Do Now Try to label the diagram of the eye Use your textbook and the terms on the right to help you Optic nerve Pupil Lens Retina Vitreous Iris Cornea

Vision The Visual System Color Vision and Theories

Vision Test!!! First stare continuously at the center of the upper square for about 20 seconds, then look at the dot in the lower square. Within a moment, a gray-and-white afterimage should appear inside the lower square

The Visual System Structures and Functions Cornea –Clear protective coating that covers the front of the eye –Where light enters the eye Pupil –Opening in the center of the eye to let light pass through Pupil Cornea Iris –Colored part of the eye –Contract in bright light (protects eye) –Expand in dim light (let in extra light)

The Visual System Structures and Functions Lens –Transparent, inside pupil –Focuses light on retina –Changes shape to see near vs. far Retina –Inner surface in back of eyeball –Contains receptor cells –Very center is called the fovea Retina Vitreous Optic Nerve LensPupil Cornea Iris

Find Your Blind Spot Place on the retina where the optic nerve enters the retina and where there are no receptor cells

The Visual System Receptor Cells Location = retina Sensitive to electromagnetic energy, primarily light Rods –Respond to intensities of light/dark –Night vision - sensitive to light –About 120 million Cones –Responsible for seeing colors –Found in fovea –About 8 million Bipolar cells –Specialized neurons connected to receptors

Do Now Fill out Receptor Cell info on packet page #1

The Visual System Adaptation Dark adaptation –Process by which rods and cones become more sensitive to darkness –Not enough light to activate cones CANNOT SEE COLOR Light adaptation –Process by which sensitivity of rods and cones decreases in bright light

This is called afterimage Sense experience that occurs after a visual stimulus has been removed

Pop Quiz!!! What do you see with? YOUR BRAIN

Color Vision Properties of Color Hues –Aspects of color that correspond to general color names like red, green, and blue Saturation –Vividness or richness of a hue –Forrest green, olive green, pale green, neon green, etc. Brightness –Based on the nearness of a color to white as opposed to black –Is the color more white or black?

Color Vision Theories Primary colors for light mixtures: red, green, blue Additive color mixing –Mixing light of different wavelengths to create new hue Subtractive color mixing –Mixing pigments –Concerned with what colors are absorbed and reflected Trichromatic theory –Perception of all colors is based on three color receptors (red, green, blue) in the retina Opponent-process theory –Color receptors come in pairs (yellow-blue, red-green, black- white) Trichromatic = normal vision Color blindness … dichromat and monochromat

Color Vision Fun Facts!!! Color is in the eye of the beholder Humans and most primates are trichromats Rodents and owls (nocturnal animals) are monochromats Bees can see ultraviolet light