Term
| What sensory system provides the most information about spatial orientation and balance? |
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Definition
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Term
| What are the receptor cells of the vestibular system? |
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Definition
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Term
| What is the function of vestibular hair cells? |
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Definition
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Term
| What are the two membrane areas of receptor cells? |
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Definition
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Term
| What is contained in the apical membrane of hair cells? |
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Definition
| One kinocilium and several other cilia |
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Term
| What is the kinocilium? Where is it? |
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Definition
| A long cilium on the apical membrane of a hair cell |
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Term
| How are the cilia on the apical membrane of a hair cell arranged? |
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Definition
| From shortest to longest. All of the cilia except the kinocilium are bundled together. |
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Term
| What is the function of the basolateral membrane of hair cells? |
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Definition
| It makes synaptic contact with an afferent nerve fiber. |
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Term
| Through which cranial nerve do the afferent fibers complexed with the basolateral membrane of hair cells project to the central nervous system? |
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Definition
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Term
| True or false: the cilia of hair cells are directionally sensitive? |
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Definition
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Term
In one hair cell, the bundle of shorter cilia bend TOWARD the kinocilium.
A. Is the cell hyperpolarized or depolarized?
B. Stimulated or inhibited?
C. What has caused this mechanically?
D. What is happening to the cations? |
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Definition
A. Depolarized
B. Stimulated
C. Mechanically gated cation channels are opened by this movement, allowing cations to flow through channel pores.
D. K+ and Ca2+ move down electrochemical gradient INTO the hair cell. |
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Term
| In one hair cell, the bundle of shorter cilia bend AWAY from the kinocilium. Is the cell hyperpolarized or depolarized? Stimulated or inhibited? What has caused this mechanically? What is happening to the cations? |
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Definition
A. Hyperpolarized
B. Inhibited
C. Mechanically gated cation channels are closed by this movement
D. Cations cannot move into the hair cell |
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Term
| Why does bending in one stereocilium cause bending in its neighbor? |
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Definition
| Physical linkages connect adjacent stereocilia, which also connect mechanically gated cation channels. |
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Term
A. What type of extracellular fluid surrounds the APICAL surface of hair cells?
B. Does it more closely resemble cerebrospinal fluid or cytoplasm?
C. What is the relative balance of K+ and Na+ in the fluid? |
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Definition
A. Endolymph
B. Cytoplasm
C. High in K+, low in Na+ |
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Term
A. What type of extracellular fluid surrounds the basolateral membrane of the hair cell?
B. Does it more closely resemble cerebrospinal fluid or cytoplasm?
C. What is the relative balance of K+ and Na+ in the fluid? |
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Definition
A. Perilymph
B. Cerebrospinal fluid
C. Low in K+, high in Na” |
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Term
| Which neurotransmitter is involved in hair cells? |
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Definition
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Term
| Is the resting potential inside a hair cell positive or negative? |
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Definition
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Term
A. What next steps occur after the bending of stereocilia in hair cells TOWARDS the kinocilium causes K+ and Ca2+ to enter its channel pores?
B. Is neurotransmitter release upregulated or downregulated?
C. Is rate of firing the the afferent nerve fibers increased or decreased? |
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Definition
A. The depolarizing receptor potential generated in the cilia on the apical membrane causes the basolateral membrane to depolarize. This opens voltage-gated Ca2+ channels on the basolateral membrane.
B. Calcium influx causes exocytosis of transmitter vesicles, upregulating neurotransmitter release.
C. Increased. |
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Term
A. Do unstimulated hair cells in their resting state release glutamate?
B. Is there a firing in the afferent fibers at this state? |
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Definition
A. Yes, at a low, steady rate.
B. Yes, there is a tonic level of firing that movement of hair cells increases or lessens, depending on direction. |
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Term
| Do hair cells generate an action potential? |
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Definition
| No. Their depolarization causes neurotransmitter to be released, which is graded dependent upon the magnitude of the depolarization. |
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Term
| In which direction do the stereocilia of a hair cell have to move to decrease the release of glutamate and the firing of afferent fibers? |
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Definition
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Term
| How does the movement of isolated hair cells relate to the function of vestibular organs? |
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Definition
| One hair cell responds to the bending of its cilia, but the vestibular organs respond to the rate of change of movement of the entire head |
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Term
| What are the two types of components of the vestibular system, which correspond to the two types of movements we make through space (translational and rotational)? |
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Definition
A. otoliths
B. semicircular canal system |
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Term
| To what other parts of the body does the vestibular system primarily send signals? |
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Definition
* the neural structures controlling eye movements
* the muscles that keep us upright |
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Term
| You nod your head and then do a cartwheel (cleverly making use of your frontal and sagittal planes of movement). Which semicircular canals have you just activated? |
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Definition
| the anterior and posterior semicircular canals |
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Term
| You decide to do a pirouette (transverse plane). In which semicircular canal is fluid now moving? |
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Definition
| The horizontal semicircular canal |
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Term
| As you pirouette to the right, your VOR makes sure that the wall in front of you remains at the center of your visual field. In which direction does the VOR make your eyes move? |
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Definition
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Term
| As you pirouette to the right, you have moved your head and eyes so far to the left that you now have another, rapid involuntary eye movement getting involved. What is this called, and in which direction are your eyes moving? |
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Definition
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Term
| At what angle are the anterior and posterior canals aligned with one another? |
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Definition
| At approximately 45 degrees between the frontal and sagittal planes. |
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Term
| What is the “push-pull” system of the semicircular canals? |
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Definition
| Canals are paired (each of three canals on left side has a parallel counterpart on right side). When one canal is stimulated, the other is inhibited. |
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Term
| What is the most rapid type of eye movement possible? |
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Definition
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Term
| What type of acceleration stimulates hair cells in semicircular canals? |
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Definition
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Term
| What type of acceleration stimulates hair cells in otolith organs? |
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Definition
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Term
| Against what structure does fluid push against in the semicircular canals during rotational movement? |
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Definition
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Term
| Which reflex eye movement stabilizes images on the retina during head movement to preserve the image in the center of the visual field? Compared to the direction of movement, in which direction does this reflex work? |
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Definition
- VOR (vestibulo-ocular reflex)
- It works opposite to the direction of movement. |
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Term
| Is visual input required for VOR to work? |
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Definition
| No; it works even in the dark or with eyes closed. |
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Term
| To what parts of the brain does the vestibular system send signals? |
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Definition
| to the cerebellum and different parts of the cerebral cortex |
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Term
| How many otolithic organs are found on each side of the head? What are they called? What do they sense |
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Definition
Two
Utricle and saccule
Linear acceleration |
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Term
| How do otolithic organs work to detect linear acceleration? |
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Definition
| Otoconia crystals rest on a viscous gel layer beneath and are heavier than their surroundings. They are displaced in linear acceleration and deflect the ciliary bundles of the hair cells beneath, producing a sensory signal. |
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Term
| Does linear acceleration due to gravity cause otolith movement? |
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Definition
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Term
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Definition
equilibrium
stabilizes retinal imagery |
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Term
| What is the technical term for experience from the vestibular system? |
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Definition
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Term
| You are in an elevator and it starts to descend. Although your visual field remains constant, you can feel that you are moving downward. Which structures of the vestibular system are responsible? |
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Definition
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Term
| You are at the Medical School Christmas Gala and have just drunk WAY too much alcohol. Shortly after imbibing, the room starts spinning. What has happened? |
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Definition
| Your endolymph is denser than your blood due to a higher concentration of alcohol in the blood than in the vestibular system. |
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Term
| After several hours, your liver has begun clearing the alcohol out of your system. Strangely, your vertigo has now changed direction. What has happened to you now? |
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Definition
| Your endolymph is relatively dilute, as the alcohol concentration in your vestibular system is now higher than in your blood. |
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Term
| What are otoliths made of? |
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Definition
| calcium carbonate crystals |
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Term
| What is the sensory epithelium of the otolith organs called? |
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Definition
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Term
| What two types of layers lie over the hair cells of the otolith organs? |
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Definition
gelatinous layer
fibrous layer |
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Term
| What is the orientation of adjacent hair cells in the otolith organs? |
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Definition
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Term
| Does hair cell orientation change gradually or abruptly across the macula? What is the exception? |
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Definition
Gradually
The striola, where polarity is automatically reversed |
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Term
| What do the orderly transition of hair cell polarity across the maculae, and the curved surface of the maculae themselves, ensure? |
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Definition
| that all potential directions of linear acceleration are represented |
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Term
| What does the orientation of the utricular macula makes it most sensitive to? |
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Definition
| acceleration in the horizontal plane, and left- right static head tilt |
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Term
| What does the orientation of the saccular macula makes it most sensitive to? |
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Definition
| acceleration in the vertical plane, and front- back static head tilt |
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Term
| What is the sensory epithelium of the ampulla of the semicicular canals? |
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Definition
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Term
| What is the gelatinous mass within the ampulla of the semicircular canals called? |
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Definition
| cupula, where the cilia are embedded |
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Term
| If a person is seated rotating to the right, in which side of the head are the semicircular canals depolarized vs. hyperpolarized? |
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Definition
Right - depolarized; activated
left - hyperpolarized; inhibited |
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Term
| What is vestibular output relayed through? |
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Definition
| vestibular nuclei and spinal pathways to motor neurons controlling muscles of the neck (VCR) and limbs (VSR) |
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Term
| What conditions can exacerbate deficits related to vestibular damage? |
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Definition
| low light, uneven surfaces |
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Term
| Are saccade eye movements a part of the HVOR reflex or a result of them? |
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Definition
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Term
| What two types of tests are most often used to test vestibular function? |
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Definition
Caloric testing
Rotating (Barany) chair |
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Term
| What are rhytmic, oscillating movements of the eyeball, such as those caused by caloric testing and intoxication, called? |
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Definition
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Term
| What areas of the brain control nystagmus? |
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Definition
| areas of the mid and forebrain |
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Term
| How is the direction and velocity of the HVOR reflex compared to the direction and velocity of head movement? |
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Definition
| velocity is equal in magnitude to velocity of head movement, opposite in direction |
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Term
| Which nerve innervates the lateral rectus muscle? |
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Definition
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Term
| The apical membrane of hair cells in the vestibular system is also known as what type of "zone"? |
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Definition
| the sensory transduction zone |
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Term
| The basolateral membrane of hair cells in the vestibular system is also known as what type of "zone"? |
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Definition
| synaptic transmission zone |
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Term
| Which nerve innervates the lateral rectus muscle? |
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Definition
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Term
| In the HVOR pathway, which nucleus is responsible for inhibiting motor neurons innervating antagonistic muscles? |
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Definition
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Term
| In caloric testing, a patient is placed on his back. To what degree from the horizontal does the doctor need to tilt his head for the test to be effective? |
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Definition
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