Chapter 6: Vision Flashcards
exam 2 material
what do wavelength and amplitude represent in light?
wavelength determines the color of light, amplitude determines brightness/intensity of the light
what protects the eye?
eye is located in bony orbit of the skull and cushioned by fat, eyelids, blinking, and tears also protect it
what is the anatomy of the retina?
retina contains visual interneurons and photoreceptors, axons forming the optic nerve exit the eye at the optic disk forming a blindspot, macula is where images in our central vision are projected, fovea is in the center of the macula and is responsible for detailed vision
what are the layers of the retina?
ganglion cell layer: inner-most layer, forms the optic nerve
inner plexiform layer: where ganglion cells form connections with amacrine and bipolar cells
inner nuclear layer: amacrine and bipolar cells
outer plexiform layer: where bipolar cells form connections with horizontal cells and photoreceptors
outer nuclear area: contains the cell bodies of the photoreceptors
what are the two types of photoreceptors?
rods: scotopic vision, high density in the peripheral retina, see dim light, contains rhodopsin photopigment
cones: photopic vision, high density in the fovea, best visual acuity, color vision, have blue/short, green/middle, and red/long wavelength cones
how does transduction occur in rods?
in darkness rods are depolarized at rest and sodium channels are open due to cGMP, increased glutamate
light stimulus splits rhodopsin and enzymes break down cGMP, decreased glutamate
photoreceptor becomes hyperpolarized with return to darkness and rhodopsin rejoins
what do horizontal cells in the eye do?
form connections with photoreceptors and bipolar cells
what do bipolar cells in the eye do?
have antagonistic center-surround organization: light falling in the center of the receptive field has the opposite effect on the cells activity from light falling in the surround, either light activates cells in the center or around the outer rim, and vice versa, which allows bipolar cells to identify boundaries of an object
what do amacrine cells in the eye do?
form connections between bipolar, ganglion, and other amacrine cells, process movement
what do ganglion cells in the eye do?
receive input from bipolar and amacrine cells, receptive fields replicate the information passed to them by the bipolar cells, antagonistic center-surround organization
what do the optic nerves and its connections do?
optic nerves: ganglion cell axons exit each eye through the optic disk, forming an optic nerve leaving each eye, optic nerves cross at the optic chiasm
superior colliculus: guides movements of the eyes and head
toward a newly detected object
lateral geniculate nucleus (LGN): receives 90% of optic tract axons and keeps input from each eye separate
what is the primary visual cortex?
the striate cortex located in the occipital lobe, the position of an object is correlated with activity in the visual cortex
what is the organization of the striate cortex?
neurons in the visual cortex are organized into cortical columns, cortical modules (groups of columns) connect information processed by different types of cortical columns, ocular dominance columns respond to input from only one eye and orientation columns respond to lines of the same angle, adjacent columns respond to angles shifted about 10 degrees, cytochrome oxidase blobs process information regarding color
ventral vs dorsal stream
the dorsal stream is the where, plays an important role in processing motion the ventral stream is the what, important for object recognition
what cues help us identify depth?
monocular cues: perspective, texture, and shading, comparison of size of familiar objects
binocular cues: the difference between the images projected onto the retinas of both eyes results in retinal disparity, which increases as an object moves closer, binocular cells in the cortex respond to retinal disparity
