Vision and Color Vision Flashcards

Flashcards covering the visual system: light as energy, eye anatomy, visual acuity, refractive errors, retinal photoreceptors, neural pathways, lateral inhibition, dark adaptation, and color vision theories.

What energy signal is involved in visual sensation and perception?

Light, an electromagnetic radiation that travels in wavelengths and hits the receptors in the eye.

What sequence of eye components does light pass through before reaching the retina?

Cornea → pupil (through the iris) → lens; the lens focuses light onto the retina and inverts the image.

What happens to the image as it passes through the lens?

The image is turned backwards and upside down and focused onto the retina.

Where is the blind spot (optic disk) located and why can't it see an image there?

At the optic disk, the point where the optic nerve exits the retina; there are no photoreceptors, so images on this spot cannot be seen.

What is visual acuity?

The sharpness with which a person can see objects and distinguish details.

What is myopia (nearsightedness) and what causes it?

The focus point falls in front of the retina; caused by cornea/lens bending light too much or an eyeball that is too long; distant objects appear blurry.

What is hyperopia (farsightedness) and what causes it?

The focus point falls behind the retina; caused by an eyeball that is too short; near objects appear blurry.

Where are rods and cones located and what are their roles?

Rods are distributed throughout the retina; cones are concentrated in the fovea; rods mediate night vision; cones mediate daylight/color vision and provide sharpness.

Which photoreceptors are most sensitive in dim light and which provide color vision?

Rods handle dim light; cones provide color vision and daylight vision.

Which photoreceptors provide sharpness and detail in vision?

Cones provide more sharpness and detail than rods in bright light.

Describe the basic retinal neural pathway from photoreceptors to the brain.

Photoreceptors → bipolar cells → ganglion cells → optic nerve; axons exit at the optic disk (blind spot) and carry signals to the brain.

What is lateral inhibition?

A competitive interaction between ON-center and OFF-center receptive fields that enhances contrast and edges.

What are ON-center and OFF-center receptive fields?

Retinal regions where light increases (ON) or decreases (OFF) activity, forming center-surround receptive fields.

What is dark adaptation?

Adjustment to darkness; photopigments bleach; thresholds for vision drop; cones adapt first, rods adapt more slowly and continue improving night vision.

What are the three aspects of color vision?

Hue, saturation, and brightness.

How does color relate to wavelength and hue?

Color is largely determined by wavelength; longer wavelengths appear red, shorter wavelengths appear violet.

What does the trichromatic theory propose?

There are three types of cones (sensitive to red, green, and blue); colors are produced by differing activations of these cones.

What does the opponent-process theory propose?

Color processing involves antagonistic pairs: red-green, yellow-blue, and black-white; explains afterimages.

Why are both the trichromatic and opponent-process theories used together?

Trichromatic theory explains detection of wavelengths in the retina; opponent-process explains processing in the pathways; both are needed for full color vision.

What is color blindness?

A deficiency or weakness in color vision, often red-green; partial color blindness is common.

Where does electrochemical visual information go after leaving the retina?

To the occipital lobes of the brain for initial processing into visual perception.

What is the optic disk?

The point at which the optic nerve exits the eye; the blind spot.

What is the fovea and its role?

A small region in the retina rich in cones responsible for sharp central vision.

What is the role of the cornea, iris, pupil, and lens in vision?

Cornea begins focusing light; iris controls pupil size; pupil is the opening for light; lens fine-tunes focus onto the retina.