Vestibular System
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42 terms
Terms | Definitions |
|---|---|
 What are the functions of the vestibular system? | Provides the unconscious with a sense of orientation in space, specifically allowing us to stabilize posture and visual fields, and to control autonomic function, such as blood pressure. |
| How many semicircular canals are there? | Three: anterior, posterior, and lateral. |
| Does endolymph connect cochlear duct, saccule, utricle, and semicircular canals? | Yes. |
| What ion is concentrated in endolymph? | Potassium. |
| What type of accelaration does endolymph sense? | Angular accelaration. |
| What is perilymph? | CSF-like fluid that surrounds membranes in inner ear. |
| What is cupula? | Thickened endolymph nex to crista/hair cells in the ampulla that blocks circular endolymph flow. |
| What are the two types of cilia in semicircular canals? | Kinocilia, i.e. true cilia, attached to stereocilia. |
| How are vesicles released from hair cells? | Mechanical stimulation opens K channels, depolarize cell, and open Calcium channels. Calcium-dependent potassium channels re-hyperpolarize the hair cells. |
| Does a rightward turn of the head, pushing endolymph onto the cupula of the right lateral semicircular canal, straighten or bend the kinocilia? | Bend, opening K channels. It straightens the cupula on the left, closing K channels. |
| How does the vestibulo-ocular reflex stabilize visual fields? | A rightward turn of the head activates the right lateral semicircular canal, causing the eyes to move to the left. |
| Why does per-rotatory and post-rotatory nystagmus develop? | Eye can't keep moving as acceleration continues, and so resets to the midline, with the fast phase direction corresponding to the direction of the nystagmus. |
| How is nystagmus named? | By the fast phase, so a rightward rotation causes leftward eye movement, a rightward fast phase reset, right per-rotatory nystagmus and left post-rotatory nystagmus. |
| Why does direction of nystagmus switch after rotation stops? | Maximal deceleration equivalent to opposite turn, patient will attempt to prevent deceleration by continuing turn, falling and past-pointing in direction of original turn. |
| What nystagmus will display with irrigation of the right lateral semicircular canal with (1) supine patient and warm water irrigation or (2) prone patient and cold water irrigation? | Rightward nystagmus, i.e. mimicking of rotation to the right, as both cases will cause . |
| Which direction will a patient fall and past-point if vestibular system fooled to believe is rotating to the right? | Left. Patient will attempt to stop rotation. |
| Which direction will a patient's visual fields move if vestibular system fooled to believe is rotating to the left? | Visual fields/eye move right, i.e. objects in field move to the the left, i.e. left post-rotatory nystagmus. |
| Which one of the three canals is in an anatomical plane? | The horizontal is about 20 to 30 degrees above the horizontal, while the other two are at about 45 from the saggital. |
| What are the otolith organs? | The utricle and the saccule. |
| To what do the otolith organs connect? | The beginnings of the cochlear duct. |
| What are the otoconea? | Calcium carbonate crystals inside thickened endolymph, attached to kinocilia. |
| In which plane is the utricular macula? | Horizontal = horizontal acceleration. Utricle has short vertical axis and long horizontal axis. |
| In which plain is the saccular macula? | Vertical = vertical acceleration. Saccule has short horixontal axis and long vertical axis. |
| What is the striola? | Line within macula that orients kinocilia so that macula primed to detect fluid movement in either direction. |
| Are the otolith organs sensitive to gravity even without movement? | Yes! They are not just sensitive to linear acceleration due to gravity, but also to linear forces like gravity that do not produce movement. |
| What are three otolithic reflexes? | Ocular counterrolling, righting reflex, and vestibulo-sympathetic reflexes. |
| Which vestibular nuclei receive input from the semicircular canals? | Superior and medial vestibular nuclei. |
| Which vestibular nuclei project bilaterally to the oculomotor nuclei? | Superior and medial vestibular nuclei. |
| Which vestibular nucleus projects to the thalamus and forms a contralateral commissure? | Medial vestibular nucleus, which also receives input from the semicircular canals. Medial also projects to spinal cord, primarily cervical portion. |
| Which vestibular nucleus receives input from the cerebellar cortex? | Lateral vestibular nucleus. |
| Which vestibular nucleus projects to spinal cord and controls extensor muscles of posture? | Lateral vestibular nucleus. |
| Which vestibular nuclei projects to cerebellum? | All! |
| Which vestibular nucleus receives input from the otolith organs? | The inferior vestibular nucleus. |
| Which vestibular nucleus only has output to the cerebelllum? | The inferior vestibular nucleus. |
| What causes benign paroxistic positional vertigo? | Calcium deposits or other debris in semicircular canals. |
| Does the lateral medullary syndrome cause vertigo? | Yes, but because central lesion, also causes other central deficits. |
| Can peripheral vestibular dysfunction be suppressed by visual fixation? | Yes. |
| Does peripheral vestibular dysfunction keep company with hearing deficits or tinnitus? | Yes. |
| To which direction does peripheral vestibular dysfunction have nystagmus? | Yes, to opposite side. |
| To which direction does vestibular dysfunction elicit head tilt? | To ipsilateral side? |
| Which form of vestibular dysfunction is indicated by mixed horizontal and torsional nystagmus, peripheral or central? | Peripheral. |
| Which form of vestibular dysfunction is indicated by pure vertical or torsional nystagmus? | Central. |
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