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34 Cards in this Set
- Front
- Back
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Main functions of vestibular system |
Receptors of system:
-Detect motion & spatial position of the body -Transduce and encode this information into neural signals -And send to brain |
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What does brain do with neural info from vestibular system? |
-Processes it into a uniform signal about direction, speed of motion, and position of head in space -Combines this signal with info from other systems to coordinate visual gaze, balance, spatial orientation, and autonomic responses |
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2 main parts of vestibular system |
-Otoliths -Membranous Semicircular Canals (both of are part of Membranous Labyrinth) |
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Which fluid is in the vestibular system? |
-Endolymph |
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Maculae & Cristae together are known as.... |
-The sensory end organs of the vestibular system |
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Names of Otoliths |
-Utricle -Saccule |
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Location/Relative Position of Otoliths (6) |
-Located inside vestibule of bony cochlea -Utricle sits in elliptical recess -Saccule sits in spherical recess -Connect to each other via endolymphatic duct -Saccule connects to cochlear duct -Utricle connects to SCCs |
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Overall function of Otoliths (3) |
-Sense linear acceleration (walking, falling, vehicular travel) and position of head in space -House maculae |
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Maculae: definition and # |
-Sensory organs in otoliths -Singular: macula -4 maculae total: 2 per ear -One macula in utricle, one macula in saccule |
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Maculae in utricles respond to what kind of movement in particular? |
-Horizontal movement of head -(Shaking head 'no') |
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Maculae in saccules respond to what kind of movement in particular? |
-Linear acceleration (being in a car) -Vertical tilting of the head (shaking head yes) |
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Structures of maculae (6) |
-Otoconia -Otolithic membrane (gelatinous layer) -Cilia of hair cells (stereocilia + 1 kinocilium per hair cell) -Hair cells -Support cells -Afferents of vestibular nerve |
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Otoconia: definition & function |
-Crystals of calcium carbonate that sit on top of gelatinous otolithic membrane -Add weight to the gelatinous otolithic membrane, making it sensitive to gravity and intertia |
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Otolithic membrane: definition |
-Gelatinous membrane found in maculae -Is covered/weighted with otoconia -Has cilia projecting into it from below |
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Kinocilium: definition |
-The single longest cilia at the apical portion of a hair cell in an otolith -In macula: embedded in the gelatinous otolithic membrane (along w/stereocilia) -In crista: embedded in cupula (along w/stereocilia) |
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Kinocilia: function |
-Bending of stereocilia towards or away from a kinocilium will cause depolarization or hyperpolarization of its hair cell (depending on the direction). |
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Physiology of Maculae (3 steps) (see slide Transduction of Linear Acceleration) |
Change in linear acceleration or head position: 1. Causes gelatinous otolithic membrane (weighted down by otoconia) to move 2. Bends embedded stereocilia 3. Depolarizes hair cells & stimulates afferent fibers of vestibular branch of CN VIII. |
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Physiology of Maculae (Extra details from 305 slides, for context) |
1. When otolithic membrane moves in response to changes in position/acceleration: 2. Bends stereocilia either towards or away from kinocilium; 2a. Bend towards kinocilium --> depolarizes hair cells & stimulates afferent fibers of vestibular branch of CN VIII or 2b. Bend away from kinocilium --> hyperpolarizes hair cells & inhibits afferents of vestibular branch of CN VIII |
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Overall function of SCCs (3) |
-Detect angular acceleration (rotational movement, head turns) of head -Each canal detects movement in a single, specific plane |
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Anterior SCC: detects movement in which plane? |
-Horizontal movement -(Shaking head 'no') |
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Posterior SCC: detects movement in which plane? |
-Vertical plane -(Nodding head yes) |
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Horizontal SCC: detects movement in which plane? |
-Rotational -(Spinning) |
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Ampullae: definition and location |
-Enlarged sacs at the end of each semicircular duct
-Contain cristae |
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Cristae: definition and # |
-Sensory organs in SCCs -Epithelial cells that run along base of ampullae -Singular: crista -6 cristae total / 3 in each ear -(One crista in each SCC) |
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Structures of cristae |
-Cupula -Hair Bundles/Cilia (Sterocilia + Kinocilium) -Hair cells -Supporting cells -Vestibular nerve fibers |
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Cupula: defintion & function |
-Gelatinous membrane attached to top and bottom of ampulla -Has cilia embedded in it (stereocilia + kinocilia) |
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Cristae respond to what kind of movement in particular? |
-Changes in velocity of rotatory movement of head -(Think of spinning ice skater) |
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Physiology of Semicircular Canals |
When head rotation occurs: 1. Endolymph in SCC moves opposite of the rotation, but lags behind because of inertia 2. Moving endolymph causes cupula to bend (deflection) 3. Bending of cupula --> bending of cilia --> 4. Hair cells depolarize and stimulate fibers of vestibular nerve |
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Physiology of Semicircular Canals (Extra detail from 305 slides, for context) |
What happens when rotational movement slows down? -Endolymph will keep moving in direction of the rotation -Cupula gets bent in the opposite direction from acceleration and so do cilia -Hair cells hyperpolarize and inhibit fibers of vestibular nerve. |
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One common pathology of the Vestibular System? |
Postional Alcohol Nystagmus (PAN) |
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Postional Alcohol Nystagmus: what is it? |
-Pathology of the vestibular system that causes vertigo when you drink -There is PAN1 and PAN2 |
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PAN 1 vs. PAN 2: which is which? |
-PAN 1 is the spins while drinking -PAN 2 is dizziness the next morning |
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What happens during PAN 1? |
-Alcohol affects blood supply of the cupula -Lowers its density relative to endolymph -Cupula starts to float in the endolymph -Causes depolarization and afferent signals to the brain (tells it that you are spinning) |
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What happens during PAN 2? |
-Density of cupula returns to normal -But density of endolymph 'catches up' -Endolymph has more alcohol content and is now less dense than normal -Cupula sinks and the spinning returns -Will not return to normal until blood and endolymph equilibrate to normal density |
