Will consist of multiple choice fill in the blank matching and short answer questions 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 Know this 2 Know the parts of the eye and their function Cornea protective layer of eyeball When scratched tear production is used to prevent further scratching Aqueous Humor Fluid between cornea lens Iris Pupil together help regulate the amount of light Iris colored portion Pupil black portion in its center In dark enlarges to let more light in Lens retracts and focuses light on the retina for accurate representation If not functional need glasses Vitreous humor gel that fills chamber for further retraction Retina 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 Components of a photoreceptor Located in the retina Detect visual information Two types Rods cones Rods detect amount of light shapes and contrasts Cones detect color Each are composed of an inner and outer segment and a synaptic terminal connected to the next cell layer o Inner segment produces visual pigments neurotransmitters proteins and other cellular machinery o Outer segment stores visual pigments transduction The visual pigment molecules consist of Opsin Protein that detects the wavelength of light Different opsins for responding to different stimuli Used by rods rhodopsin Each cone has 1 3 other opsins that detect Long wavelengths red Medium wavelengths green Short wavelengths blue Chromophores pigment molecule captures photons of light 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 Most active is scotopic low light conditions We use our rods mainly when environment is dim or dark Nocturnal animals rely heavily on rods Shape contrast of objects Cones Respond mainly to photopic daylight conditions Detect color and are responsible for color vision 3 subtypes of cones 3 different opsins o Long wavelengths red o Medium wavelengths green o Short wavelengths blue Trichromacy the condition of possessing three independent channels for conveying color information derived from the 3 different cone types Rods and cones are distributed differently throughout the retina In the periphery of the retina rods are highly concentrated few cones When the images fall in the periphery of the retina from out peripheral vision visual acuity is not very good In the center of the retina fovea Blind spot neither rods nor cones Contains no photoreceptors optic nerve leaves the eye to transmit visual information to the brain 5 Be able to differentiate between the inner and outer segments of photoreceptors in both anatomy and function Inner segment produces visual pigments neurotransmitters proteins and other cellular machinery Contains mitochondria ribosomes and membranes where opsin molecules are assembled and passed to be part of the outer segment discs Outer segment stores visual pigments transduce signals Contain receptors for light Consists of opsins and chromophores o Chromophore changes shape stores photon of light o Opsins are G Protein coupled receptors absorbs photon of light Filled with stacks of membranes 6 Be able to label a graph of the cells in the retina Change Blindness PowerPoint Slide 4 Photoreceptors connect to horizontal cells and bipolar cells Bipolar cells connect to amacrine cells and ganglion cells Ganglion cell axons from the optic nerve to the brain fire action potentials 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 axons of the ganglion cells converge and leave via the optic nerve the fibers in the optic nerve cross to the contralateral side of the brain at the optic chiasm From the optic chiasm visual information is carried via the optic tract First synapse the optic tract makes is in the lateral geniculate nucleus of the thalamus acts as a relay station to project visual information to the occipital lob aka striate cortex primary visual cortex and area 17 and V1 The striate cortex is made of 6 layers Each layer receives a different type of information Cells in the striate cortex respond to several things lines or edges angles movement faces In other words Optic nerve begins at optic disc Optic chiasm of the neurons cross to contralateral side Optic tract projects to two areas 1 Superior colliculus processes movement responsible for blind sight 2 Lateral geniculate nucleus LGN of thalamus relays info bound for cortex 8 What is the blind spot optic disc and what is a unique feature of this area i e what causes the blindness Optic disc blind spot Axons of ganglion cells join to form the optic nerve Called optic disc in retina Optic nerve leaves medial to fovea Blind spot appears lateral to the center of vision Blind spot Contains no photoreceptors Where the optic nerve leaves eye A result of retina organization 9 Read and be able to answer questions regarding the flicker technique Know how we typically detect change and why the flicker technique results in change blindness Two images of scenes alternate repeatedly Brief 80 millisecond blank screen after each image The image appears as though it is flickering Large changes could be made to the scene without the observer reliably noticing them Change blindness inability to detect changes to a visual object or a scent Implications very large changes can be made in a picture without observers noticing them Cause change blindness A change is detected by local motion signals it is easy to notice movement thanks to the superior colliculus The disturbance flicker overloads bypasses this means of change detection The brain is forced to search the scene item by item until the change is detected Changes to objects that are more important to the picture will be noticed more quickly than changes to objects less important to the scene you re more likely to scan the important objects first 10 What are the monocular and binocular cues involved in depth perception Describe them Monocular cues the ability to perceive the distance of an object from a single eye Relative size if two objects are roughly
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