Chapter 7 Flashcards
Retina
Receptive surface inside the eye that contains photoreceptors and other neurons
Transduction
Conversion of one form of energy to another, ex. light to neuron signals
Cornea
Transparent outer layer of the eye, fixed curvature. Bends light rays and is primarily responsible for forming the image on the retina
Refraction
Bending of light rays by the change in density of a medium. Ex. the cornea and lens of the eye.
Lens
Structure in the eye that helps focus the image on the retina
Ciliary muscles
One of the muscles that controls the shape of the lens inside the eye, focusing the image on the retina
Accommodation
Process by which ciliary muscles adjust the lens to focus a sharp image on the retina.
Myopia
Nearsightedness, unable to focus retinal image of objects that are far away. Eyeball is too long, and image is blurred on retina.
Extraocular muscle
Muscle that controls the position and movement of eyeball
Photoreceptor
Neural cell in retina that responds to light
Rod
Photoreceptor in retina that is most active at low levels of light
Cone
Photoreceptor of several classes in the retina that are responsible for color vision
Bipolar Cell
Interneuron in retina that receives information from rods and cones and passes the information to retinal ganglion cells.
Ganglion Cells
Any of a class of cells in the retina whose axons form the optic nerve
Optic Nerve
Cranial Nerve II, the collection of ganglion cells axon that extend from the retina to the brain
Horizontal Cell
Specialized retinal cells that contacts both photoreceptors and bipolar cells
Amacrine Cells
Specialized retinal cells that contacts both bipolar cells and ganglion cells and is especially significant in inhibitory interactions within the retina.
Scotopic system
System in retina that operates at low levels of light and involves the rods
Convergence
Phenomenon of neural connections in which many cells send signals to one cell
Photopic System
System in the retina that operates at high levels of light, shows sensitivity to color, and involves the cones
Rhodopsin
Photopigment in rods that responds to light
Pupil
Opening, formed by the iris, allows light to enter the eye
Iris
Circular structure of the eye that provides an opening to form pupil
Range Fractionation
Means by which sensory systems cover a wide range of intensity value, as each sensory receptor cell specializes in just one part of the overall range of intensities.
Photoreceptor adaptation
Tendency of rods and cones to adjust their light sensitivity to match current levels of illumination
Visual acuity
Sharpness of vision
Fovea
Central portion of the retina, packed with the highest density of photoreceptor and is the center of our gaze
Optic disc
region of the retina that is devoid of receptor cells because ganglion cell axons and blood vessels exit the eyeball there
Blind Spot
Portion of the visual field from which light falls on the optic disc
Occipital Cortex
“Visual cortex”. The cortex of the occipital lobe of the brain, corresponding to the primary visual area of the cortex
Optic Chiasm
Point at which parts of the two optic nerves cross the midline
Optic Tract
Axons of the retinal ganglion cells after they have passed the optic chiasm. Most terminate in the lateral geniculate nucleus
Lateral Geniculate Nucleus (LGN)
Part of the thalamus that receives information from the optic tract and sends it to visual areas of the occipital cortex
Optic Radiation
Axons from the lateral geniculate nucleus that terminate in the primary visual areas in the occipital cortex
Primary Visual Cortex (V1)
“striate cortex or area 17” region of the occipital cortex where most visual information first arrives. features a prominent striation, corresponding to the convergent binocular inputs.
Extrastriate cortex
visual cortex outside of the primary visual (striate) cortex
Visual Field
Whole are that you can see without moving your head or eyes.
Topographic projection
Mapping that preserves the point-to-point correspondence between neighboring parts of space.
Scotoma
Region of blindness within visual fields, caused by injury to the visual pathway or brain
Blindsight
Paradoxical phenomenon whereby, within scotoma, a person cannot consciously perceive visual cues but may still be able to make some visual discrimination
Receptive Field
Stimulus region and features that affect the activity of a cell in a sensory system
On-center bipolar cell
Retinal bipolar cell that is excited by light in the center of its receptive field
Off-center bipolar cell
Retinal bipolar cell that is inhibited by light in the center of its receptive field
On-center ganglion cell
Retinal ganglion cell that is activated when light is presented to the center, rather than periphery of the cells receptor field
Off-center ganglion cell
Retinal ganglion cell that is activated when light is presented to the periphery, rather than the center of the cells receptor field
On-center/Off-surround
Concentric receptor field in which stimulation of the center excites the cell of interest while stimulation of the surround inhibits it
Off-center/On-surround
Concentric receptive field in which the stimulation fo the center inhibits the cell of interest while stimulation of the surrounding excites it.
Lateral Inhibition
Phenomenon by which interconnected neurons inhibit their neighbors, producing contrast at the edges of regions.
