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57 Cards in this Set

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