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What are the functions of the Vestibular System
- 1. Provides information about the position and movement of the head
- 2. Stabilizes head movements
- 3. Coordination of head and eye movements, and body posture
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What are the three main inputs for spatial orientaion
- Visual
- Proprioceptive
- Vestibular
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What is car sickness a result of physiologically
This happens when there is sensory conflict such as the eyes are saying that there is no movement, but the vestibular system is sensing movement
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What are the receptor organs in the vestibular system
- Cristae Ampullares
- Maculae (Utricle and Saccule)
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What do the Utricle and Saccule sense
Linear acceleration
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What do the Cristae Ampullae sense
Angular acceleration
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In the vestibular system when are action potentials being sent at a higher rate
When the hair cells are becoming depolarized by the movement of the stereocilia towards the Kinocilium
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What causes the hair cells in the Vestibular system to hyperpolarize
When the stereocilia are leaning away from the Kinocilium
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The movement of what moves the cilia in the cupula
Endolymph
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When the head moves, what way does the endolymph move
The Endoloymph moves in the opposite direction as the head rotation
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What is the most important force working on the Macula
Gravity
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Why doesn't the otolith membrane move by the movement of the endolymph
- Its higher density prevents the movement by the endolymph
- Gravity will move the otolith as a result of a head tilt
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Displaced otoconia
- a.k.a. Vertigo
- Can follow head trauma
- In some it is benign
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Benign paroxysmal positional vertigo
- Brief episodes of vertigo typically related to changes in position
- Results from the displacement of the otoconia in the semicircular canals that push the cupula
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What are the branches of the Vestibular nerve
- Post. Ampullary
- Saccular
- Utriculoampullary (utricle, anterior, and lateral ampullary)
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Acoustic neuroma
Damage to the Vestibular portion of the vestibularcochlear (XIII) nerve causing vertigo, loss of balance, and an unsteady gait
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What is the most common place of damage that results in Acoustic Neuroma
Pontocerebellar angle
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What happens when the cochlear nerve is damage
Loss of hearing and Tinnitis
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What can be potentially damaged in a large acoustic neuronima (Neuroma)
- CN; V, VI, VII, VIII, IX, X, XII
- Cerebellum
- Pyramidal tract
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Wallenburgs syndrome will display what symptoms (PICA syndrome)
- Hoarseness of voice & Difficulty swallowing (Nucleus Ambiguus)
- Miosis & Ptosis (Sympathetic)
- Reduced feeling in face (Descending tract of V)
- Vertigo & Nystagmus (Vestibular nucleus)
- Unsteady gait (Inferior cerebellar peduncle)
- "The symptons I have when I go to Wally world!"
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What are the afferent vestibular connections
- Vestibular nerve
- Cerebellum (Flocculonodular lobe)
- Spinovestibular (proprioception)
- Visual info
- Reticular formation
- Commissural fibers
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What are the efferent vestibular connections
- Occulomotor, Abducens, Trochelar nuclei
- Cerebellum
- Spinal cord
- Reticular formation
- Thalamus
- Hair cells (Efferent)
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What causes the stabilty of the information taken in from head movements and eye movement from activities like walking or driving on a bumpy road
Vestibulo-ocular reflex (VOR)
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How does the vestibulo-ocular reflex (VOR) react to a turn of the head to the left
- Left semicircular canal excitation
- Rt Abducens nuclei (VI) flexes lat. rectus muscle of rt eye
- Left Occulomotor nucleus (III) flexes the medial rectus of the left eye
- Other side inhibits
- Eyes turn to the right for a forward gaze
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What fascicle connects the vestibular and eye muscle nuclei in a vestibulo-ocular reflex (VOR)
Medial longitudinal fascicle
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Nystagmus
Involuntary alternating eye movements
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How can one induce nystagmus without sophisticated equipment
By irrigating the ear with cold or warm water
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What effects does warm or cold water injected into the ear do
- Cold - induces nystagmus away (Opposite) form the irrigated ear
- Warm - induces nystagmus to the Same side
- "COWS"
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Lateral vestibular tract is important for
Antigravity muscles mainly ipsilateral extensors
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Medial vestibular tract is important for
Mainly head and neck coordination
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Over stimulation of the vestibular nerve can cause what symptoms
- Nausea
- Vomiting
- Sweating
- Changes in cardiovascular and respiratory functions
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A lesion to the left vestibular nerve would cause what
Stumbling to the left
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Menieres disease
- High endolymphatic pressure effecting both cochlear and vestibular functions
- Recurring episodes of vertigo accompanied by progressive hearing loss
- "What Jane Eyre causes in Men"
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True Vertigo
Spinning sensation
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Vestibular neuritis
- Infection/inflammation of Scarpa's ganglion or the nerve
- Intense vertigo for several days
- Unsteadiness lasting weeks/months
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The sacculus has what feature that makes it effective for testing
It is sensitive to sound waves as well making the pathway visibly in tact by innitiating movement in the sternocleidomastoid muscle by stimulating it with sound
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Scarpas ganglia is used for what nerve
Vestibular nerve only
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