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Neuro Assessment 6
Hearing and Vision
79
Anatomy
Graduate
09/28/2011

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Cards

Term
Transduction of Sound
Definition
Sound wave-->Air-> External auditory canal -> Tympanic Membrane -> Moves malleus -> Incus -> Stapes -> Inner Ear Pressure change -> Triggers wave in basilar membrane of Cochlea -> Bends Receptor Hairs
Term
Where do high Frequency tones displace hair?
Definition
near Base of Cochlea
Term
What happens as tones get lower?
Definition
Point of maximal membrane displacement moves toward the cochlear
Term
What is Conductive Hearing loss?
Definition
Transmission of sound through air is blocked. Can still hear through bone CONDUCTION
Term
What are some causes of Conductive hearing loss?
Definition
Wax, foreign object, otitis externa, tympanic membrane perforation, otosclerosis
Term
What is Sensory hearing loss?
Definition
Disorders of the cochlea, cochlear nerve, central pathways
Term
What are some causes of Sensorineural hearing loss?
Definition
Congenital, Presbycusis, Viral, ototoxicity, trauma, Meniere's disease, vestibular schwannomas
Term
What can cause Mixed hearing loss?
Definition
otosclerosis, temporal bone fractures, chronic middle ear infections, middle ear tumors and some inner ear malformations
Term
What are the sypmtoms of Meniere's disease?
Definition
Vertigo, fluctuating sensorineural hearing loss and tinnitus
Term
How is Meniere's Disease Treated?
Definition
Low salt diet and diuretics
Term
What is the pathophysiology of Meniere's disease?
Definition
an increase in volume and pressure of the endolymph of the inner ear
Term
During a clinical assessment of hearing loss what do you want to inquire about?
Definition
Duration, change over time, associated symptoms, vertigo, earache, family Hx
Term
If Bone conduction is greater than air conduction in the Rinne Test, the patient has what?
Definition
Conductive Hearing loss
Term
What are the results of the Rinne and Weber test in someone who has Sensoriheural hearing loss?
Definition
Rinne: Air conduction greater than Bone Conduction in Both ears
Weber: Sound Louder in Normal Ear
Term
In a conductive hearing loss, the sound will lateralize to which ear?
Definition
to the affected ear
Term
What disease is associated with an audiogram pattern that results in a greater threshold elevation in the lower frequencies?
Definition
otosclerosis - caused by fixation of the footplate of the stapes
Term
What does the typmanogram measure?
Definition
impedance of the middle ear to sound
Term
What would an audiogram show for middle ear effusions?
Definition
greater elevation of thresholds in Higher frequencies
Term
What does Sensorineural hearing loss look like on audiogram?
Definition
steadily rising threshold elevations with increasing frequencies - (the higher the frequency the worse the hearing)
Term
What does noise induced hearing loss usually show?
Definition
selectively greater loss at 4000Hz
Term
What are the characteristics of Otosclerosis?
Definition
Conductive Hearing Loss, progressive sensorineural, starts in 20-30s, Bilarteral, +Family Hx
Term
What does a patient typically present with if they have a vestibular schwannoma?
Definition
Sensorineural hearing loss, NO Vertigo
Term
What are the cardiac causes of syncope?
Definition
cardiac arrhythmias, heart failure, obstuction of cardiac outflow, pulmonary embolism
Term
What is Vertigo?
Definition
an illusion of movement typically described as spinning of whirling
Term
What is True Vertigo?
Definition
Disease of the vestibular system, peripherally or centrally
Term
What is the clinical sign of vertigo?
Definition
Nystagmus
Term
What monitors the position of the head in space by detecting angular, static and linear acceleration?
Definition
Vestibular system
Term
What part of the vestibular system detects linear motion and gravity?
Definition
Sacculus and Utricle
Term
How are the Sacculus and utricle alined?
Definition
sacculs-coplaner with vertical axis
utricle-coplaner with the horizontal axis
Term
What detects angular movements?
Definition
Semicircular canals
Term
What are otoliths?
Definition
crystals of calcium carbonate on top of the gelatinous matrix that the sensory heair cells of the saccule and utricle
Term
How does the distortion of the hair cell produce a signal in the vesitibule?
Definition
Force on Kinocilium -> opens (or closes) K+ channels on other cilia -> depolarizes cell membrane -> activates Ca+ channels -> Ca+ influx -> Neruotransmitter released
Term
How is the signal from the vestibule regulated?
Definition
Force Toward Kinocilium -> Increases Neurotransmitter release -> activates afferent fivers from Scarpa's ganglia
Force Opposite Kinocilium -> Decreases neurotransmitter -> decreases impulses
Term
Where do the bodies of the sensory nerve fibers at the hair cells base lie, and where do they project to?
Definition
Scarpa's ganglion, Brainstem via vestibular nerve
Term
How do the kinocilium face in the utricle?
Definition
toward a midline valley called the striola
Term
What two kinds of forces with alter the firing rate in the Utricle?
Definition
Linear force within the plane of the utricle
Static gravitational force when the plane is tilted
Term
How is the kinocilia oriented in the saccule?
Definition
away from the striola
Term
If you stand in an elevator that starts to move up what part of the saccula is activated?
Definition
lower part
Term
How are the hairs oriented in the ampulla?
Definition
one direction
Term
A net increase in firing from the left vestibular apparatus will cause the eyes to move which way?
Definition
Right
Term
How can you "Rule In" psychogenic unresponsiveness as the cause of coma?
Definition
demonstrating that ice water in either ear induces nystagmus
Term
If a patient requires saccadic refixation with head thrust maneuver to the left, where is there a lesion?
Definition
left vestibular lesion
Term
In the Dix-Hallpike maneuver, how do you maximally stimulate the right posterior canal and maximally inhibit the left anterior canal?
Definition
Turing the head Right and falling back from a sitting to lying position
Term
How is Peripheral vertigo with nystagmus chararcterized?
Definition
Latency of onset
subsides over 1-2 min
Nystagmus increases with gaze away from lesion
mixed horizontal-torsional
Habituates with repetition
Term
How is Central vertigo with nystagmus characterized?
Definition
No latency of onset
Sustained with position (does not improve with visual fixation)
No increase, may change direction with chage of gaze
Single Plane nystagmus
Does Not Hapituate
Term
What is Benign paroxysmal positional vertigo (BPPV) and what causes it?
Definition
Peripheral Vertigo, Otoconia break free and collect in the posterior semicircular canals, causes greater distortion of the cupula in the ampulla then there really is.
Starts 5-10 seconds after head movement, lasts 30-45 seconds
Term
What is the most common cause of vertigo (especially in the elderly)?
Definition
Benign Paroxysmal Positional Vertigo
Term
What type of vertigo is often triggered by looking up as they reach for a high shelf?
Definition
BPPV
Term
What is a less common cause of BPPV where particles reach the cupula?
Definition
Cupulolithiasis
Term
What is one of the posterior canals functions?
Definition
To maintain visual fixation via the vestibulo-ocular reflex
Term
If the right posterior canal is occluded, What will the Dix-Hallpike maneuver show?
Definition
Head turned Right, Eyes Looking Left, causes upbeat vertical hystagmus in plane of Rt. Post. Semicircular canal, if patient looks right, corrective movement becomes torsional
Term
What's the course light takes to get to the fovea?
Definition
Refracted by cornea-> inverted through pupillary opening-> refracted by the lens-> Projected on the fovea
Term
What protects the Retina and Choroid?
Definition
Sclera
Term
What is the Choroid?
Definition
vascular layer for retina
Term
How is the visual axis maintained on the fovea?
Definition
Extraocular muscles
Term
What provides a barrier from the retina to the choroid?
Definition
Pigment Cells
Term
What is the Retinal pathway of cells?
Definition
Photoreceptors to bipolars to ganglion cells
Term
What are the 2 interneurons of the retina called?
Definition
Horizontal cells and amacrines
Term
What cells coalesce to form the optic nerve head, Blind Spot?
Definition
Ganglion Cells
Term
What layer of the retina absorbs light?
Definition
Retinal Pigmented Epithelium - contains melanin
Term
What are the 2 main functions of the Retinal pigmented epithelium?
Definition
Seperate the choroid from the retina, Phagocytosis of rod outer segments
Term
What processes black and white info?
Definition
Rods
Term
Where is light detected and transduced by the rods?
Definition
Outer segment
Term
How often are rod outer segments phagocytosed?
Definition
every 10 days
Term
What photoreceptors process color?
Definition
Cones
Term
What are the 3 types of Cones?
Definition
L-cones - long wavelengths
M-cones - medium wavelengths
S-cones - short wavelengths
Term
What cones represent blue? Green? Red?
Definition
Blue - S-Cones
Green - M-cones
Red - L-cones
Term
Why are men often red-green color blind?
Definition
M- and L- cones are carried on X chromosome
Term
What kind of response do cones and rods have with the stimulation of light?
Definition
Hyperpolarization
Term
How is rhodopsin activated?
Definition
Light absorption converts 11-cis-retinal to all-trans-retinal which activates rhodopsin
Term
What does Transducin dissociate into after GDP is replaced by GTP?
Definition
Talpha-GTP and T-betagamma
Term
What activates cGMP phosphodieterase?
Definition
Talpha-GTP
Term
How do the cation channels re-open?
Definition
efflux of Ca+ reduces cytosolic Ca, inhibits PDE -> cGMP levels rise toward pre-stimuls levels
Term
How is Rhodopsin reactivated?
Definition
RK phosphorylates "bleached" rhodopsin, Arrestin binds, inactivating rhodopsin, slowly arrestin dissociates, rhodopsin is dephosphorylated, all-trans->11-cis
Term
What do horizontal cells do?
Definition
help converge the signals from multiple rod photocells to fewer Rod Bipolar cells. (same for cones)
Term
What are transient ischemic attacks affecting the vision of one eye usually caused by?
Definition
platelet thrombin emboli from atheromatous plaques in the carotid artery on the same side
Term
What symptom would you suspect basilar artery insufficiency?
Definition
transient loss of vision in both eyes simultaneously
Term
What are some examples of painless loss of vision?
Definition
cataract, central retinal artery or vein occlusion, retinal detachment
Term
Pain on eye movement accompanied with loss of central vision and a relative afferent pupillary defect are common in what?
Definition
optic neuritis
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