Term
| What is the 1st stage of perception? |
|
Definition
| Distal Stimulus--actual object or event, it is there even if you aren't present. |
|
|
Term
| What is the 2nd stage of perception |
|
Definition
| Proximal Stimulus--energy or substance that stimulates sensory system (you detect it) |
|
|
Term
| What is the 3rd stage of perception |
|
Definition
| Transduction- stimulus information/energy is transduced into neural signals. Different animals have different sensitivities to different senses |
|
|
Term
| What is the 4th stage of perception? |
|
Definition
| processing – neurons change and manipulate information. Like filling in a blind spot or emphasis of differences. |
|
|
Term
| What is the 5th stage of perception? |
|
Definition
| perception – experience of sensing |
|
|
Term
| What is the 6th stage of perception? |
|
Definition
| 6. recognition --identifying, categorizing perceptions |
|
|
Term
| What is the 7th stage of perception? |
|
Definition
| Action – action modifies distal and/or proximal stimulus, starting the cycle over again |
|
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Term
|
Definition
| Distal or Proximal stimulus |
|
|
Term
| What other factors can affect your Perception (think the diagram) ? |
|
Definition
1. when you focus your Attention enhances processing of that feature and reduces others as well as affecting perception recognition and action
2. Knowledge (prior knowledge/experience) can affect your processing, perception, recognition and action due to you knowing where things should be etc
3. Consciousness encompasses perception recognition and action |
|
|
Term
| What is the stimulus for vision? |
|
Definition
|
|
Term
| what spectrum is light part of? |
|
Definition
|
|
Term
|
Definition
|
|
Term
| Medium wavelength is what color? |
|
Definition
|
|
Term
| Long wavelength is what color? |
|
Definition
|
|
Term
| Does light have a color/Hue? |
|
Definition
| NO only a wavelength, the others is perception |
|
|
Term
|
Definition
| a particle (packet) of EM energy |
|
|
Term
|
Definition
|
|
Term
|
Definition
| when electrons in atoms jump b/w stable energy states (orbitals) |
|
|
Term
| what is the wave description of light? |
|
Definition
| As photons travel, they generate oscillating electric and magnetic fields |
|
|
Term
| what determines wavelength? |
|
Definition
|
|
Term
| 4. SO Why do you suppose our eyes evolved to be sensitive to the wavelength range 400-700 nm and not other ranges of EM radiation? |
|
Definition
1. Shorter or longer wavelengths tend to be absorbed or pass through. The visible range reflects most physical objects
1. The sun produces a lot of it
2. It interacts with surfaces of objects |
|
|
Term
| what is required of an object in order to see it? |
|
Definition
|
|
Term
| what determines the appearance of an object? |
|
Definition
| how light is reflected from the object |
|
|
Term
| how is color determined on an object? |
|
Definition
| Second. Reflected wavelengths determine the perceived color of the object, other wavelengths are being absorbed |
|
|
Term
| what is white light? black? |
|
Definition
White light is an equal mixture of all wavelengths
Black all colors are absorbed and only few are reflected |
|
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Term
|
Definition
| Fourth. Intensity - determined by number of photons reflected (roughly equal to brightness) |
|
|
Term
| what are the 3 components of a color? |
|
Definition
| HUE (what wavelength is reflected) BRIGHTNESS (light green/dark green how much light reflected ) AND SATURATION |
|
|
Term
| what would happen if all light was transmitted? |
|
Definition
|
|
Term
| what would happen if all light was absorbed? |
|
Definition
|
|
Term
| why don't you see a clear glass object on the dark side of the room? |
|
Definition
| b/c the clear glass is not reflecting any light |
|
|
Term
| what determines the perceived surface texture of an object? |
|
Definition
| 1. The spatial pattern of reflected light determines the perceived surface texture of the object |
|
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Term
| Define specular and Diffuse |
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Definition
| 2. Specular is Shiny and Diffuse is Rough in terms of the reflection on surface texture |
|
|
Term
| Is the incident angle always the same as the perceived angle? |
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Definition
| Yes, just diffuse objects have varying incident angles |
|
|
Term
| What kind of animals have lateral eye placement? |
|
Definition
|
|
Term
| What is an advantage of laterally placed eyes? |
|
Definition
| less blind spots, but also less binocular vision |
|
|
Term
| What kind of animals have frontal placed eyes? |
|
Definition
| 1. Like primates, cats and owls |
|
|
Term
| Characteristics of Frontal placement eye? |
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Definition
| 2. Large binocular areas and large Blind Spots |
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|
Term
| What kind of eye muscles do we have? |
|
Definition
1. We have two on top and bottom and two on the sides
2. The oblique muscle wrap around the top of the eye and help stabalize the eyes in the sockets |
|
|
Term
| What is vergent movement of the eyes? |
|
Definition
| Vergent- Eyes move in opposite directions to focus on objects at different distances (changing focus from objects at different distances) |
|
|
Term
|
Definition
Convergent- eyes move toward each other (close object)
Divergent-eyes move away from each other |
|
|
Term
| What is conjunctive movement |
|
Definition
| 2. conjunctive --eyes move in the same direction |
|
|
Term
| What is Pursuit movement? Saccadic? |
|
Definition
1. Pursuit- slow, smooth movement to maintain fixation on a movement object (requires a moving object)
2. Saccadic-fast, abrupt movement to change fixation |
|
|
Term
| What is the first layer of the eye? |
|
Definition
|
|
Term
| What is and what is the function of the sclera? |
|
Definition
1. Sclera - tough, white outer coating composed of densely packed fibers (primarily collagen)
1. Protect inner structures of eye
2. Maintain shape of eyeball
3. Keep out stray light
Reflects most light that hits it b/c it is white |
|
|
Term
| What is the cornea and what is the function? |
|
Definition
2. Cornea -transparent, dome-shaped surface at the front of the eye
Focuses light onto retina (2/3 of refractive power) 2/3--70% of refractive power |
|
|
Term
| Where does cornea get nutrients from? |
|
Definition
| No internal blood supply gets nutrients from the aqueous humor and gets oxygen from air and nourished from tears, but it has a lot of nerve endings |
|
|
Term
| Why is cornea transparent? |
|
Definition
|
|
Term
|
Definition
| when the cornea isn't spherical |
|
|
Term
| What is the second layer of the eye? |
|
Definition
|
|
Term
|
Definition
| - heavily pigmented layer running along the inside of the sclera |
|
|
Term
| Where does the choroid get its nutrient supply? |
|
Definition
| 1. Blood vessels feed retina and other eye structure |
|
|
Term
| what is purpose of Choroid? |
|
Definition
2. Absorbs scattered light, heavily pigmented
3. Other animals have the tapetum lucidum which assists in night vision (cats, possums etc) |
|
|
Term
|
Definition
| 2. Ciliary body-spongy tissue near front of eye, produces aqueous humor, filling the anterior chamber |
|
|
Term
| What does the ciliary body continually produce? |
|
Definition
|
|
Term
| What is purpose of the Ciliary BOdy? |
|
Definition
Maintains shape of cornea
Nourishes cornea and lens
Carries away waste products |
|
|
Term
|
Definition
| too much accumulation of Aqueous Humor and not enough exiting through the pores |
|
|
Term
| What else is in the 2nd layer? |
|
Definition
Anterior chamber/Aqueous humor)
Ciliary muscles |
|
|
Term
| What is the total components of the 2nd chamber? |
|
Definition
1.Choroid
2.Ciliary Body
3.Anterior Chamber/Aqueous Humor
4.Ciliary Muscles
5.Iris
6.Pupil
7.Lens
8.Ciliary Muscle
9.Vitreous Chamber/Humor |
|
|
Term
| What is the Stroma, and where is it? |
|
Definition
| It is in the Iris pigmented layer determines the color of eye (pigmented by melanin) |
|
|
Term
| Iris is an extension of what? |
|
Definition
|
|
Term
|
Definition
| Muscles controlling size of pupil |
|
|
Term
| What is the Circular Muscle and Radial Muscle? |
|
Definition
Circular muscle AKA sphincter when contracts, makes pupil smaller
Radial muscle AKA dialator, when contracts makes pupil larger |
|
|
Term
| How much more light enters the pupil when it is large as opposed to small? |
|
Definition
|
|
Term
| What is the function of the lens? How much refractive power is contained w/in lens? |
|
Definition
| capsule, epithelial layer, lens)-focuses image onto retina (1/3) of eyes's refractive power |
|
|
Term
|
Definition
1. Change shape to focus on objects at different distances (accomodation)
Fat near, flat far |
|
|
Term
| For near objects the lens is ? Far? |
|
Definition
|
|
Term
| The lens has 3 layers. what are they? |
|
Definition
| 3 layers Lens Epithelial layer and Capsule |
|
|
Term
| What does the Ciliary Muscle do in the lens? |
|
Definition
| Contracts or relaxes to change shape of lens (accomodation) |
|
|
Term
| How is the lens suspended? |
|
Definition
| 1. Lens is suspended by fibers (zonules of zinn) from ciliary body |
|
|
Term
| Far objects: Ciliary muscle, Zonules and lens |
|
Definition
Ciliary muscle relalxes
Zonules pulled tight
Lens pulled flat |
|
|
Term
| Near objects,Ciliary muscle, Zonules and lens |
|
Definition
Ciliary muscle contracts
Zonules go slack
Lens gets fat |
|
|
Term
| Near objects: Ciliary muscle, Zonules and lens |
|
Definition
Ciliary muscle contracts
Zonules go slack
Lens gets fat |
|
|
Term
| What is description and function of the Vitreous chamber/humor ? |
|
Definition
| Behind lens is the vitreous chamber-contains vitreous humor, a jelly-like substance that helps the eye maintain its shape. With age, it liquifies, floaters accumulate in it and it may separate from retina |
|
|
Term
| What is the 3rd layer of the eye consist of? |
|
Definition
| Retina, Macular/fovea, Pigment epithelium, optic disk |
|
|
Term
| What converts the sensory input into electrical cells? |
|
Definition
|
|
Term
| What direction do light and neural signals travel? |
|
Definition
|
|
Term
| image of fixated object falls here... |
|
Definition
|
|
Term
| Where do you have the highest concentration of photoreceptors ? Why? |
|
Definition
| Fovea and Third. Cell bodies of other neurons are displaced from fovea |
|
|
Term
| Are there blood vessels over the fovea? |
|
Definition
|
|
Term
| What is the Pigment Epithelium? What is part of? |
|
Definition
Contains building blocks of photopigments that contain melanin.
Part of Choroid |
|
|
Term
|
Definition
| 1. Hole, the blind spot, where blood vessels enter/leave the eye |
|
|
Term
| What are optical systems? |
|
Definition
| Systems that are able to form images |
|
|
Term
| What are 3 photosystems that occur in nature? |
|
Definition
| 1. Pinhole aperture 2. Fixed lens 3. variable lens |
|
|
Term
| Why does a pinhole aperature get a focused image at any distance? |
|
Definition
| only one ray of light gets through the pinhole from each location on the object. |
|
|
Term
| What direction is the image with a pinhole aperture? |
|
Definition
| Image is upside down and backwards |
|
|
Term
| In a pinhole aperture what does the size of the image depend on? |
|
Definition
| The size of the image depends on the distance of the object from the aperture (also true for lenses) |
|
|
Term
| When the pinhole is too large in a pinhole aperture, what happens? |
|
Definition
| you get a blurry image because light is hitting multiple spots on the retina |
|
|
Term
| What are the two types of lens systems? |
|
Definition
|
|
Term
| What are the two optical systems called? |
|
Definition
| 1. Pinhole 2. Lens System |
|
|
Term
| What is the difference between the Lens system and the Pinhole System? |
|
Definition
| Pinhole: Only lets a few light rays through to form a focuses image. Lens: Aperture (pupil) lets many rays through and the lens bends (refracts) the rays so they converge to form a focused image |
|
|
Term
| What happens to light when it travels into a new medium? |
|
Definition
| It slows down and changes direction. Exception: When the light hits perpendicularly to the medium, it will not change direction. |
|
|
Term
| The amount of refraction depends on what? |
|
Definition
| 1. Angle of incidence 2. The index of refraction |
|
|
Term
| What part of your eye has a similar index of refraction as water? |
|
Definition
|
|
Term
| What type of lens do you see more biologically? |
|
Definition
|
|
Term
| What does a convex lens do to light rays? |
|
Definition
| Converges to form a focused image |
|
|
Term
| Where the image comes into focus depends on what? |
|
Definition
| 1.Distance of the object from the lens 2. Curvature of the lens (fatter lens refract or bend light more) |
|
|
Term
| What does a concave lens do to light rays? |
|
Definition
|
|
Term
| What animals have a fixed lens (one that doesn't change shape)? |
|
Definition
|
|
Term
| For a fixed lens system: Near object causes image formation where and what does this cause? Mid-distance? Far object |
|
Definition
| Near object:Image formation behind retina and causes a blurry picture Mid distance: On retina, focused Far object: In front of retina, blurry |
|
|
Term
| What two parts of the eye have the ability to change in order to focus an image? |
|
Definition
|
|
Term
| Variable Lens System: For a near object the lens would be what thickness? Mid-object? Far object? |
|
Definition
| Near object: Thick Mid-Object: Middle thickness Far object: Thin |
|
|
Term
|
Definition
| compensating for the distance of objects |
|
|
Term
| What is the visual angle? |
|
Definition
| Measuring the size of a retinal image |
|
|
Term
| What is the width of your thumb at arms length in terms of visual angle? |
|
Definition
|
|
Term
| How much visual angle is about .3mm on the retina? |
|
Definition
|
|
Term
| The visual angle of an object is larger when... |
|
Definition
| it is closer to the eye (duh) |
|
|
Term
| What allows us to change the thickness of our lens? |
|
Definition
| By accommodating action of the ciliary muscle which changes the ability of the lens to refract light. |
|
|
Term
| What happens if the retina is fixed and the distance between the retina and the lens is fixed? |
|
Definition
| There is only one distance that an object can be at and form a focused image on the retina |
|
|
Term
| What is the visual angle? |
|
Definition
| How we measure the size of an image on the retina |
|
|
Term
| What do animals do in terms of focusing an image? |
|
Definition
| Animals will move lens forward and back to accommodate for distances (moving fixed lens) |
|
|
Term
| The visual angle is ____ when it is closer to the eye? |
|
Definition
|
|
Term
| 1 degree visual angle = ____ mm on the retina |
|
Definition
|
|
Term
| What are the four types of vision problems? |
|
Definition
1. Natural Imperfections / Optical defects in the eye that we don't usually worry about
2. Focusing Problems that we worry about
3. Retina Problems
4. Optic Nerve Problems |
|
|
Term
| What is chromatic aberration? |
|
Definition
| When different wavelengths come into focus at different distances from the lens. The lens is refracting different wavelengths differently which creates a blur. Note: Short wavelengths come into focus in front of retina. Med on retina. Long behind retina. |
|
|
Term
| What is Spherical Aberration |
|
Definition
| Refractive power of lens is different at edges that in the middle. Causes blurriness. You would be seeing red on top and blue on the bottom (colors go with example from class) |
|
|
Term
| What are the 5 Natural Imperfections / Optical Defects? |
|
Definition
| 1. Chromatic Aberration 2. Spherical Aberration 3. Random Variations in cornea or lens 4. Diffraction 5. Other light scatter |
|
|
Term
| What is random variations in cornea or lens? |
|
Definition
| Cornea or lens are not perfect and this can be anywhere from normal to severe. |
|
|
Term
|
Definition
| Photons hit edge of iris/pupil and scatter into eye (a little image degradation) |
|
|
Term
| What does other light scatter refer to? |
|
Definition
| Photons reflect off of other things in the eye |
|
|
Term
| What are the steps for Cataract surgery? |
|
Definition
| . Remove lens leaving capsule intact 2. Small slit in eyeball and use ultra sound to break up lens and suck it out of capsule. 3. Insert a plastic lens in the capsule |
|
|
Term
| What are the 5 focusing problems that we worry about? |
|
Definition
| 1. Astigmatism 2. Cataract 3. Myopia 4. Hyperopia 5. Presbyopia |
|
|
Term
|
Definition
| Cornea is not spherical. Looks like a rugby ball |
|
|
Term
|
Definition
| Clouding of the lens. The lens is opaque. |
|
|
Term
| What delays the onset of Cataracts? |
|
Definition
|
|
Term
| What is actually happening within the eye that causes Cataracts? |
|
Definition
| Proteins in the lens oxidate and become damage. This occurs over the course of your life. Smoking and UV increase risks. |
|
|
Term
| What does it mean in terms of the lens have myopia? What is this also called? |
|
Definition
| Nearsighted :Lens cannot get thin enough to focus on far objects so the image comes into focus in fron of retina. |
|
|
Term
| What type of corrective lens are used for nearsighted vision? |
|
Definition
|
|
Term
| What can't you see if you're myopic? |
|
Definition
|
|
Term
| What are the two ways to be nearsighted? And what does each one mean? |
|
Definition
| 1. Axial: Eye too long 2. Refractive: Cornea and lens bend light too much Note: You have different curvature on the horizontal plane then the vertical plane |
|
|
Term
| What does it mean in terms of the lens when you have hyperopia? What is this also called? |
|
Definition
| Farsighted:Lens cannot get far enough to focus on near objects, so image comes into focus behind retina. Lens cannot get fat enough to focus on near object |
|
|
Term
| What type of corrective lens is used for farsighted people? |
|
Definition
|
|
Term
| What are the two ways to be farsighted? And what does each one mean? |
|
Definition
| 1. Axial: eye too short 2. Refractive: cornea and lens bend light too little (too flat) |
|
|
Term
| What does it mean to have presbyopia? |
|
Definition
| It is the hardening of the lens. So you cannot focus on near objects |
|
|
Term
| Why does presbyopia occur? |
|
Definition
| It happens because of the accumulation of lens fibers |
|
|
Term
| When does lens fiber accumulation occur? What does this mean for the flexibility of the eye? |
|
Definition
| It starts when you are born. The lens continually gets less and less flexible. |
|
|
Term
| Define nearpoint? What happens to nearpoint as you age? |
|
Definition
| Nearpoint: closet an object can be to you and still be in focus. The older you get the farther from you the object must be. |
|
|
Term
| In the retina, what two types of vision systems are there? |
|
Definition
|
|
Term
| What is Scotopic and Photopic? |
|
Definition
1. Photopic System-Cone driven system
2. Scotopic System-rod driven system |
|
|
Term
| Where is the outer segment in the photorecptors? |
|
Definition
| Partially embedded in the retinal epithelium |
|
|
Term
| Which photoreceptor has disks inside the cell membrane and which are attached to cell membrane? |
|
Definition
Rod--inside membrane
Cone--attached to membrane |
|
|
Term
| What are the two photopigments in the photoreceptors? What is special in Rods? |
|
Definition
Opsin and Retinal
Rhodopsin in Rods |
|
|
Term
| What affects wavelength sensivity of retinal? |
|
Definition
|
|
Term
| What controls wavelength sensitivity>? |
|
Definition
|
|
Term
| How often are the disks (photopigment complexes) regenerated ? |
|
Definition
|
|
Term
| Where are the regenerated disks formed and what happens to the old ones? |
|
Definition
| Produced at bottom released at top into pigment epithelium |
|
|
Term
| Describe the process of transduction. |
|
Definition
1. Photon hits retinal
2. Retinal isomerizes (changes shape [11-cis Retianl -->all-trans retinal]) and photopigment (opsin or Rhodopsin) changes conformation-->
3. Cascade of chemical events (and retinal separates from opsin) -->
4. Neural Signal
PRCN |
|
|
Term
| How long does regeneration take for cones?Rods? |
|
Definition
Cones: 6mins
Rods: 30mins |
|
|
Term
| What photoreceptor is inactive during the day? |
|
Definition
|
|
Term
| Describe the pigment regeneration of the photoreceptors... |
|
Definition
1. Light hits 11-cis retinal
2.11-cis retinal isomerizes to All-Trans retinal
3. All-trans retinal separates from opsin (bleaching)
4.All-trans retinal transported to pigment epithelium
5. All-trans retinal is reduced to Vitamin a
6. Vitamin A is metabolized to 11-cis retinal
7. 11-cis retinal transported to photoreceptor outer segment |
|
|
Term
| What photoreceptor is unable to separate wavelength and intensity information? |
|
Definition
|
|
Term
| Rods signal _____ NOT ______ |
|
Definition
| INTENSITY (BRIGHTNESS) NOT WAVELENGTH (COLOR) |
|
|
Term
| 100 photons at at 500nm (green) wavelength is also just as intense as what other wavelength? What does this tell us? |
|
Definition
200 photons at 450nm (blue)
Rods can only respond to intensity so colors just have different intensity based on the nature of the color (IE green photons are twice as strong as blue photons) |
|
|
Term
| How many photopigments are there in rods? |
|
Definition
|
|
Term
| What are the 4 types of retinal problems? |
|
Definition
1. Retinitis pigmentosa
2. detached retina
3. Age-related macular degeneration
4. diabetic retinopathy |
|
|
Term
| what is retinitis pigmentosa ? |
|
Definition
| degeneration of retinal photoreceptors |
|
|
Term
| What happens to vision in adolescence? AKA |
|
Definition
| vision begins to deteriorate ;retinitis pigmentosa |
|
|
Term
| What photoreceptor goes first? Causing what? |
|
Definition
| 2. Rods go first, causing tunnel vision and night blindness |
|
|
Term
| How does one get Retinitis pigmentosa? |
|
Definition
| nearly all cases are inherited |
|
|
Term
| Essentially what happens in Retinitis Pigmentosa? |
|
Definition
| Loss of peripheral vision |
|
|
Term
|
Definition
| Retina detaches from wall of eye |
|
|
Term
| Why is Detached retina bad? |
|
Definition
| It disrupts the image and the retina dies |
|
|
Term
| What are some treatments for detached retina? |
|
Definition
| inject gas bubble to push retina back into eye or scleral buckle |
|
|
Term
| What is Age-Related Macular Degeneration? |
|
Definition
| loss of central vision due to degeneration of macula |
|
|
Term
| What are the 2 types of Age-Related Macular Degeneration? Describe in Detail. |
|
Definition
Dry and Wet
One. In "dry" type, pigment epithelium and cones atrophy and die
Two. In "wet" type, choroidal blood vessels overgrow and leak, detaching the retina |
|
|
Term
| What kind of vision loss is associated with Age-Related Macular Degeneration? |
|
Definition
|
|
Term
| What vitamins help delay the onset of Age-Related Macular Degeneration? |
|
Definition
|
|
Term
| What is the leading cause of blindness for ppl over the age of 65 in the US? |
|
Definition
| Age -Related Macular Degeneration |
|
|
Term
| What is Diabetic Retinopathy? |
|
Definition
| Condition that can cause aneurisms or vessel blockage in the retina. It can Three. Also can cause neovascularization - overgroth of capillaries causes leakage, swelling, scarring, and blindness |
|
|
Term
| Who is most at risk for developing Diabetic Retinopathy? |
|
Definition
| Insulin dependent diabetics; 40% show some degree of DR |
|
|
Term
| What are some Optic Nerve Problems? |
|
Definition
| Multiple Sclerosis and Glaucoma |
|
|
Term
|
Definition
| Demyelinating disease. the optic nerve (eye-brain pathway) is myelinated |
|
|
Term
| What happens to the optic nerve in MS? How does this disrupt vision? |
|
Definition
1. Optic nerve can become inflamed, disrupting vision
2. One of the first symptoms is blurry vision |
|
|
Term
|
Definition
| Aqueous Humor is trapped in eye and Intraocular pressure builds damaging optic nerve at optic disk |
|
|
Term
| What cells are damaged by the pressure in Glaucoma? |
|
Definition
|
|
Term
| How many cones do we have in our photopic vision? Rods? |
|
Definition
| Cones=5-8million/eye Rods=120million/eye |
|
|
Term
| What degree is the rod free area in the fovea? |
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Definition
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|
Term
| How many degrees is the distribution of rods? |
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Definition
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Term
| Are there any rods in the fovea? |
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Definition
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Term
| What is the spectral sensivity for system peak for color? short, med, long? |
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Definition
560
short=420, med=530, long=560 |
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Term
| What is spectral sensitivty for Scotopic vision (system)? |
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Definition
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Term
Photopic: intesnsity sensitivity
scotopic? |
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Definition
Photopic: low in dim light
scotopic: high in dim light |
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Term
| What is the acuity of photopic vs scotopic vision? |
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Definition
photopic: high (lack of spatial summation)
scotopic: low (low resolution, high spatial summation) |
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Term
| Light/dark adaptation photopic vs scotopic |
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Definition
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Term
| How is hue conveyed to the brain? |
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Definition
| pattern of response and intensity by amount of response per cone. |
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Term
| at 500 nm do short cones get stimulated? what color is short cones? |
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Definition
| blue do not get stimulated at 500nm, they peak at around 450 |
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Term
| Is Rhodopsin or opsin better at absorbing wavelengthS? |
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Definition
|
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Term
| What is threshold intensity? |
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Definition
| lowest detectable intensity that can be reliably seen |
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Term
| High sensitivty = ____ threshold |
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Definition
|
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Term
| Low sensitivity = ____ threshold |
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Definition
|
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Term
| What is spatial summation? |
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Definition
| scotpic system has higher sensitivity to low levels of illumination |
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Term
| Spatial summation refers to what? |
|
Definition
| how many photoreceptors are connected to an individual ganglion cell |
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|
Term
| why does photopic system have greater acuity? |
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Definition
| only one ganglion cell per photoreceptor makes 2 spots of light much easier to distinguish. 2 spots=2 cells firing in different locations |
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Term
| why do infants have such poor vision? |
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Definition
| inner segments in infants have a very large diameter compared to the photpigment so photons can escape without triggering the firing of a cell |
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Term
| Is there anywhere in the retina where you can only activate cones? |
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Definition
|
|
Term
| Is there anywhere on the retina where you can stimulate just rods? |
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Definition
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Term
| As visual activity shifts from cones to rods during dark adaptation we become less sensitive to ____ ____ and more sensitive to ___ ____ |
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Definition
| Less sensitive to long wavelengths and more to short |
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Term
| What is purkinje shift? give an example. |
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Definition
| Shift from cone vision to rod vision that causes an enhanced perception of short wavelengths during dark adaptation. An example of this shift is that green foliages stands out more near dusk |
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