module 6 chapter 46; ear, eye, taste, smell Flashcards
external ear components
auricles
canal
tympanic membrane
auricles
catch and funnel sound waves into ear canal
canal
somewhat S shaped from opening till tympanic membrane
protection from foreign objects and access to sound
glands along canal, secrete cerumen: coats hairs and prevents foreign bodies
tympanic membrane
thin, elastic, highly sensitive to changes in pressure
sound waves hit it and cause vibration
middle ear function
bony, air containing structure
sound energy is transmitted from air to fluids of inner ear
middle ear components
ossicles: attached to tympanic membrane
eustachian tube
ossicles
malleus (hammer)
incus (anvil)
stapes (stirrup)
eustachian tube
equalization of pressure against inner and outer surfaces of tympanic membrane.
has mucosal lining, extends form middle ear to nasopharynx
Inner ear components
oval window
cochlea
semicircular canals
cochlea
3 parallel tubes
- scala vestibuli (perilymph)
- scala media (endolymph)
- scala tympani (perilymph)
perilymph and endolymph
transmit mechanical vibrations from footplate of the stapes to the organ of corti
organ of corti
contains receptors for hearing, lies on basilar membrane
- has sensory hairs and supporting cells
- cells innervated by sensory fibers of vestibulocochlear nerve (VIII)
tectorial membrane
flexible flap of tissue over hanging the organ of corti
- hairs of sensory cells within organ of corti in contact
- wave of periphymph -> movement of basilar membrane -> pull or shearing of hairs across tectorial membrane
This action transforms mechanical energy of sound into electrical impulses stimulating CNVIII
ear and balance
sense organ of equilibrium
trigger of balance
activation of receptor hair cell in semicircular canals
- movement of head -> movement of endolymph in semicircular canals -> hair creates nerve impulse in vestibular portion of CNVIII -> transmitted to brain
vertigo
common symptom of vestibular disorder
- sensation of motion without movement or exaggerated sense of motion
vertigo s/s
N/V
pallor
sweating
nystagmus
causes of vertigo
common: peripheral vestibular cause
uncommon: CNS cause
disorders of brainstem or cerebellum
- tissue ischemia r/t atherosclerosis
- tumors
- psych disorders
- migraines
- multiple scerosis
vertigo tx
aimed at cause
antihistamines
anticholinergics
loss of hearing r/t occlusion s/s
none usually
insect: wing sounds and movement -> distress
pain
drainage
otosclerosis
localized, inflammatory disease of metabolism of endochondral bone of otic capsule
- abnormal removal of mature dense otic capsule bone -> replaced by bone with increased thickness -> progressive conductive, sensorineural, or mixed hearing impairment
otosclerosis and bone lesions
form around ossicles of middle ear - inner ear
- stapes: decreased transmission of sound waves
- cochlea: permanent sensorineural hearing loss
otosclerosis tx
surgically: preventative
stapedectomy: insert prostesis
conductive hearing loss
sound does not reach cochlea
sensorineural hearing loss
mechanism in inner ear disturbed, in cochlea or vestibulocochlear nerve to brain
presbycusis
age related hearing loss
sensory
metabolic
mechanical
sensory presbycusis
atrophy and degeneration of sensory and supporting cells
neural presbycusis
loss of neurons in cochlea and CNS
mechanical presbycusis
middle ear changes in properties -> conductive hearing loss
otitis media
inflammation of middle ear
almost always related to disfunction of eustatian tube, dx with presence of effusion
- more common in winter: URI
- children more susceptible: short, flexible, and horizontal eustachian tube
otitis media risk factors
pacifiers secondhand smoke reflux poor socioeconomic living daycare males natives eskimo craniofacial abnormalities
acute otitis media
sudden onset of ear pain associated with URI
acute otitis media s/s
pain children; - irritable - difficulty eating and sleeping - tugging - fever
otitis media tx
abx
pain relief
manage fever
surgical tubes with recurrent
chronic otitis media
inflammation of middle ear > 12 weeks irreversible damage - atrophy - perforation of tympanic membrane - adhesions - calcification of ossicles
chronic otitis media tx
surgical removal of debris from middle ear
tubes
adenoidectomy: help with eustachian tube function
vision requires 3 processes
formation of image on retina
stimulation of rods and cones
conduction of nerve impulses to brain
3 basic layers of eye
sclera
choroid
retina
sclera
white, opaque, made up of dense connective tissue
protects inner structure
maintains shape
clear portion: cornea
cornea
has greater curvature than rest of sclera, causing it to protrude.
canal of schlemm
deep in sclera, at conjunction with cornea
drains aqueous humor
ocular muscles are fixed to
sclera
choroid
highly vascularized, darkly pigmented
attached to iris; pigments responsible for eye color
iris
controls size of pupil
lens
behind pupil, is clear and avascular
elastic membrane, elasticity helps focus light stimuli on retina
anterior chamber of eye
filled with aqueous humor
drained by canal of schlemm
aqueous humor
anterior chamber of eye
provides O2 and nutrients to lens and cornea
continually formed and resorbed
- balance is total volume and pressure of intraoccular fluid.
posterior chamber of eye
portion behind lens
contains thicker fluid: vitreous humor
inner most layer of visual pathway
retinal layer: light waves turn into nerve impulses
several layers
2 types of photoreceptors: rod and curves
4 types of neurons: bipolar, ganglion, horizontal, amacrine
vision pathway steps retinal layer
photoreceptors synapses with bipolar cells then goes to ganglion cells
ganglion axons converge and leave eye in optic nerve
photoreceptor: rods
nighttime and peripheral vision
outnumber cones 20:1
photoreceptor cones
stimulated by relatively high intensity light responsible for color and visual acuity
- greater concentration in macula: responsible for detailed vision
horizontal and amacrine cells
modify transmission from photoreceptors to ganglion cells
sharpen and enhance responses of ganglion
Pigmented layer of retina
one cell thick: epithelium
removes metabolic cellular debris from photoreceptor cells
prevents new vessel growth into retina
absorbs light to diminish scattering -> enhanced vision
image on retina is
upside down and reversed left to right
- at optic chiasm nerve fibers cross over to other side
myopia
eye elongated, image focuses in front of retina rather than on it: fuzzy image
nearsightedness: corrected with concave lenses
unable to see distant objects clearly
hyperopia
eye shorter than normal, image focuses behind retina: fuzzy image
farsightedness: corrected with convex lenses
presbyopia
loss of accommodative capacity
inability to see near objects in middle age
corrected with reading glasses
astigmatism
irregular curve of cornea or lens -> distorted image
corrected with lens formed with opposite curvature
strabismus
cross-eyedness, condition of ocular misalignment
- abnormal neuromuscluar control of eyes
strabismus s/s
squinting frowning with reading closing one eye to see trouble picking up objects dizzy headache
strabismus tx
occlusion therapy: patching of good eye corrective lens surgery on eye muscles prisms exercises for eye
amblyopia
poor vision even with corrective lens in one or both eyes
most common cause of dec. vision in peds
results from: altered visual development despite normal appearing retinal and optic pathways
amblyopia tx
dx at earlier age is better
atropine to blur vision
patching of stronger eye
cataracts
clouding or opacity of lens
gradual painless, blurring of vision and eventual loss of sight.
by 80, 50- 70% of americans have cataracts
causes of cataracts
aging trauma: lens rupture and swlling congenital: downs, intrauterine rubella metabolic: DM, hypoparathyroidism systemic/inhaled corticosteriods cigarette smoking heavy ETOH
cataracts s/s
increased glare at night
one or both eyes
blurred vision
altered color perception
retinal detatchment
usually spontataneous could be secondary to - trauma - eye tumors - myopia - cataract extraction
3 categories of retinal detachment
exudative (serous)
tractional
spontaneous/ rhegmatogenous
exudative retinal detachments
results from accumulation of serous or hemorrhagic fluid in subretinal space
- sudden severe HTN
- inflammation
- neoplastic effusion
tractional retinal detachment
mechanical forces on retina caused by fibrosis or scarring pull it away
- injury or surgery to eye
- diabetic retinopathy
spontaneous/ rhegmatogenous retinal detachment
as people age vitreous humor decreases -> traction, causing separation
retinal detachment and vitreous fluid
fluid flows behind retina leading to traction and progressive detachment
retinal detachment s/s
sudden appearance of floating spots
odd flashes of light
blurry vision in single eye
“curtain pulled down”
diabetic retinopathy
disease of vasculature in retina
- capillaries lose ability to transport RBC -> hypoxia and decreased nourishment of retina
- vascular and neuronal degeneration, vascular leakage, macular edema, retinal neovascularization
2 categories of diabetic retinopathy
nonproliferative
proliferative
nonproliferative diabetic retinopathy
retinal veins become dilated and microaneurysms develop
- result of damaged vascular epilthelium
- small retinal hemorrhages and cotton-wool spots
early: visual changes minimun or resolves in few days.
progresses: retinal edema -> affected visual acuity
proliverative diabetic retinopathy
developments of new abnormal vessels caused by decreased retinal blood flow and ischemia
affects vision in 2 ways
- abnormal and prone to leak in the vitreous cavity -> vitreous hemmorhage
- firmly attach to retina and grow out into vitreous humor -> traction on retina -> detachment
diabetic retinopathy s/s
blurred, darkened, and distorted vision
changes in vision may fluctuate
some unable to read
age related macular degeneration (AMD)
leading cause of blindness among older adults
bilateral progressive degeneration with central vision loss
- decreased ability for O2 to diffuse to retinal pigment epithelium and photoreceptors -> release of growth factors and cytokines -
> growth of vessels into subretinal space
– new vessels leak -> distortion and reduction in clarity of central vision
may also result from cell death and atrophy of retinal pigment epithelium
AMD risk factors
age female smoing family hx increased cholesterol cardiovascular disease HTN obesity hx cataract surgery linked with oxidative stress and inflammatory chemicals
2 groups of AMD
dry (nonneovascular atrophic degeneration)
wet (neovascular or exudative)
dry AMD
most common
subretinal accumulation of cellular debris: drusen
metabolic dysfunction of retina
initially affects one eye, will spread to other
drusen
appear as discrete yellow deposits on retina on exam
wet AMD
visual loss more rapid onset
more severe visual disruption
impairment of barrier function -> subretinal collections of fluid -> retinal detachment or neovascularizations
AMD s/s
painless atrophic (dry): - slightly blurry vision - decreased fine detail - need more light exudative (wet): - progressive blurring - hallmark: wavy appearance of straight lines - vision may be lost rapidly or occur suddenly
Disorders of smell
decreased smell:
- smokers
- conditions involving congestion and swelling of nasal mucosa
- head trauma: loss of smell r/t shearing of the neuronal fibers
- tumors and large cerebral aneurysms of anterior cerebral and anterior communicating arteries
Olfactory hallucinations
- epilepsy and psych disorders
disorders of taste
decreased taste (gustatory)
- smoking; dryness of tongue and mucous membranes
- meds: antidepressant, antithyroid, antirheumatic, anticancer
- flu like illness
- lesions on thalamus and parietal lobe
disorders of taste and smell s/s
dec. smell often complains of dec. taste decreased appetite increased sugar, salt, and seasonings no reaction to strong smells do not notice body odor increased risk accident d/t not smelling gas/smoke increased ingestion of spoiled food
chronic open angle glaucoma
disease often bilateral
genetic component noted
no s/s in early stages
intraocular pressure consistently elevated
gradual loss of peripheral vision (tunnel vision)
retinal ganglion cell apoptosis -> axonal loss in optic nerve
optic disc atrophy
vague persistent dull eye pain,
inability to distinguish colors
halos around lights
acute angle closure glaucoma
- abnormal angle between the pupil and lateral cornea
- angle is narrow and blocks the outflow of aqueous humor when pupil is dilated
- rapid onset: can lead to medical emergency
- forward displacement of iris toward cornea with dilation harrows or closes changer angle
- rapid increase in pressure ->ischemia
- s/s:
- severe eye pain
- N/V
- blurred vision with halos
- redness of eye
- steamy cornea
- dilated pupil that is non-reactive to light
dx of glaucoma
intraocular pressure measurements
central visual field test
exam of optic disk
newborn vision
at birth: 20/400
by 6 month: 20/30
blink reflex, corneal reflex, and pupillary reaction to light
unable to coordinate head and eyes: dolls eyes reflex
shape of eyeballs, cornea, and lens changes with growth
stereopsis (depth perception) by 7 months of age
binocularity (perceived vision from both eyes simultaneously) begins at 6 weeks and established at 4 months.
geriatric vision
- decreased skin elasticity, changes in lacrimal gland function, and shrinking of vitreous body.
- changes to retina and lens -> decreased color vision and discrimination, reduced contrast sensitivity, and diminished accommodation
- retinal changes: loss of luteal pigment in macular areas
- > reduced light sensing of rods and cones
- development of presbyopia r/t decreased elasticity of lens and decrease in the effectiveness of the ciliary muscle. (inability to focus on near objects)
conductive hearing loss 4 mechanisms
obstruction
mass loading
stiffness
discontinuity
hearing loss obstruction
cerumen impaction most common
hearing loss mass loading
middle ear effusion
hearing loss stiffness
otosclerosis
hearing loss discontinuity
ossicular disruption
meniere disease
idiopathic
impairment of inner ear to regulate normal homeostatic systems
- production, maintenance, recycling of endolymph and perilymph
cause of meniere disease
autoimmunity allergies viral and bacterial infections head trauma chronic stress -men and women equally - usually in 50's
meniere’s s/s
episodic tinnitus
vertigo
sensations of ear fullness
fluctuating hearing loss
menieres tx
symptomatic relief - antiemetic, anticholinergics, low sodium diet smoking cessation management of stress dec. caffeine surgical interventions anti-migraine meds
