Vision Study Guide PDF

1. How does vision work? perception begins when a stimulus from the environment stimulates one of our sense organs. Perception is the mental representation of that original stimulus. When light enters, get adjusted by the. Bipolar cells - pass the visual info Ganglia cells - integrate those signals...

1. How does vision work? perception begins when a stimulus from the environment stimulates one of our sense organs. Perception is the mental representation of that original stimulus. When light enters, get adjusted by the. Bipolar cells - pass the visual info Ganglia cells - integrate those signals in Horizontal cells - combine diff signals from photoreceptors cells Photoreceptors consist of rods and cones; these are specialized cells sensitive to light. ​Rods are more sensitive to low light and help in night vision, while cones detect color and are essential for detailed vision. They convert light into electrical signals through phototransduction. Rods and cones are located on our retina RODS CONES Long, cylindrical shape Color perception Many photopigments Suited for day time vision 120 million rods 6 million Less sensitive to light - suited for night Concentrated in the centre of retina time Fovea : sharpest vision, highest visual Equally distributed accuracy/spatial resolution Receptive fields: capture light, layed in the most outer layer of the retina. ON AND OFF refers to the receptive field not the bipolar cell Off bipolar cells - depolarize (respond to less light) On bipolar cells - hyperpolarize (respond to more light) Horizontal cell release GABA which inhibits the photoreceptors 2. How do optical illusions work? Grid illusion - lateral inhibition: neural process retina. Something that the brain does to help see outlines better. When you look at intersections in these grid illusions, the surrounding "on-center, off-surround" retinal cells receive input from both the intersecting white areas and the dark lines around them. Because cells at intersections receive more total light from nearby white spaces, their surrounding cells inhibit them more strongly, creating a faint shadow or illusionary dark spot that fades when directly focused on. Rods and cones can get tired - they can get ‘overstimulated’ 3. What can interfere with our visual processing? Colour blindness - genetic condition, usually a gene that produces an abnormality in the photoreceptor system. Related to how certain photoreceptors detect wavelengths. Dichromats: are people with only two photopigments. Disorders of colour perception can also occur from disturbance of the CNS called achromatopsia. Usually caused by rather big lesions. Akinetopsia describes the loss of motor perception Blind spot = optic disc 4. How does light turn into neurotransmission in the eye (focus on the retina, not the brain)? Isomerization is the process of changing the shape of the photopigments Bipolar cells become ON or OFF because they develop either mGluR6 receptors (making them ON cells) or AMPA/kainate receptors (making them OFF cells)