Chapter 7 - Vision

• retina


  the receptive surface inside the eye that contains photoreceptors and other neurons
• transduction


  the conversion of one form of energy to another
• cornea


  the transparent outer layer of the eye, whose curvature is fixed. bends light rays and is primarily responsible for forming the image on the retina
• refraction


  the bending of light rays by a change in the density of a medium, such as the cornea and lens of the eye
• lens


  a structure in the eye that helps focus an image on the retina
• ciliary muscle


  one of the muscles that control the shape of the lens inside the eye, focusing an image on the retina
• accommodation


  the process by which the ciliary muscles adjust the lens to bring nearby objects into focus
• myopia


  nearsightedness; the inability to focus the retinal image of objects that are far away
• extraocular muscle


  one of the muscles attached to the eyeball that controls its position and movements
• photoreceptor


  a neural cell in the retina that responds to light
• rod


  a photoreceptor cell in the retina that is most active at low levels of light
• cone


  any of several classes of photoreceptor cells in the retina that respond to color vision
• bipolar cell


  an interneuron in the retina that receives information from rods and cones and passes the information to retinal ganglion cells
• ganglion cell


  any of a class of cells in the retina whose axons form the optic nerve
• horizontal cell


  a specialized retinal cell that contacts both photo receptors and bipolar cells
• amacrine cell


  s specialized retinal cell that contacts both bipolar cells and ganglion cells and is especially significant in inhibitory interactions within the retina
• scotopic system


  a system in the retina that operates at low levels of light and involves the rods
• convergence


  the phenomenon of neural connections in which many cells send signals to a single cell
• photopic system


  a system in the retina that operates at high levels of light,, shows sensitivity to color, and involves the cones
• rhodopsin


  the photopigment in rods that responds to light
• pupil


  the opening, formed by the iris, that allows light to enter the eye
• iris


  the circular structure of the eye that provides an opening to form the pupil
• range fractionation


  the means by which sensory systems cover a wide range of intensity values, as each sensory cell specializes in just one part of the overall range of intensities
• visual field


  the whole area that you can see without moving your head or eyes
• visual acuity


  sharpness of vision
• fovea


  the central portion of the retina, which is packed with the highest density of photoreceptors and is the center of our gaze
• optic disc


  the region of the retina that is devoid of photoreceptors because ganglion cell axons and blood vessels exit the eye there
• blind spot


  the portion of the visual field from which light falls on the optic disc
• occipital cortex


  the cortex of the occipital lobe of the brain, corresponding to the visual area of the cortex
• optic tract


  the axons of retinal ganglion cells after they have passes the optic chiasm. most of these axons termiante in the lateral geniculate nucleus
• lateral geniculate nucleus


  the part of the thalamus that receives information form the optic tract and sends it to visual areas in the occipital cortex
• optic radiation


  axons from the lateral geniculate nucleus that terminate in the primary visual areas of the occipital cortex
• primary visual cortex


  aka V1, striate cortex, or area 17. the region of the occipital cortex where most visual information first arrives
• binocular


  referring to two-eyed processes
• extrastriate cortex


  visual cortex outside of the primary visual (striate) cortex
• topographic organization


  a mapping that preserves the point-to-point correspondence between neighboring parts of space
• scotoma


  a region of blindness within the visual fields caused by injury to the visual pathway or brain
• blindsight


  the paradoxical phenomenon whereby within a scotoma, a person cannot consciously perceive visual cues but may still be able to make some visual discrimination
• receptive field


  the stimulus region and features that affect the activity of a cell in a sensory system
• on-center bipolar cell


  a retinal bipolar cell that is excited by light in the center of its receptive field