15.2-15.4 Eye/Ear Physiology Flashcards
Packets of energy (photons) that travel in wavelike fashion at high speeds
Visible light can be broken up into bands of colors
Color that the eye perceives is a reflection of a particular wavelength
Light
How does light travel?
Straight lines
Blocked by transparent objects
Seeing black; seeing white
Lack of reflection (absorbs all color); all reflection (no absorbtion)
Bending of light rays; Due to speed of light when it passes from one transparent medium to another and path of light is at an oblique angle
Refraction
Good at refracting light because they are curved on one or both sides
Disc part of eye
Lens
Thicker in center than edges
Bend light passing through it, so that rays converge at a single point (focal point)
More convex the lens, more light that bends, shorter focal distance
Convex
Thicker at edges than in center
Disperse light
Concave lens
Image is _____ and ______ but brain corrects it in light refraction
Upside-down; backwards
Cornea –> Aqueous humor–> Lens–> Vitreous humor–> Neural layer (retina)–> Photoreceptors
Pathway of light
Light is refracted ____ times
3
Entering cornea, Entering lens, Leaving lens
Part of eye where majority of refractory power is
Constant, cannot change focus
Cornea
Eyes are best adapted for this type of vision
Ciliary muscles completely relaxed
Lens flattened from pulling on ciliary zonules
Distant vision
State of vision where a faraway object at infinity is in sharp focus with the eye lens in a neutral or relaxed state
Normal eye
Emmetropia (normal)
Changing of lens shape to increase refraction (focusing)
Ciliary muscle contracts, zonules loosen, lens bulges
Accommodation of the lens
Constriction of pupils to prevent most divergent light rays from entering eye
Sphincter pupillae accomplish this
Constriction of pupil
Medial rotation of eyeballs causes convergence of eyes toward object being viewed
Convergence of eyballs
Normal eye
Emmotropic eye
Eyeball is too long, so focal point is in front of retina
Corrected with concave lens
Myopia (nearsighted)
Eyeball is too short, so focal point is behind retina
Corrected with a convex lens to converge light stronger
Hyperopia (farsighted)
Unequal curvatures in different parts of the cornea
Causes smeared look in lights especially at night
Corrected with cylindrically ground lenses or laser procedures
Astigmatism
Loss of accommodation over 50
Presbyopia
Modified neurons involved in vision (type of receptor)
Includes rods and cones
Photoreceptors
Light recieving region of photoreceptors
Plasma memebrane of outer segment folds back to form many discs
Dics contain visual pigments that change shape when absorbing light
Outer segment
Site of metabolism and maintenance of membrane potential in photoreceptor
Inner segment
Consist of retinal combined with proteins called opsins
Visual pigments
Key light absorbing molecule
Synthesized from vitamin A
Absorbs different visual wavelengths depending on which opsin it is bound to
Retinal
4 opsins only in rods
Rhodopsins
3 opsins found in cones
Names are based on colors they absorb best
Green, blue, red
Require bright light for activation
React more quickly than rods
Less sensitive than rods
Non Converging pathways occur here
Cones
We see dimly lit objects best we do not look at them directly and they are _________
Moving
Lack of one or more cone pigments
Inherited as an X-linked condition, more common in males
Common type = red-green
Color blindness
Process by which light energy is converted into a graded receptor potential (5 part relay race)
Begin when a visual pigment captures a photon of light
Retinol is bent from dark, but straightens out when light is present
Phototransduction
When moving from darkness into bright light we see a glare
Both rods and cones are on, pupils contrict
Improves over 5-10 minutes
Light adaptation
When moving from bright light into dim light, we see blackness
Cones stop functioning
Rods are off
Pupils dilate
Increases sensitivity over 20-30 minutes
Dark adaptation
Condition in which rod function is seriously hampered
Driving at night is impaired
Nyctalopia
Pressure disturbance produced by a vibrating object and propagated by molecules of the medium
Sound
Created when an object moves; Creates areas of high pressure and low pressure (compressions and rarefactions)
Sound waves
An area of low pressure due to presence of fewer air molecules
Rarefaction
Number of waves that pass given point in a given time
Perceived as a pitch
Most sounds are mixtures of different frequencies
(High pitched vs. low pitched)
Frequency
Height of wave crests
(Loud vs. soft)
Amplitude
Reception of an air sound wave that is converted to a fluid wave that ultimately stimulates mechanosensitive cochlear hair cells that send impulses to the brain for interpretation
Hearing
Higher the intensity, the _____ vibration
Higher
Typanic membrane is _______ times larger than oval window, so vibration transferred to oval window is 20x amplified
20
Sound waves end here and bulges outward into middle ear cavity
Round window
Blocked sound conduction to fluids of internal ear
Causes include impacted wax, perforated eardrum, otitis media, otosclerosis of the ossicles (fusing)
Conduction deafness
Damage to neutral structures
Typically from hair cell loss: Gradual loss of cells throughout life
Single explosive loud noise, or prolonged exposure to high intensity sounds
Sensorineural deafness
Helps to collect sound and direct it into auditory canal
Ear trumpet
Amplifies sound, has a microphone, amplifier, and speaker
Hearing aid
Convert sound energy into electrical signals
Are effective for congenital or age/noise cochlear damage
Cochlear implants
Ringing, buzzing, or clicking sound in ears in absence of auditory stimuli
Due to cochlear nerve degeneration, inflammation of middle or internal ears, side affects of aspirin
Tinnitus
Labyrinth disorder that affects cochlea and semicircular canals
Causes vertigo, nausea, and vomiting
Treatment: Anti-motion sickness drugs in mild cases or surgical removal of labyrinth in severe cases
Meinier’s Syndrome
