Glossary of SFS - Vestibular System
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- How are the semicircular canals oriented? What are the 3 canals? What do they sense?
- orthogonally (right angles). Horizontal, superior/anterior, posterior.
Head rotations and respond to angular accelerations.
- Specialized for horizontal linear accelerations
- Specialized for vertical linear accelerations
- 1. Head around vertical axis.
2. Axis of head nodding yes.
3. Around axis used to laterally bend head.
- 1. Yaw.
- Generates compensatory eye movements in resonse to head movements
- Vestibulo-ocular reflex. Have to go over 2 Hz to lose ability to stay focused.
- Provides a compensatory mechanism with a very short latency.
- Vestibular system. Visual system has a much slower latency.
- Maintain head position despite body movements
- Vestibulo-colic reflexes
- Helps maintain our posture if we start to fall over. Most important system for balance. Sends signals mainly to extensor muscles.
- Major players in vestibular system (just like auditory)
- Hair cells
- When stereocilia move in direction of the kinocilium, what will happen? What about the opposite direction?
- It will cause stretch and potassium will flow into the hair cell.
Opposite direction - potassium stops flowing.
- Swelling at base of each semicircular canal?
- In the ampulla, how are the stereocilia oriented?
- In a single direction to sense canal rotation. Cilia are connected to a cupula to catch the endolymph as it moves.
- Dividing component of sacculus and utricle.
- Signaling in sacculus and utricle.
- Push-pull. Orientation casuses signals to stimulate one group and oppose the other.
- 1. Maximal sensitivity in the sacculus.
2. Maximal sensitivity in the utricle.
- 1. Vertical linear acceleration.
2. Linear accelerations in the horizontal plane.
- Calcium carbonate crystals and where they reside.
- Otoconia. Reside in the macula.
- Two things that can activate the hair cells via otoconia in the sacculus and utricle.
- Static tilt and rapid acceleration.
Both cause hairs to bend. Vestibular system can actually get confused between the two and give the same signal.
- How does the body tell the difference between tilt and acceleration?
- Short, transient effect interpreted more as acceleration while a sustained effect is interpreted as tilt.
- The hair cells in the sacculus, utricle, and semicircular canals respond to acceleration or deceleration via a __________ relationship.
Stimulating in one direction will increase the firing from the tonic firing already occuring, while stimulation in the opposite direction will cause a decrease in firing rate.
- In the SC, hair cells send their stereocilia up into what?
- cupula (spreads across ampulla)
- Rotation of the head causes fluids within the SC to move and exert force on the cupula. This causes what to be deflected?
- The stereocilia. Causing an increase/decrease in firing of the vestibular nerve.
- Tilt head to what to isolate the horizontal canal?
- 30 degrees downward. Also brings utricles into horizontal plane and sacculus into the vertical plane.
- Right anterior canal is paired in parallel plane with which canal?
- Left posterior
- Left anterior canal is paired in parallel plane with which canal?
- Right posterior
- Canal pairs point ____ degrees in their respective direction.
- Within the pairs, moving in a direction will _________ firing in one, and ________ firing from the other.
- Increase, decrease. Stupid question, I know.
- SCs respond to _______, while the signals from the vestibular nerve are related to __________.
- angular acceleration, head velocity
- Net effect of turning your head on the semicircular canal system.
- The cupula is moved, causing the vestibular nerve to send a signal to brain related to head velocity.
- Why is it important that vestibular nerve records signals related to head velocity?
- To use head velocity to control eye velocity.
- Very rapid response, so that despite head moving left/right or up/down, your eyes can stay fixed on an object of interest.
- Vestibulo-ocular reflex.
- Caused when vestibular system is in conflict with the visual system.
- In the VOR, signals come in from vestibular nerve and go where?
- To medial vestibular nucleus
- If head rotates left, signals from the left MVN make _________ connections on the contralateral abducens nucleus and via the MLF make _________ connections on the left oculomotor nucleus.
- excitatory, excitatory
- When head rotates left, the left MVN makes _________ connections on the ipsilateral abducens nucleus and via MLF contralateral oculomotor (right) nucleus
- Goal of VOR.
- Eyes move in opposite direction of the head at an appropriate velocity.
- Causes ocular nystagmus and dizziness due to the VOR.
- IF you continue to spin slowly at a constant speed, the fluid in the SCs won't be accelerating and the cupula will return to its natural position. When you stop spinning, the fluid decelerates moving the cupula.
- VOR handles high frequency stimulation well, but has problems with what?
- slow, continuous stimluations
- Primarily influenced by the otolith, utricle, and sacculus. Involved with body tilting and preventing falling over.
- Lateral vestibulospinal tracts
- In response to body tiliting there will be activation of what motor neurons?
- If you transect above the level of the vestibular nuclei, you will observe what type of rigidity?
- Decerebrate rigidity in which all extensors of the limmbs are activated to prevent you from falling.
- Primarily modulate head position. Vestibulo-colic reflex.
- Medial vestibulospinal tracts. Example is dozing off and waking in class (signal to neck muscles).
- Does the vestibular system degenerate over time?
- YES. Elderly are more reliant on visual cues for balance, and have more problems with falls.
- Cells in the lateral and superior vestibular nuclei relay where? Where do they project after that?
- Thalamus (VPL). Vestibular cortex (ex. Area 3a - primary sensory cortex, parietal cortex)
- What area of the cortex involved in the vestibular system helps you remember where other objects are located in relation to your body in space.
- Parietal cortex
- Eye movements allowing you to:
1. Look back and forth between tow stationary points.
2. Track a moving object
3. Look at objects at different distances.
- 1. rapid seccadic eye movements
2. smooth pursuit
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