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
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: 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 Sensorineural
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