Term
| List the components of the vestibular system and the location |
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Definition
Bilaterally located in the temporal bone adjacent to the cochlea.
There are three fluid filled semi-circular canals (anterior, posterior, and horizontal). These deal with angular acceleration.
The macule contains two statolith organs: utricle (more horizontal) and sacule (more vertical). These deal with linear acceleration. |
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Term
| How do the sensors detect acceleration? |
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Definition
| The epithelium is made up of hair cells which have one large hair cell (kinocilia) and smaller hair cells (stereocilia). If the stereocilia bends towards the kinocilia the cell is activated (depolarized). If it bends away from the kinocilia you get inhibition. |
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Term
| In the macule, what makes the hair cells move? |
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Definition
There is an otolith mass with calcium crystals that lies over the hair cells. When a force of intertia is applied to the otolith, it moves and the crystals slide across the hairs causing them to bend.
Remember that F=M•A |
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Term
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Definition
| There are two utricles. The one on the right is bent to the right and the one on the left is bent to the left. This means that if you bend your head to the right, then the right utricle will be activated and the left utricle will be inhibited. If you move your head forward, both utricles will be activated. |
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Term
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Definition
| The sacule is S shaped and functions like a joy-stick. This means that it fires with right, left, forwards, backwards, up, and down movements. So, the saccule plays an important role in and up and down movements, but does not differentiate right from left. |
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Term
| What causes the hair in the semi-circular canals to move? |
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Definition
The hairs are sticking into a structure that has approximately the same density as the fluid in the cannals. A force on one side or the other will cause the hair to bend. When the cannal is rotated, the fluid has inertia and does not move immediately. Since the hair is attached to the canal, it bends. The hair bends in the opposite direction when the canal stops.
For the right cannal, if you rotate to the right, the right cannal will be activated. The left cannal would be inhibited. |
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Term
| How does linear acceleration effect the semi-circular canals? |
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Definition
| Linear acceleration does not effect the semi-circular canals because everything moves together rather than the canal rotating first. |
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Term
| Information from the vestibular system goes to the _______ which also gets information from the _______. This information is then communicated with what primary neurons? |
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Definition
| Information from the vestibular system goes to the vestibular nuclei which also gets information from the muscle and joint receptors in the neck. Some of this information goes to the motor neurons to adjust posture and some of the information goes to the ocular neurons to allow coordination with the motor neurons. |
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Term
| Define the lifting response |
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Definition
| extensor tonus is decreased during lifting and increased during falling |
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Term
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Definition
Slow component: eyes slowly move in the opposite direction that a person is being turned
Fast component: once a critical point is reached (the focal point can no longer be seen), the eyes rapidly move in the direction of the rotation
Clinically the direction of nystagmus is defined by the rapid component. |
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Term
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Definition
The canal is stimulated with either warm or cold fluid, which causes the fluid to rotate. Cold water will stimulate the opposite side and result in nystagmus towards the opposite side. Warm water will stimulate the same side and result in nystagmus towards the same side.
Remember COWS- Cold Opposite Warm Same-side |
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Term
| Discuss the Barany Chair Test |
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Definition
| If someone is spun in a chair, when the chair is stopped they will have nystagmus in the opposite direction of the rotation. This is postrotary nystagmus because the body thinks it is spinning in the opposite direction. If the person tries to walk they will fall in the same direction they were spun because the extensor muscles on the opposite are active. |
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