Term
| What two types of measurements does the vestibular system use to provide head orientation? |
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Definition
1. Linear acceleration
2. Angular acceleration |
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Term
| What part of the vestibular system senses linear acceleration and which part senses angular accelerations? |
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Definition
Linear - otolith organs
Angular - semicircular canals |
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Term
| What are the 3 canals that make up the labyrinth? |
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Definition
1. Anterior
2. Posterior
3. Horizontal |
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Term
| What are the 3 layers of the bony canal? |
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Definition
1. outline
2. Perilymph (CSF)
3. Endolymph (membraneous) |
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Term
| In what parts of the vestibular system are the hair sensor cells located? |
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Definition
| Maculae and Cristae ampullaris |
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Term
| The 3 canals come together at what part of the vestibular system? |
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Definition
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Term
| Where are the detectors of vertical and horizontal position located in the vestibular system? |
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Definition
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Term
| The cristae ampullaris and maculae are located in what parts of the vestibular system? |
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Definition
Cristae ampullaris - semicircular canals
Maculae - otolith |
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Term
| What 2 classes do the microvilli of hair cells fall into? |
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Definition
1. Stereocilium
2. Kinocilium (tallest one) |
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Term
| How does the ionic content of the endolymph differ from that of the perilymph and how is this maintained? |
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Definition
[K]. Perilymph is typical extracellular fluid ([K] ~ 4mM) whereas in the endolymph [K] ~ 150mM
Tight junctions in the hair cells maintain this separation. |
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Term
| The gelatinous mass is in what part of the vestibular system? |
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Definition
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Term
| How do the microvilla on hair cells move as a fundamental unit? |
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Definition
| Tip links cross linking adjacent microvilli |
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Term
| Explain how head movement is transduced in hair cells |
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Definition
| The inertia of the gelatinous mass makes it resist changes in motion, so relative motion of the hair cells relative to the gelatinous mass cause bending in the hair cells. This bending causes stress in the tip links, which cause a variation in the permeability of ion channels (Potassium is the most important). This depolarization of the cell causes the release of neurotransmitters (glutamate) to the vestibulocochlear nerve. |
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Term
| Explain how the hair cells can sense which direction the movement is in |
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Definition
| Movement toward the kinocilium causes an increase in open channels and ion flow whereas movement away from the kinocilium causes a decrease in ion flow and NT release. |
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Term
| Describe the orientation of the hair cells in the maculae and cristae ampullaris |
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Definition
Maculae - vertical, two orientations
Cristae ampullaris - horizontal |
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Term
| How does the gelatinous mass of the otolith organs differ from that found in the semicircular canals? |
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Definition
| A much higher concentration of calcium carbonate crystals in the otolith organs makes it heavier |
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Term
| What is the dividing line in the orientation of the otolith hair cells called? |
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Definition
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Term
| How does the firing of otolith organ hair cells differ from that of the semicircular canals? |
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Definition
| The increased mass of the gelatinous mass makes the hair cells stay pushed in a certain direction. This leads to them continuously firing, leading to the generation of a POSITION signal as opposed to an ACCELERATION signal |
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Term
| What does the medial longitudinal fasciculus integrate the vestibular system with and where does it go to? |
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Definition
1. Control of eye movement relative to head location
2. Optic cranial nerves (3, 4, 6) |
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Term
| What does the medial vestibulospinal tract carry information for and where does it go? |
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Definition
1. Neck and trunk movement relative to head position
2. Cervical spinal cord |
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Term
| What does the lateral vestibulospinal tract carry information for and where does it go? |
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Definition
1. limb and trunk movement relative to head position
2. medial parts of the ventral horn |
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Term
| Does the vestibuloocular reflex depend on vestibular or ocular inputs or both? |
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Definition
| Vestibular. No light input is involved in this reflex. |
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