The Senses

1. The Senses Chapter 8-2

2. From A Second Way of Knowing: The Riddle of Human Perception by Edmund Blair Bolles, 1991 Seeing in the Dark Sit yourself in total darkness, a space so dark you cannot see your hand before your face. Now hold your hand before your face and move it from side to side. You see your hand in motion.

3. vision • Most studied sense

4. Vision Parts • Pupil • Lens • Retina • Optic nerve

6. pupil • The opening in the iris that regulates the amount of light entering the eye

7. lens • A flexible, transparent structure in the eye that changes its shape to focus light on the retina

8. retina • The innermost coating of the back of the eye, containing the light-sensitive receptor cells • Light sensitive receptor cells: • Rods • Better for night vision • 75-150 million in the eye • Cones • Better in daylight • 6-7 million in the eye • See color

9. Optic nerve • The nerve that carries impulses from the retina to the brain

10. vision How it works: • Light enters the eye through the pupil • Light reaches the lens • The lens focuses the light onto the retina • The retina’s rods and cones change the light energy into neuronal impulses • Impulses travel over the optic nerve to the brain and into the occipital lobe

12. light • Form of electromagnetic radiation • Colors are different wavelengths of light • We see color after light hits objects and bounce back to us at different speeds/frequencies

13. The Electromagnetic Spectrum

16. Color deficiency • When some or all of a person’s cones do not function properly • Affects 8% of American men, less than 1% of women • Hereditary • Carried in female genes Ex. • Hard to tell the difference between red and green • Hard to tell the difference between yellow and green • Color blind (see in black and white and shades of grey)

18. Binocular Fusion • The process of combining the images received from the two eyes into a single, fused image • 2 eyes get two messages/images, the brain makes both of these messages/images into one

19. Retinal disparity • The difference between the images stimulating each eye • Each eye has a slightly different view of things • Important for depth perception • If there is a large retinal disparity, the object is close • If there is a small retinal disparity, the object is far away

20. Nearsightedness & farsightedness • Perfect shaped eyeballs = perfect vision • Little too long eyeballs = nearsighted • Close clear • Far away blurry • Too short eyeball = farsighted • Close blurry • Far away clear

21. hearing • Depends on vibrations of the air (sound waves) How it works: • Sound waves pass through various bones • Sound waves reach the inner ear • Tiny hairs in the inner ear move back and forth • Tiny hairs change sound vibrations into neuronal signals • Neuronal signals travel through the auditory nerve to the brain

23. Auditory nerve • The nerve that carries impulses from the inner ear to the brain, resulting in the sensation of sound

24. loudness • Determined by the amplitude (height) of sound waves • Higher the amplitude, the louder the sound

25. decibels • The strength or sound pressure energy measurement • Decibel range: 0-140 decibels

27. pitch • Sound-wave frequency – rate of the vibration of the medium through which the sound wave is transmitted • Low frequencies = bass sounds • High frequencies = shrill squeaks

28. Locating sound • In both ears, but in the closer ear first

29. The pathway of sound • Outer ear • receives sound waves • Earflap directs sound down the auditory canal (a short tube) • Air in the canal vibrates and makes the eardrum vibrate

30. The pathway of sound • Middle ear • Air filled cavity • Has 3 tiny bones • Hammer • Anvil • Stirrup • Vibrate and push the cochlea

31. The pathway of sound • Inner ear • Cochlea • Bony tube that contains fluids and neurons • Pressure against the cochlea makes the liquid inside the cochlea move • Tiny hairs inside the cochlea feel the motion • The hairs are attached to sensory cells • Sensory cells turn the sound vibrations into neuronal impulses

33. Deafness Types: • Conduction • When anything hinders the physical motion of the ear • Hearing aids can work • Sensorineural • Damage to the cochlea, hair cells, or the auditory neurons • Cochlear implants can work

34. balance • Regulated by the vestibular system in the inner ear

35. Vestibular system • three semicircular canals that provide the sense of balance, located in the inner ear and connected to the brain by a nerve • Hair cells project into the fluid in each canal • When you turn your head, canals move, and fluid will move and bend the hairs

36. Smell & Taste • Chemical senses

37. Smell How it works: • Chemical molecules come into contact with the smell receptors in your nose • Molecules enter in vapors that reach a special membrane in the upper part of the nasal passage where the small receptors are • Receptors send messages about smells through the olfactory nerve to the brain

38. Olfactory nerve • The nerve that carries smell impulses from the nose to the brain • Caries messages about smell

39. Taste • Chemicals stimulate receptors in the taste buds on your tongue • Taste information is sent to the brain as well as information about texture & temperature • Flavor = combining taste, smell and tactile sensations • Relies heavily on smell • 4 primary tastes: • Sour • Salty • Bitter • sweet

40. Skin Senses • Skin receptors provide at least 4 types of information: • Pressure • Warmth • Cold • Pain • Where there are more receptors, there is more feeling

41. Perceptions of Pain • Pain comes from many different stimuli • Types of pain: • Sharp – localized pain you may feel immediately after an injury • Dull – generalized pain you may feel later

42. Gate Control Theory of Pain • We can lessen some pains by shifting our attention away from the pain impulses OR by sending other signals to compete with the pain signal

43. Body Senses • Kinesthesis – the sense of boy movement and body position • Works with vestibular and visual senses to maintain posture and balance