Chapter 2 Flashcards
Wavelength
The distance between two successive peaks in a wave; different types of electromagnetic radiation are defined by their differences in wavelength
Electromagnetic radiation
A physical phenomena that is simultaneously both a wave and a stream of particles
Photon
Single particles of light, smallest possible quantity of electromagnetic radiation
Optic array
The spatial patterns of light rays, varying in brightness and color, entering your eyes from different locations in a scene
Field of view
Is the portion of the surrounding space you can see when your eyes are in a given position in their sockets
Acuity
Measure of how clearly fine detail is seen
Optical axis
Is an imaginary diameter line from the front to the back of the eye
Sclera
A tough protective coating whose visible portion is the whites of our eyes, and the transparent cornea
Choroid
Is the middle membrane, it lines the interior of the sclera and contains most of the blood vessels that supply the inside of the eye with the oxygen and nutrients
Retina
Inner membrane made up of neurons, including receptors that convert the light into neural signals
Cornea
Is a transporter membrane at the front of the eye, which sharply refracts light to focus it on the retina
Iris
Colored part of the eye, small donut shaped muscle with an opening in the middle known as the pupil
Pupillary reflex
The automatic process by which the iris contracts and relaxes to control the size of the pupil, in response to the relative brightness of light entering the eye
Anterior chamber
The space between the cornea and the iris
Posterior chamber
The space between the iris and the lens.
Aqueous humor
A clear thin fluid filling the anterior and posterior chambers of the eye
Vitreous chamber
The main interior portion of the eye filled with vitreous humor
Vitreous humor
A clear, somewhat gel-like fluid filling the vitreous chamber
Intraocular pressure
The pressure of the fluids in the 3 chambers of the eye
Lens
Transparent structure near the front of the eye that refracts the light passing through the pupil so that the light focuses properly on the retina
Focal length
The distance from a lens at which the image of an object is in focus when the object is far away from the lens
Diopters
Units used to express the power of a lens; diopters=1/(focal length)
Zonal fibers
Fibers that connect the lens to the choroid; they pull on the lens to change its shape
Ciliary muscles
Tiny muscles attached to the choroid; they relax and contract to control how the choroid pulls on the zonule fibers to change the shape of the lens
Luminance contrast
A difference in the intensity of illumination at adjacent retinal locations
Photopigment
A molecule with the ability to absorb light and initiate transduction
Spectral sensitivity
The degree to which a photopigment molecule absorbs light of different wavelengths
Isomers
Different possible shapes of molecules such as the all-trans retinal and 11-cis retinal shapes of photopigment molecules
Photoisomerization
A change in shape by a photopigment molecule from one isomer to another ( cis to trans) when a molecule absorbs a photon, initiates the transduction of light to a neural signal.
Operating range
The visual systems sensitivity to the range of light intensifies within the current scene; the visual system adjusts its operating range according to current conditions
Dark adaptation
The process of adjusting retinal sensitivity as the person moves from a bright environment to a darker one, the reverse process is called light adaptation
Rod monochromats
Individual sixth a very rare genetic disorder in which the retina develops with rods but without cones
Photopigment regeneration
The process whereby photopigment molecules change back into the 11-cis shape after photoisomerization
Convergence
A property of retinal circuits in which multiple photoreceptors send signals to one RGC
Spatial summation
A property of retinal circuits with convergence in which signals from photoreceptors in some small space on the retina summate to affect the response of the RGC in the circuit
Center surround receptive field
An RGC receptive field in which the center of the receptive field responds differently to stimulation than the surrounding portion of the field
On-center receptive fields
Receptive fields of RGC’s with center surround structure in which he RGC increase their firing rate when the amount of light striking the center of the receptive field increases relative to the amount of lights striking the surround
Preferred stimulus
The type of stimulus that produces a neurons maximum firing rate; for RGC’s with on-center receptive fields, the preferred stimulus is a spot of light that exactly fills the center of the receptive field
Off-center receptive fields
Receptive fields of RGC’s decrease their firing rate when the amount of light striking the center of the receptive field decreases relative to the amount of light striking the surround
Lateral inhibition
Inhibitory neural signals transmitted by horizontal cells in retinal circuits
Edge enhancement
Approves by which the visual system makes edges as visible as possible, facilitating perception of where one object or surface ends in the retinal image and another begins
