vestibular and visual systems
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52 terms
Terms | Definitions |
|---|---|
 the vestibular system is important for= | sensory information about head postion and movement, gaze stabilization and postural adjustment and balance |
| Gaze stabilization | the ability to focus on an object while the head is moving |
| vestibular apparatus consist of | 3 semicurcular canals and 2 otolithic organs |
| Semicircular canals | positioned at righ angles to each other, so there is one in each plane of motion |
| All 3 canals are connected on both ends to the | utricle |
| Each canal contains a swelling on one end called | the ampullae |
| the ampullae contains sensory hair cells that respond to | movement of fluid in the canals caused by acceleration or deceleration of the head in a rotational direction, |
| bending the hairs one way _______________ the frequency of signals sent by the vestibular nerve | increases |
| while bending hairs the opposite way _____________ the frequency | decreases |
| otolithic organs | includes the utricle and saccule |
| the utricle and saccule respond to | linear acceleration/deceleration, head postion relative to gravity |
| Each otolithic organ contains a sensory receptor called the | macula |
| The macula in the utricle and saccule are positioned at | 90 degree angles from each other, each macula contains hair cells suspended in a gelatinous fluid, resting on top of the fluid are sand like crystals calles otoconia |
| movement of the otoconia and gravity cause the hair cells to bend which= | changes the firing pattern of the vestibular nerve |
| muscles controlling eye movement | superior rectus (CN 3), Inferior oblique (CN 3), lateral rectus (CN 6), Inferior rectus (CN 3), superior oblique (CN 4), medial rectus (CN 3), Occulomotor (CN 3), Trochlear (CN 4), and Abducens (CN 6) |
| main purpose of eye movement | directing the eyes toward visual targets, gaze stabilization |
| directing the eyes toward visual targets includes | Saccades, smooth pursuits, vergence, and gaze stabalization |
| Saccades | fast eye movement that switch gaze from one target to another |
| Smooth pursuits | used for following a moving object |
| Vergence (Convergence or Divergence) | adjustments needed to focus on objects at different distances (medial/lateral eye movements) |
| Gaze Stabilizatin (visual fixation) is achieved by | vestibular-ocular reflex (VOR), because of connections between the vestibular nuclei and the nuclei of CN's 3,4, and 6, both eyes move opposite the direction of the head, important for stabilizing visual images while you are walking |
| Optokinetic reflex | elicited by moving objects in the visual field, influnces the perception of movement, (EX. sitting in a statonary car and car next to you moves IMAX |
| Optic nerve lesion | loss of vision in ipsilateral eye |
| optic chiasm lesion | bitemporal hemianopsia loss of lateral part of each visual feild |
| Optic tract lesion | homonomyous hemianopsia loss of contralateral part of each visual field |
| vertigo | an illusion of movement this is the most common symptom |
| Nystagmus | involuntary back and forth movements of the eyes, named by the direction of saccadic eye movements (Ex. right-beating nystagmus) |
| Nystagmus can be a normal respones with | stimulation of the semicircular canals using rotation or temperature changes or with maximal lateral movement of the eyes |
| Disequilibrium (imbalance) | overload of visual stimuli causes disequilibrium and disorientation |
| Ataxia | must be differentiated from cerebellar and sensory ataxia |
| peripheral vestibular disorders are caused by | damage to the vestibular apparatus or the vestibular nerve |
| Peripheral vestibular disorders include | BPPV, vestibular neuritis, Meniere's disease, tramatic injury, perilymph fistula and damage to the vestibular apparatus by certain drugs (gentamicin and streptomycin) |
| BPPV definition | Benign=not malignant, Paroxysmal=sudden onset, Positional=provoking stimulus is head position, Vertigo=this is the main symptom |
| Etiology and onset of BPPV= | displacement of otoconia from the macula into a semicircular canals, may occur spontaneously or due to trama or infection |
| signs and symptoms of BPPV= | rapid head movements cause vertigo and nystagmus that subside in less than 2 minutes, problems when getting into/out of bed, turning in bed, bending over to pick something up or reaching upward to get something on a high shelf |
| Diagnosis of BPPV | in the clinic with the Hallpike-Dix maneuver |
| Treatment of BPPV | Canalith repositioning maneuver (dislodges the otoconia from the semicircular canal) |
| Vestibular Neuritis | inflammation of the vestibular nerve |
| Etiology and onset of Vestibular Neuritis | usually due to a viral infection |
| Signs and symptoms of Vestibular neuritis | disequilibrium, spontaneous nystagmus, N/V and severe vertigo |
| Treatment of Vestibular neurtits | meds are used to suppress N/V and vertigo until infection resolves |
| Menire's disease | increased pressure in the inner ear |
| Etiology and onset of Menire's disease | no known cause, pt. experiences a variable pattern of attacks and remission |
| Signs and symptoms of Menire's disease | Tinnitus, vertigo,N/V, hearing loss and a sensation of fullness in the ear |
| Treatment of Menire's disease | Vestibular suppressants, diuretics, and occasionally surgery |
| Perilymph Fistula | fluid (perilymph) leaking out of the inner ear into the middle ear |
| Etiology and onset of Perilymph fistula | abrupt onset, usually caused by trauma |
| signs and symptoms of Perilymph fistula | tinnitus, hearing loss and vertigo |
| treatment of Perilymph fistula | treated conservatively with bedrest, surgery is performed if conservative treatment fails |
| Etiology and onset of Central Vestibular Disorders | stroke, tramatic brain injury, brain tumor, multiple sclerosis or migrains HA's |
| Signs and symptoms of Central Vestibular disorders | usually milder than peripheral disorders, accompanied by other signs of brainstem damage such as sensory loss, motor loss, double vison, dysarthria, distorted perception of vertical causing them to tilt their head, push sideways when sitting or standing (lateropulsion), if the VOR is disrupted, objects will appear to bounce when walking (oscillopsia) |
| treatment of Central Vestibular disorders | Physical therapy exercises help with habituation and or adaptation of the nervous system |
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