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57 Cards in this Set
- Front
- Back
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What are the major components of the vestibular system?
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semicircular canals
utricle sacculus |
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How are the semicirc. canals oriented? How many are there?
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orthogonally (at right angles); 3
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What do the SC canals do?
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sense head rotations and respond to angular accelerations
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What structure is specialized for sensing linear (mainly horizontal) accelerations?
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utricle
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What structure is involved with vertical linear accelerations? An example of a vertical linear accleration?
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sacculus; gravity
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What is yaw?
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turning head around the vertical axis (like shaking head "no")
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What is pitch?
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axis describing nodding head in "yes" motion
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What is roll?
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moving aroudn axis used to laterally bend head (ear towards shoulder)
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What does the vestibular system do?
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1. generates compensatory eye movements in response to head movements (vestibulo-ocular)
2. helps maintain our head position despite our body movements (vestibulo-colic) 3. helps us maintain our posture if we start to fall over (vestibulospinal) |
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The vestibular system provides a compensatory signal during head movements with a very (short/long) latency. How does this compare to the latency of the visual system.
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short (~6-10ms);
much shorter, the visual system latency is ~200ms |
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What is the most important system for balance?
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vestibulospinal
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The vestibular system sends signals to make postural changes mainly to ______ muscles.
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extensor
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The major players in the vestibular system are the _______.
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hair cells
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When the sterocilia move in the direction of the kinocilia it will cause....
If the stereocilia move in the opposite direction... |
stretch and K+ will flow into the HC;
K+ stops flowing |
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Is signaling in the vestibular system similar to or different from signaling in the auditory system?
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similar, displacement of cilia is different
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In the ampulla, all the stereocilia are oriented in (one/different) directions.
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one
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What is the swelling at the base of the semicircular canal called?
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ampulla
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The stereocilia are connected to a _______ to catch the endolymph as it moves.
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cupula
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What is the dividing component that is in both the sacculus and the utricle?
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the striola
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What does the striola do?
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it divides hair cell populations into bundles with opposing hair bundle polarities
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The orientation of the sterocilia and kinocilia are reflected along the ______.
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striola
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How are the cilia oriented in the sacculus? the utricle?
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S: up on one side of the striola and down on the other
U: one way on one side and the opposite way on the other |
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How does the orientation of the cilia affect signaling? What is this signaling called?
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causes signals that stimulate one group to oppose the other; push-pull signaling
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What are otoconia?
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calcium carbonate crystals sitting in the macula
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Where do the otoconia sit?
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on top of a gelatinous membrane which the hair cells project into
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What happens when gravity acts on the otoconia?
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they will displace the gelatinous membrane along with the stereocilia in a specific direction
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What two things can activate the otoconia system in the macula?
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1.static tilt (gravity is causing otoconia to move toward the ground which causes the hairs to bend
2.rapid acceleration (also causes hair to bend) |
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T/F: The vestibular system can actually get confused between tilting and linear acceleration
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True
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How does your body tell the difference between tilting and linear acceleration?
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based on how long the stimulus lasts (a short transient stimulus is acceleration, a sustained effect is interpreted as tilt)
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There is a ______ firing rate from the hair cells in both the otolith systems and semicircular canals.
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tonic
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How does accelerating in one direction versus another affect the firing rate?
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one direction will increase firing rate and the other direction will decrease firing rate
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What is the sail-like membrane in which hair cells send their stereocilia up into?
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cupula
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What happens to fluids in the SC as you move your head?
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they move and exert a force on the cupula which causes the stereocilia of the HCs to be deflected
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What happens if the stereocilia of the HCs are deflected towards the kinocilia? away from the kinocilia?
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towards: depolarization and increased firing of the vestibular nerve
away: firing rate will decrease |
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T/F: Each semicircular canal can sense signal acceleration only one direction.
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False, in 2 directions
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How are the L and R horizontal canals oriented?
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at about 30 degrees upward of horizontal
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If you tilt your head 30 deg down?
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1.You isolate the horizontal canal
2.Bring the utricles into the horizontal plane 3.bring the sacculus into the vertical plane |
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How do you test for horizontal canal function?
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tilt the head down 30 deg and rotate the head (isolates the horizontal canal)
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Which SC canals are in the same parallel plane?
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RALP: Right Anterior with Left Posterior
LARP: Left Anterior with Right Posterior |
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What happens in the SC canals with movement of the head to the left?
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-Endolymph moves to the right because of inertia
-this moves the stereocilia in in the left duct in the direction of their axis of polarity -therefore exciting the afferent fibers to increase their firing rate (the opposite happens to the stereocilia of the duct on the right) |
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The SCs respond to _______ _______ but the signals recorded from the vestibular nerve are related to ______ ________.
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angular accleration
head velocity |
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What does the fluid in the SC canals do?
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acts as a dampening factor
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As you turn your head the system that is really moving the ________ causes the ________ nerve to send a signal to the brain that is related to head velocity.
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cupula; vestibular
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How do your eyes move when your head moves?
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they move in the opposite direction but at the same velocity
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What is the vestibulo-ocular reflex (VOR)?
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a very rapid response so that despite head moving left/right or up/down your eyes can stay fixed on an object of interest
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What might happen if all the inner hair cells are destroyed?
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might have trouble seeing while walking because the vibrations of walking cause eyes to shake
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Where does the signal come from in VOR? where might it go?
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vestibular nerve; medial vestibular nucleus
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Explain what happens in the VOR when the head rotates left.
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-signals from the L medial vestibular nucleus make excitatory connections on the R abducens nucleus
-via the MLF make excitatory connections on the L oculomotor nucleus (for medial rectus) -at the same time, the L MVN makes inhibitory connections on the ipsilateral (L) abducens nucleus and on the contralateral (R) oculomotor nucleus |
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How does spinning cause ocular nystagmus?
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when you spin slowly at a constant spped the fluid in the SCs wont' be accelerating and the cupula will return to its initial position,
-when you stop spinning the fluid decelerates moving the cupula in the opposite direction |
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What are the lateral vestibulospinal tracts involved in?
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body tilting and preventing you from falling over
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In response to body tilting there will be activation of _________ motor neurons, primarily to __________ muscles.
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ipsilateral; extensor
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What happens if you transect above the level of the vestibular nuclei?
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you observe decerebrate rigidty in which all extensors of the limbs are activated to prevent you from falling, you lose the voluntary component
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What is the medial vestibulospinal tract's purpose?
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primarily modulating head position
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What is the vestibulo-colic reflex?
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part of the medial vestibulospinal tract; activated when you fall asleep in class --> signal to neck muscles to pull head back up
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T/F: The vestibular system degenerates over time
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true, so the elderly become more reliant on visual cues for balance and have more problems with falls
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Cells in the lateral and superior vestibular nuclei relay in the _______ and then project to the ______.
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Thalamus (VPL); vestibular cortex
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What are some regions of the vestibular cortex?
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Area 3a (primary sensory cortex)
Parietal cortex |
