QUIZ 4 VISION STUDY GUIDE 1 Know characteristics of light that it is measured according to wavelength that opsins chromophores absorb packets of light called photons A light can be refracted bent reflected visible or absorbed when we see we are looking at a type of electromagnetic radiation and we can only see a portion of it visible light from 400 nm to 700 nm lower wavelengths have bluish hues higher wavelengths have reddish hues 2 Know the parts of the eye and their function a Cornea protective layer of the eyeball when scratched it engages in tear production so as to prevent further damage to tissue b Iris Pupil iris is the colored portion pupil is the black hole in the middle together they help regulate the amount of light intake in the dark the pupil enlarges to let in more light c Vitreous Humor gel that fills chamber behind the lens for further refraction of light d Aqueous Humor fluid between the cornea and the lens e Lens refracts and focuses light on the retina for accurate representation if it isn t functional glasses are needed f Retina at the back of the eyeball contains photoreceptors 3 Know the components of a photoreceptor Know how different opsins are distributed and how they determine what each photoreceptor detects Each photoreceptor contains an outer segment inner segment and synaptic terminal The inner segment produces pigments and contains neurotransmitters proteins and other cellular machinery the outer segment stores the pigments Within the pigments there are chromophores pigment molecules that capture photons and opsins proteins that detect a certain wavelength of light chromophores are within the opsin proteins Rhodopsin is used by rods cones have one of three opsins that detects a certain wavelength s m l discussed in the following question 4 What are rods cones and in what type of environmental conditions are they most effective Know the three types of cones and the wavelengths colors they respond to along with how they are distributed across the retina Rods are most active in scotopic low light conditions we use them when our environment is mostly dim or dark Rods allow one to depict shape of objects and contrast mostly in the periphery of the retina Cones respond to photopic daylight conditions they detect color and are responsible for color vision There are three types determined by their opsins that detect different wavelengths of color s cones contain opsins that respond to short wavelengths blue m cones contain opsins that respond to middle wavelengths green l cones respond to long wavelengths red Cones are mostly focused in the fovea for acuity few rods in the fovea L and m cones are distributed more in the fovea s cones distributed more in the periphery 5 Be able to differentiate between the inner and outer segments of photoreceptors in both appearance and function Outer segments look like a comb they store the visual pigments and participate in transduction inner segments are below the outer segments and they look more like chambers Inner segments produce the pigments contain NTs proteins other cellular machinery When looking at a diagram of the opsin it is an ovular protein shape 6 Be able to label a graph of the cells in the retina Change Blindness Powerpoint Slide 4 Starts with photoreceptors at the back of the eyeball Horizontal cells are next acting as a bridge to the bipolar cells in middle of section area Amacrine cells follow acting as a bridge to the ganglion cell in the next Amacrine and horizontal cells are not along the main path but off to the side horizontal before bipolar amacrine before ganglion 7 Know the neuroanatomical pathways that carry visual information into and throughout the brain including regions and when information crosses to the other hemisphere The optic nerve picking up from the optic disc to the optic chiasm where one half of the neurons cross to the contralateral side then to the optic tract optic nerve after the chiasm The optic tract then projects to two different areas the superior colliculus and lateral geniculate nucleus of the thalamus The superior colliculus processes movement creates a map of visual space and is responsible for blindsight The LGN then prjects visual information to the striate cortex V1 8 What is the blind spot optic disc and what is a unique feature of this area i e what causes the blindness lack of photoreceptors Axons of ganglion cells join to form the optic nerve or optic disc in the fovea it is where the optic nerve leaves the eye it is a result of retina organization This is called camera eye where the optic disc leaves medial towards the nose to the fovea causing a blind spot in the lateral vision field to the right or left of center of vision 9 Read and be able to answer questions regarding the flicker technique Know how we typically detect visual field changes and why the flicker technique results in change blindness Normally change in an image can be detected through local motion signals even if attention is not paid to the scene Superior Colliculus The disturbance or flicker overloads this ability of detection With the Superior Colliculus disrupted the brain has to use dedicated attention and the visual cortex to search the scene item by item until the change is found However changes to important items in the scene can be detected more readily because your brain will look at those important items first 10 What are the monocular and binocular cues involved in depth perception Describe them Monocular Texture it is harder to differentiate texture of farther objects Linear Perspective the property of parallel lines converging at infinity allows us to gauge relative distance of objects landscape features based on how close they seem to each other Relative Size the larger of two objects will appear closer Occlusion Interposition two objects overlap and the front most object is seen as closer so if object A covers part of object B object A is closer think cityscapes Binocular Convergence difference in images seen in each eye due to the angle the object is viewed at the convergence angle will be smaller for farther objects and larger for closer objects Retinal Disparity each eye sees a slightly different image and the brain combines information from those two images to create overall perception of the object each eye sees something different Parallax apparent displacement or difference of orientation of an object viewed along two different lines of sight and is measured by the
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