Warm up?

1. Warm up? • What was the term, we learned it yesterday, that describes the weakest amount of stimulus required to produce a sensation? • Absolute Threshold • For the human sense of taste it is one teaspoon of sugar dissolved in two gallons of water. • It is usually accepted that the absolute threshold is the level that produces a response 50% of the time.

2. The Senses

3. Vision • Most studied of all the senses • Provides us with a tremendous amount of information about our environment • Sizes, shapes, locations, textures, colors, etc.

4. How does vision occur? • Light enters the eye through the pupil and reaches a flexible structure called the lens, which focuses light on the retina. • Retina • Contains rods & cones which change light energy into neuronal impulses, which travel along the optic nerve to the brain

5. Rods & Cones • Cones • Require more light than rods • Work best in daylight • Sensitive to color • Rods • Require less light than cones • Work best at night • No color

6. Experiment • The outer part of the retina is covered exclusively by rods (no cones). To illustrate this, partner up into experimenters and participants. I will provide you with red, green, blue, and yellow markers. The participants should stare straight ahead at a fixed spot without moving their eyes. The experimenters should stand behind the participants and slowly move the marker from the back to the front of the participants head. Each participants should say when they can see the marker and when they can identify the color. Experimenters should record the results for each marker. • Hypothesis • Will you first see the color or the marker? • Will there be a color that you see sooner than the others?

7. Light • Visible light represents a small portion of the electromagnetic spectrum. • Electromagnetic Spectrum • Composed of waves of different length and frequency • Gamma, rays, X-rays, Ultraviolet rays • Can observe visible light with a prism • Prism breaks sunlight into a rainbow of colors

8. Color Deficiency • Color blindness • Happens when some or all of a person’s cones do not function properly • Several kinds of color deficiency • Most see some colors but some see none and view the world as a black and white movie • Hereditary condition that affects about 8% of men and less than 1% of women

9. Binocular Fusion • This is the combination of the images received by two eyes • The visual system receives two different images on the retinas • This difference is called Retinal disparity • Eraser Test with good binocular vision • Essential to sense of depth perception • Large retinal disparity means object is nearby, while a small disparity means the object is distant

10. Nearsightedness/Farsightedness • Perfectly shaped eyeballs mean perfect vision • Ted Williams, fighter pilots, etc. • Eyeball is too long • Nearsighted…you can see objects that are near • Eyeball is too short • Farsighted…you can see objects that are far • Can be corrected with eyeglasses and contact lenses

11. Hearing • How do we Hear? • Depends on vibrations in the air called sound waves • Sound waves pass through various bones until they reach the inner ear • Inner ear contains tiny hairlike cells that change sound vibrations into neuronal signals that travel through the auditory nerve to the brain

12. Decibels • Strength of sound is measured in decibels • Sounds humans can hear range upward from 0 -140 decibels (jet plane taking off) • Anything over 110 can damage hearing

13. Pitch • Depends on sound wave frequency • Low frequency • Produces deep bass sounds • High frequency • Produces shrill squeaks • Sources of sound can be located when your ears work together • Ear that receives the sound first

14. Deafness • Two Types: • Conduction deafness • Occurs when anything hinders the physical motion through the outer/middle ear or when bones of the middle ear cannot carry sound inward. • Can be helped with a conventional hearing aid

15. Sensorineural deafness • Occurs when the haircellsor auditory neurons are damaged • Can only be helped with a special hearing aid called a cochlear implant • Electronic device that is surgically implanted into the cochlea

16. Balance • Vestibular System • Controls the body’s sense of balance and located inside the inner ear • Overstimulation of the vestibular system can result in dizziness and motion sickness • Experienced through amusement park rides • Without your sense of balance you would be unable to walk without stumbling • Vertigo

17. Smell & Taste • Very closely related • The sensory experiences of sour, sweet, salty and bitter make up taste • The combining of taste, smell, and tactile information is known as flavor • Flavor is detected using taste buds • Much of taste is actually produced by the sense of smell • When your nose is blocked foods taste bland

18. Skin Senses • Responsible for providing the brain with 4 kinds of information: pressure, warmth, cold & pain • Varies from place to place on skin (fingers) • Pain • Makes it possible to prevent damage to your body • Gate control theory of pain says that we can lesson some pains by shifting our attention away from pain impulses or by sending other signals to compete with the pain signals • Rubbing an injured area

19. Body Senses • Kinesthesis • Sense of movement and body position • Cooperates with the vestibular and visual senses to maintain posture and balance • Without kinesthesis our movements would be jerky and uncoordinated • Walking w/out looking at our feet, surgery, playing the piano would all be impossible