Ch. 10.2 Properties of the Retinα Shape Many Aspects of Our Vision Flashcards
How does the visual system deal with a large range of intensities of light?
- Adjusting the size of the pupil
- range fractionation
- photoreceptor adaptation
What is photoreceptor adaptation?
The tendency of rods and cones to adjust their light sensitivity to match ambient levels of illumination
What is range fractionation?
The handling of different intensities by different receptors - some with high sensitivity (rods) and others with low sensitivity (cones).
What is the visual field?
The whole area that you can see without moving your head or eyes.
What is visual acuity?
The sharpness of vision (it is especially fine in the center of the visual field and falls off rapidly toward the periphery).
What is the fovea?
The central region of the eye (it has a dense concentration of cones so therefore, provides high visual acuity)
What is the optic disc?
The region of the retina devoid of receptor cells because ganglion cell axons and blood vessels exit the eyeball there. There are no photoreceptors here so there is a blind spot.
What is a blind spot?
The portion of the visual field from which light falls on the optic disc. Because there are no receptors in this region, light striking it cannot be seen.
What do you know about cones?
- Photoreceptor
- responsible for color vision
- concentrated in the center of the retina
- Helps us see fine detail
- low sensitivity
What so you know about rods?
- photoreceptor
- concentrated in the outer areas of the retina
- give us peripheral vision
- High sensitivity
- Give us good vision in low light
What is saccades?
Fast movements of the eyes that present various parts of the visual scene to the fovea. When we fix our gaze, small saccades that we are unaware of happen.
This stops photoreceptor adaptation.
What is lateral inhibition?
The phenomenon by which interconnected neurons inhibit their neighbors, enhancing contrast at the edges of regions.
