1. Sensation and perception
Chapter 4

2. ThEcOwgAvecOla
All incoming information must be interpreted by the brain!
“.rat eht saw tac ehT”
We often see what we want to see or what we expect to see!

3. Sensation The process of receiving information from the environment.
Seeing, touching, tasting, smelling, hearing

4. Perception
Assembling and organizing sensory information to make it meaningful.

5. Vision Dominates the human senses! We believe what we see first!
Will these taste funny to you?

6. Light Light moves as waves.
Light starts out as white and we see “color” as it hits various objects and bounces back to us at different speeds.
We have different receptors for different wave lengths.
We can’t see ultraviolet waves because they move too fast for our receptors.
Infrared moves too slow for our receptors.
Snowflakes are white because they have many flat surfaces and light bounces off without breaking up.
Water molecules are strangely shaped and complex, so they absorb the energy at the red end of the spectrum and only green and blue rays reflect back.

8. Structures of the Eye

9. Structures of the Eye
Cornea: clear outer anterior covering, the “window of the eye”
Iris: colored part, muscle that controls pupil size in response to light and psychological factors such as something unpleasant, desire, or fear
Pupil: opening
Lens: just behind pupil, focus light to the back of the eye where receptors are located
Retina: inner layer filled with receptors
Blind spot: area where optic nerve leaves the eye-no receptors

10. More Eye Structures Sclera: whites of the eyes, tough outer covering
Macula Lutea: site of best vision
Ciliary body: muscle that bends the lens
Suspensory Ligaments: holds lens in place
Anterior Chamber: before the lens, filled with watery fluid (aqueous humor), nourishes, drainage problems cause Glaucoma
Posterior Chamber: after the lens, filled with thick, jelly-like fluid (vitreous humor), helps keep eye shape

12. Light Receptors
Converts light waves into
electrical signals.
Rods: black and white, night vision, peripheral vision, turn on in dim light, no color chemicals, more sensitive to violet-purple wave lengths
Cones: colors and bright light, turn off in dim light, different cones pick up different light wave lengths, have color chemicals

13. Color Vision
All the colors we see are red, blue, and green, or a mixture of the 3
The brain mixes the different wave lengths and we see specific colors

14. Color Defects Color Blindness: inability to see certain colors
Most color blindness is red/green

16. After Images
When you stare at a colored object for a minute or so, the chemicals for the colors you are seeing (in the cones) will be partially used up to send electrical impulses.
To balance out the chemicals, when you look away at a white piece of paper, the unused cones will fire to regain balance.