the person, independent of gravity

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x axis

points forward, in the direction the person is facing; forward and backward

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y axis

point laterally, out of the persons left ear; left and right

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z axis

point vertically, out of the top of the persons head; up and down

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linear motion-translation of movements

represented in terms of changes in the x y and z axes; any arbitrary linear motion can be represented as a change along these three axes

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linear motion; vector

amplitude (degree of acceleration and velocity, size of head movement), direction (line one moves along)

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three directions for sense of rotation

roll, pitch, yaw

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roll

rotation around the x axis (maybe)

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pitch

rotation around y axis (yes)

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yaw

rotation around z axis (no)

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tilt

more of a constant position vs a motion

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tilt is in regard to 2 axes

x and y

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semicircular canals

the three toroidal tubes that sense angular acceleration, a change in angular velocity;

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otolith organs

mechanical structures that sense both linear acceleration and gravity

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otolith organs offer sense of

linear velocity and tilt; hard structure inside that gets shifted within

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semicircular canals source of

our sense of rotation; slosh fluid back and forth

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semicircular canals have how many directions

3; anterior, posterior, horizontal

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otolith organs are more localized; __ of them

2; utricle and saccule

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hair cells are in semicircular canals and otolith organs

support the stereocilia that transduce mechanical movement in the vestibular labyrinth into neural activity sent to the brain stem

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mechanoreceptors are in semicircular canals and otolith organs

sensory receptors that are responsive to mechanical stimulation (pressure, vibration, movement)

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hair cells act as ____ in each of the five vestibular organs

mechanoreceptors

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head motion causes hair stereocilia to ___, causing a change in hair cell ___ and altering ___ release (___ response)

deflect, voltage, neurotransmitter, gradient

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degree to which stereocilia are bent determine how much ____ is released

neurotransmitter

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hair cell responses; in the absence of stimulation

hair cells release neurotransmitter at a constant rate

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hair cell responses; increase firing to rotation

in one direction and decrease firing to rotation in the opposite direction

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hair cells have a ___ constant rate

high; ~100 spikes/sec vestibular nerve fibers

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convey info by

increase or decreasing firing rate

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depolarization

increase action potential rate

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hyperpolarization

decrease action potential rate

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amplitude

coded here in response rate; larger amplitude is depolarization

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stereocilia not all the same height; bend to tallest

depolarization

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stereocilia not all the same height; bend away from tallest

hyperpolarization

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semicircular canals are filled with fluid and are what shaped

three-fourths of a toroid (donut shape)

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ampulla

cross section of each canal swells substantially near where the canals join the vestibule

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base area of semicircular canals is the

ampulla; hair cells that get activated by movement

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edolymph

fluid thats moving around

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semicircular canals are more sensitive to

certain areas; ex. horizontal semicircular canal responds to yaw rotation

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push pull symmetry

hair cells in opposite ears respond in a complementary fashion to each other; when hair cells in the left ear depolarize, those in the analogous structure in the right ear hyperpolarize; overall activation is different between the 2 ears

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tallest stereocilia located in the back; fluid in both ears moves

in the opposite direction of head motion, increase in one ear and decrease in the other ear

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horizontal canal responds to what rotations

yaw

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left posterior canal and ___ paired together

right anterior canal

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right posterior canal and ___ paired together

left anterior canal

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semicircular canal dynamics (fluid movement); neural activity is sensitive to

changes in rotation velocity

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constant rotation of semicircular canal lead to decreased

responding from the canal neurons after a few seconds

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semicircular canal dynamics have a burst of activity at ____; fluid stops moving with ____ ____; when you stop moving the fluid moves ____

acceleration; constant movement; backward

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otolith organs sense what

acceleration and tilt

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two otolith organs in each ear

utricle and saccule

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utricle has how many hair cells

30,000

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saccule has how many hair cells

16,000

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hair cells in otolith organs are encased in what

otoconia

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otoconia

gelatinous structure that contains calcium carbonate crystals

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hair cells in otoconia have similar push pull symmetry because the stereocilia

converge

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coding of amplitude in the otolith organs; larger accelerations move

the otolith organs otoconia more, and leads to greater deflectin of the hair cell bundles

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response from tilt

substained

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response from rotational and linear

transient

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directional coding in the otolith organs arises from

anatomical orientation of the organs

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directional coding in the utricular macula

horizontal plane; tilt side to side

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utricular macula movement is sensitive to

horizontal linear acceleration and gravity

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directional coding in the saccular macula

vertical plane; tilt vertical

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saccular macula movement is sensitive to

vertical linear acceleration and gravity

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rotation perception

at first, constant rotation in the dark is perceive accurately. soon subjects feel as though they are slowing down. after 30 seconds, they no longer feel as if they are rotating.

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velocity storage

time course habituation for perceived velocity is slower than time course of habituation for velocity neurons

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tilt perception

accurate for perceiving tilt for angles between 0 degrees (upright) and 90 degrees (lying down)

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tilt perception illusion

if you roll tilt your head to the left or right while looking at a vertical streak of light, the light appears to tilt in the opposite direction

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sensory integration

the process of combining different sensory signals; leads to more accurate information than obtained from individual senses alone

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visual vestibular integration

vection

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vection

illusory sense of self motion produces when you aren't actually moving

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sensory integration; observers looking at a rotational display report

rotational vection; subjects have the illusion of tilt but still feel vertical

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why don't people feel as if they are turning upside down

the vestibular systems sense of gravity stops the illusion

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vestibulo-ocular reflexes (VORs)

counter rotating the eyes to counteract head movements and maintain fixation on a target; keep eyes fixated on stimuli by moving them in the opposite direction of the head

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vestibulo-autonomic responses include

motion sickness, vertigo

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motion sickness

results when there is a disagreement between the motion and orientation signals provided by the semicircular canals, otolith organs, and vision; could be an evolutionary response to being poisoned

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vertigo

distorted perception of orientation relative to vertical, or motion relative to the environment, accompanied by dizziness, nausea, vomiting, and postural instability; height vertigo and postural alcohol mystagmus

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blood pressure is regulated by

vestibulo autonomic responses

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height vertigo

body movement size no longer matches the visual angle changes

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postural alcohol mystagmus

alcohol changes the density of semicircular canals