Term
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Definition
| the receptors for light; the rods & cones of the retina |
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Term
| The photoreceptors transform light energy to graded changes of the membrane potential with ensuing release of _____ |
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Definition
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Term
| From the photoreceptors, the signals pass to _____ cells & from these to _____ cells |
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Definition
| bipolar; retinal ganglion |
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Term
| Several kinds of _____ enable considerable information processing in the retina |
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Definition
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Term
| What is the difference between rods & cones? |
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Definition
rods: responsible for vision in dim light
cones: require daylight & are necessary for perception of visual details & colors |
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Term
| The visual pathways start with the retinal ganglion cells sending their axons to the _____ of the thalamus |
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Definition
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Term
| The ganglion cell axons leave the eye in the _____ nerve & pass through the optic chiasm, where the temporal half pass through uncrossed |
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Definition
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Term
| What tract leads from the optic chiasm to the lateral geniculate body? |
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Definition
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Term
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Definition
| formed from the axons from neurons in the lateral geniculate; leads to end in the primary visual cortex (the striate area) in the occipital lobe of the same side |
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Term
| Do visual pathways show a precise, retinotopical organization at all levels? |
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Definition
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Term
| Where does further processing take place after the area striata performs the first analysis of visual information? |
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Definition
| extrastriate visual areas in the occipital, temporal, & parietal lobes |
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Term
| Why is visual processing largely segregated? |
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Definition
| so that different areas deal with color & motion, etc. |
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Term
| 2 examples of visual reflex effects |
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Definition
1. ensuring fixation of our gaze on the object we want to examine & follows it if it moves
2. ensuring that the visual images formed at the retina are always in focus |
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Term
| What is the outer wall of the eyeball? |
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Definition
| dense connective tissue that is covered on the inside by the light-sensitive retina |
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Term
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Definition
| a vascular layer between the outer wall of the eyeball & the retina; highly pigmented to ensure that light enters the eye only through the pupil & prevent reflection of light |
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Term
| What does the diameter of the pupil control? |
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Definition
| the amount of light allowed into the eye |
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Term
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Definition
| vary the curvature of the lens; allows retinal image to be always sharply focused |
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Term
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Definition
| attach to the eyeballs & can move them to coordinate their positions so that visual images hit corresponding points of the two retinas |
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Term
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Definition
1. temporal parts (lateral parts, toward the temple)
2. nasal parts |
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Term
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Definition
| the lateral 30 degrees of the visual field that is viewed by one eye only; exists because the nose prevents light from reaching the anterior part of the temporal retina |
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Term
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Definition
| the visual field viewed by both eyes |
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Term
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Definition
| does a systemic examination covering all parts of the visual field for each eye |
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Term
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Definition
| thin fibers that attach the lens to the ciliary body |
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Term
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Definition
| an eye that is normal; the length of the eyeball is accurately adjusted to the refraction of the cornea & the lens in the relaxed state |
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Term
| What kind of glasses correct myopia? |
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Definition
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Term
| What kind of glasses correct hypermetropia? |
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Definition
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Term
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Definition
| adjustment of the lens for near sight |
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Term
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Definition
| the closest distance from the eye at which we can see an object sharply |
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Term
| What kind of glasses correct presbyopia? |
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Definition
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Term
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Definition
| the outer part of the retina that adjoins the choroid; consists of one layer of cuboid cells with large amounts of pigmented granules in their cytoplasm |
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Term
| 3 types of neurons/cells in the retina |
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Definition
1. interneurons
2. amacrine cells
3. horizontal cells |
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Term
| What type of cells in the retina are responsible for lateral inhibition? |
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Definition
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Term
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Definition
| the light-sensitive parts of the photoreceptors; lie externally, toward the pigmented epithelium |
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Term
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Definition
| the nuclei of the photoreceptors |
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Term
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Definition
| the nuclei of the bipolar cells |
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Term
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Definition
| the innermost layer of nuclei that belongs to the ganglion cells |
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Term
| 2 types of layers that lie between the nuclear layers & contain the processes of the neurons & their synapses |
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Definition
1. outer synaptic layer
2. inner synaptic layer |
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Term
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Definition
| a special kind of glial cell that extends through the retina from the pigmented epithelium to the vitreous body |
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Term
| Where is rhodopsin created? |
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Definition
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Term
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Definition
1. opsin (a protein part)
2. retinal (an aldehyde of vitamin A) |
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Term
| The transduction mechanism of the rods involves activation of _____ |
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Definition
| G proteins (structurally, the photopigments resemble closely other G protein-coupled receptors) |
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Term
| What is the difference between scotopic vision & photopic vision? |
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Definition
scotopic: comes from the rods; vision when the light is dim
photopic: comes from the cones; vision in good light |
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Term
| Can rods help us discriminate between light of different wavelengths (a prerequisite for color vision)? |
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Definition
| no! the distribution of light sensitivity for different wavelengths of light is the same for all the rods |
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Term
| 3 colors for which different kinds of cones respond best to (certain wavelengths) |
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Definition
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Term
| How do the neurons receiving signals from the different kinds of cones extract information about the distribution of wavelengths in the light falling on the retina? |
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Definition
| by comparing the degree of activation of the different kinds of cones |
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Term
| Together, what are the three kinds of cones responsible for? |
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Definition
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Term
| Is there a high or low degree of convergence for rods? |
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Definition
| high (many rods connect to each bipolar cell) |
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Term
| Do cones or rods provide information with a higher spatial resolution? |
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Definition
| cones (two points must be farther apart to be perceived as two when the rods are responsible for transmitting the information than when the cones are responsible due to the difference in convergence) |
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Term
| 2 things cones are responsible for |
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Definition
1. color vision
2. our ability to perceive visual details (precise perception of patterns & form) |
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Term
| Are photoreceptors depolarized or hyperpolarized in the dark? |
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Definition
| depolarized (with a membrane potential around -30 mV) |
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Term
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Definition
1. depolarized by light
2. hyperpolarized by light |
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Term
| How many parallel signal pathways come from the cones? |
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Definition
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Term
| Are on-center or off-center ganglion cells activated by light hitting the central zone of the receptive field? |
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Definition
| on-center (off-center are inhibited) |
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Term
What are contours especially important for?
*the visual system is particularly suited to detect contours* |
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Definition
|
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Term
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Definition
| a small region of the retina in the back of the eye; visual axes have to be oriented so that light from the object falls on it |
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Term
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Definition
| the distance two points in the visual field have to be apart to be perceived as two & not one |
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Term
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Definition
| a small depression in the center of the macula |
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Term
| Is the density of photoreceptors higher or lower in the fovea than in the periphery? |
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Definition
| higher (contributes to the higher visual acuity in the central parts of the retina especially the fovea) |
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Term
| Are the dendrites of ganglion cells longer centrally or peripherally? |
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Definition
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Term
| 2 main kinds of retinal ganglion cell (together they constitute about 90% of all cells) |
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Definition
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Term
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Definition
| where all ganglion cell axons pass through the wall of the eyeball after running toward the posterior pole of the eye |
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Term
| The optic radiation curves anteriorly & laterally to the posterior horn of the lateral ventricle & ends in the _____ (which is situated around the calcarine sulcus) |
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Definition
| primary visual cortical area |
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Term
| Which of Brodmann's areas is associated with the primary visual area & also known as the striate area? |
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Definition
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Term
| 2 main places in the mesencephalon where optic nerve fibers terminate |
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Definition
1. superior colliculus
2. pretectal nuclei |
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Term
| What do fibers of the optic nerve that pass to the hypothalamus do? |
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Definition
| contribute to regulation of circadian rhythms |
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Term
| What is the difference between the magnocellular layers & the parvocellular layers of the lateral geniculate body? |
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Definition
magno: the two ventral-most laminas composed of large cells
parvo: the dorsal four laminas composed of small cells |
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Term
| Is retinotopic localization fine-grained? |
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Definition
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Term
| Are the thalamocortical connections from the lateral geniculate body to the striate area organized with a precise retinotopic arrangement? |
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Definition
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Term
| Why may disease processes involving the visual cortex at times elicit sensations of light? |
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Definition
| the neurons are abnormally irritated |
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Term
| What does it mean that epileptic seizures originating in the visual cortex often start with a "visual aura"? |
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Definition
| the muscular convulsions are preceded by bizarre patterns of light in the visual field opposite the diseased hemisphere |
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Term
| direction-selective cells |
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Definition
| detect not only the orientation of a contour but also in which direction it is moving |
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Term
| What does it mean that many binocular cells are sensitive to "disparity" of the images? |
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Definition
| they require that the images from the two eyes are slightly different |
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Term
| 2 things that binocular disparity is important for |
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Definition
1. depth
2. stereoscopic vision |
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Term
| 3 properties associated with modular organization |
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Definition
1. orientation selectivity
2. wavelength selectivity
3. ocular dominance |
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Term
| 4 things neurons in the striate area are the basis for cortical analysis of |
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Definition
1. form
2. depth
3. movement
4. color |
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Term
| What is the difference between the ventral stream of information passing downward from the occipital lobe to the temporal lobe & the dorsal stream that passes upward to the parietal lobe? |
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Definition
ventral: object identification
dorsal: spatial features & movement |
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Term
| What causes color opponency? |
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Definition
| convergence on one ganglion cell of signals from cones with different wavelength sensitivities |
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Term
| Is there one final site in which all aspects of visual information are brought together? |
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Definition
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Term
| In the prefrontal cortex, is visual information about "what" & "where" treated separately? |
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Definition
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Term
| In the first 2 to 3 years of life, what can result from lack of meaningful use of the eye? |
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Definition
| permanently reduced visual acuity |
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