Chapter 9 Key Terms and Definitions
Terms : Hide Images
| 5030733827 | vision | The sense of sight | 0 | |
| 5030733828 | retina | A thin layer of cells at the back of the eye that transduces light energy into neural activity | 1 | |
| 5030733829 | refraction | The bending of light rays that can occur when they travel from one transparent medium to another | 2 | |
| 5030733830 | pupil | The opening that allows light to enter the eye and strike the retina | 3 | |
| 5030733831 | iris | The circular, pigmented muscle that controls the size of the pupil in the eye | 4 | |
| 5030733832 | cornea | The transparent external surface of the eye | 5 | |
| 5030733833 | sclera | The tough outer wall of the eyeball; the white of the eye | 6 | |
| 5030733834 | extraocular muscle | A muscle that moves the eye in the orbit | 7 | |
| 5030733835 | conjunctiva | The membrane that folds back from the eyelids and attaches to the sclera of the eye | 8 | |
| 5030733836 | optic nerve | The bundle of ganglion cell axons that passes from the eye to the optic chiasm | 9 | |
| 5030733837 | optic disk | The location on the retina where optic nerve axons leaves the eye | 10 | |
| 5030733838 | macula | In the eye, a yellowish spot in the middle of the retina with relatively few large blood vessels; contains the fovea | 11 | |
| 5030733839 | fovea | The pit or depression in the retina at the center of the macula; in humans, the fovea contains only cone photoreceptors and is specialized for high-acuity vision | 12 | |
| 5030733840 | aqueous humor | The fluid between the cornea and the lens of the eye | 13 | |
| 5030733841 | lens | The transparent structure lying between the aqueous humor and the vitreous humor the enables the eye to adjust its focus to different viewing distances | 14 | |
| 5030733842 | ciliary muscle | A muscle that controls the shape of the eye's lens | 15 | |
| 5030733843 | vitreous humor | The jellylike substance filling the eye between the lens and the retina | 16 | |
| 5030733844 | diopter | A unit of measurement for the refractive power of the eye, the reciprocal of the focal distance | 17 | |
| 5030733845 | accommodation | The focusing of light by changing the shape of the eye's lens | 18 | |
| 5030733846 | pupillary light reflex | An adjustment by the pupil to different levels of ambient light; the pupil's diameter becomes larger in dim light and smaller in bright light, in repsonse to retinal inputs to brain stem neurons that control the iris | 19 | |
| 5030733847 | visual field | The total region of space viewed by both eyes when the eyes are fixated on a point | 20 | |
| 5030733848 | visual acuity | The ability of the visual system to distinguish between two nearby points | 21 | |
| 5030733849 | visual angle | A way to describe distance across the retina; an object that subtends and angles of 3.5° will form an image on the retina that is 1mm across | 22 | |
| 5030733850 | photoreceptor | A specialized cell in the retina that transduces light energy into changes in membrane potential | 23 | |
| 5030733851 | bipolar cell | In the retina, a cell that connects photoreceptors to ganglion cells | 24 | |
| 5030733852 | ganglion cell | A cell in the retina that receives input from bipolar cells and sends an axon into the optic nerve | 25 | |
| 5030733853 | horizontal cell | A cell in the retina of the eye that projects neurites laterally in the outer plexiform layer | 26 | |
| 5030733854 | amacrine cell | A neuron in the retina of the eye that projects neurites laterally in the inner plexiform layer | 27 | |
| 5030733855 | ganglion cell layer | A layer of the retina closest to the center of the eye, containing ganglion cells | 28 | |
| 5030733856 | inner nuclear layer | A layer of the retina of the eye containing the cell bodies of bipolar, horizontal, and amacrime cells | 29 | |
| 5030733857 | outer nuclear layer | A layer of the retina of the eye containing the cell bodies of photoreceptors | 30 | |
| 5030733858 | layer of photoreceptor outer segments | A layer of the retina farthest from the center of the eye containing the light-sensitive elements of the photoreceptors | 31 | |
| 5030733859 | inner plexiform layer | A layer of the retina of the eye, located between the ganglion cell layer and the inner nuclear layer; contains the neurites and synapses between bipolar cells, amacrine cells, and ganglion cells | 32 | |
| 5030733860 | outer plaxiform layer | A layer of the retina of the eye, between the inner nuclear layer and the outer nuclear layer; contains the neurites and synapses between photoreceptors, horizontal cells, and bipolar cells | 33 | |
| 5030733861 | rod photoreceptor | A photoreceptor in the retina containing rhodopsin and specialized for low light levels | 34 | |
| 5030733862 | cone photoreceptor | A photoreceptor in the retina containing one of three photopigments that are maximally sensitive to different wavelengths of light. Cones are concentrated in the fovea, specialized for daytime vision, and responsible for all color vision | 35 | |
| 5030733863 | dark current | The inward sodium current that occurs in photoreceptors in the dark | 36 | |
| 5030733864 | cyclic guanosine monophosphate (cGMP) | A second messenger formed from guanosine triphosphate by the action of the enzyme guanylyl cyclase | 37 | |
| 5030733865 | rhodopsin | The photopigment in rod photoreceptors | 38 | |
| 5030733866 | transducin | The G-protein that couples rhodopsin to the enzyme phosphodiesterase in rod photoreceptors | 39 | |
| 5030733867 | phosphodiesterase (PDE) | An enzyme that breaks down the cyclic nucleotide second messengers cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) | 40 | |
| 5030733868 | Young-Helmholtz trichromacy theory | The theory that the brain assign colors based on a comparison of the readout of the three types of cone photoreceptors | 41 | |
| 5030733869 | dark adaptation | The process by which the retina becomes more sensitive to light in dim light | 42 | |
| 5030733870 | light adaptation | The process by which the retina becomes less sensitive to light in bright light conditions | 43 | |
| 5030733871 | OFF bipolar cell | A bipolar cell of the retina that depolarizes in response to dark (light OFF) in the center of its receptive field | 44 | |
| 5030733872 | ON bipolar cell | A bipolar cell of the retina that depolarizes in response to light (light ON) in the center of its receptive field | 45 | |
| 5030733873 | receptive field | The region of a sensory surface (retina, skin) that, when stimulated, changes the membrane potential of a neuron | 46 | |
| 5030733874 | center-surround receptive field | A visual receptive field with a circular center region and a surround region forming a ring around the center; stimulation of the center produces a response opposite that generated by stimulation of the surround | 47 | |
| 5030733875 | M-type ganglion cell | A type of ganglion cell in the retina characterized by a large cell body and dendritic arbor, a transient response to light, and no sensitivity to different wavelengths of light; also called M cell | 48 | |
| 5030733876 | P-type ganglion cell | A type of ganglion cell in the retina characterized by a small cell body and dendritic arbor, a sustained response to light, and sensitivity to different wavelengths of light; also called P cell | 49 | |
| 5030733877 | nonM-nonP ganglion cell | A ganglion cell in the retina that is not of the M type or P type, based on cell morphology and response properties. Of the variety of cell types in this category, some are known to be sensitive to the wavelength of light | 50 | |
| 5030733878 | color-opponent cell | A cell in the visual system with an excitatory response to wavelengths of light of one color and an inhibitory response to wavelengths of another color; the color pairs that cancel each other are red-green and blue-yellow | 51 | |
| 5030733879 | parallel processing | The idea that different stimulus attributes are processed by the brain is parallel, using distinct pathways | 52 |
