1. Sensation
Chapter 4

2. Sir Isaac Newton English physicist
Observed a ray of sunlight (white light)
broken up into the colors of the spectrum when it passed through a glass prism

3. Sensory Systems We experience the world through
Vision, hearing, taste, smell, and touch
Allows us to process information

4. Receptors and Stimuli Eye – wavelengths of light
Ear – vibrations of air molecules
Nose –molecules in the air
Tongue – chemicals in food
Skin – pressure/ temperature

5. Absolute Thresholds
The smallest amount of a stimulation necessary in order for it to be detected by our sensory system (VOCAB)
Vision – see a candle flame from 30 miles away
Hearing – hear a watch tick from 20 ft. away
Taste – 1 tsp. of sugar in 2 gal. of water
Smell – 1 drop of perfume in a 1000 sq ft.
Touch – wing of a bee falling on your cheek, 1 cm

6. How do we perceive?
Info. from the environment is taken in by the senses through receptors
Receptors bring the info. to the brain
Perception – organizes the information that we receive, so we can use it

7. How do we perceive? Sensations - based on stimuli from the environment
Sensory coding - way the message is sent to the brain
Through these codes, the brain then processes the information

8. Sensory Adaptation
When a particular stimulus is received over a period of time, you adapt to the stimulus (VOCAB)
Ex. When you are in a completely dark room, at first you can not see anything, then your eyes begin to adjust to the darkness and you can see

9. Vision and Light
Light is the only form of electromagnetic radiation the human eye can see
Other types of light are:
Gamma rays
Ultraviolet rays – move too slowly
Infrared rays – move too quickly
Radio waves

10. Vision and Light
Visible light is white light from the sun or light bulb
White light - different frequencies or wavelengths
Different wavelengths = different colors
Visible spectrum of colors
violet (shortest) to red (longest)

11. Color Spectrum
R O Y G B I V

12. How The Eye Responds to Light
Light first enters the cornea (transparent covering of the eye)
The image is then focused using the lens (behind the cornea)
Light then passes through the pupil (dark area in the center of the eye) which is surrounded by the iris (colored part of the eye)
The pupil dilates (gets bigger) in dim light
The pupil contracts (gets smaller) in bright light

13. How The Eye Responds to Light
The lens focuses the image on the retina (interior of the eye) by a process called accommodation. The retina consists of neurons called photoreceptors
The photoreceptors convert light into electrical activity (bringing the info. to the brain).
Rods – function in dim light
Cones – function in bright light, color

14. How The Eye Responds to Light
Optic nerve (where it leaves the eye) – no photoreceptors in this area (blind spot)
The photoreceptors send impulses to the optic nerve, which sends them to the visual cortex of the brain, which then interprets the image

15. Color
We see color because our eyes have different receptors for different wavelengths of light
Hue (color) – refers to a particular wavelength
Saturation – purity, richness, or intensity of color. (Red – high saturation, Pink – low saturation)
Brightness – amplitude or height

16. Trichromatic Theory Trichromatic – 3 color theory
3 types of cones
1. Red
2. Green
3. Blue
All colors result from a combination of these three

17. Opponent-Process Theory
Three types of receptors:
Each receptor is capable of responding to one of these, but not all
1. red-green
2. yellow-blue
3. black - white

18. Opponent-Process Theory
The colors from each pair oppose each other, they cannot be blended
The 4 primary colors (red, green, blue, yellow) can be mixed with colors from other pairs
This mixing creates all the colors of the visible spectrum

19. Color Blindness Color weakness Affects 8% of the male population
Less than 1% of the female population
Usually inherited from the maternal grandfather

20. Hearing and Sound Sound is created in our brain from external stimuli
An object generates sound waves when its vibrating causes vibrations in the air molecules around it
Sound waves – patterns of vibrations
Sound waves travel much slower than light waves

21. Hearing and Sound
Sound waves are picked up by our auditory system - when the vibration puts pressure on our eardrum (this causes vibrations within the ear)
When these impulses reach the brain, we interpret them as a specific sound

22. Characteristics of Sound
1. Pitch – how high or low a sound it
2. Timbre – quality/complexity of sound
3. Intensity – loudness of a sound, measure in decibels

23. Sound Waves and the Ear An object in motion will produce sound
Sound waves travel in all directions
You hear something when the sound wave (pattern of vibration) is detected by the receptors in the ear
The brain then translates these receptors into sounds

24. 3 Parts of the Ear 1. External – air conducts sound waves
2. Middle – bone conducts sound waves
Hammer, anvil, stirrup (vibrations of these bones transmit sound to the inner ear)
3. Inner – fluid conducts sound waves
Sound is transmitted in the cochlea (tube filled with fluid)

25. Auditory Nerve
Conveys neural impulses to the hearing areas of the cerebral cortex
Brain can determine where a sound is coming from

26. Deafness 1. Conduction Eardrums or middle ear bones do not vibrate
Sound waves are partially or completely prevented from entering the inner ear
Hearing aids help amplify sound waves so they can reach the inner ear

27. Deafness 2. Nerve Deafness 3. Stimulation Deafness
damage to the auditory nerve
Messages cannot reach the brain
3. Stimulation Deafness
Permanent hearing loss
Cochlea is damaged by prolonged exposure to very loud noise

28. Smell & Taste Chemical senses
Receptors in the nose respond to molecules in the air
Receptors for taste on the tongue and mouth respond to chemicals in foods

29. How do we taste food?
Taste buds (receptors) are located on the surface of the tongue and roof of the mouth
4 Primary taste qualities
1. Bitter
2. Sour
3. Salty
4. Sweet

30. How do we taste food?
The sense of smell is involved in experiencing taste

31. How do we smell? Receptors are located in the nose
The process of olfaction (smelling) begins when we inhale
A sensory code in the olfactory bulbs sends info. about the molecules to the brain

32. How do we smell? Animals use their sense of smell in selecting a mate
At appropriate times their bodies give off pheromones – molecules that attract the opposite sex

33. Touch, Pressure, Temperature & Pain
Somatic receptors
Found all over the body
Varies in different areas
Tongue, lips, face, hands – the greater # of receptors the more sensitive to stimuli
Pain receptors are also found inside the body

34. Pain Serves as a warning signal
Provides us with vital information about an illness

35. Pain Thresholds vary with each individual Low tolerance High tolerance
Never feel pain

36. How does the body alleviate pain?
Various types of drugs
Aspirin
Tranquilizers
Pain killers

37. How does the body alleviate pain?
Endorphins (natural)
Released by neurons in the upper spinal cord and several regions in the brain
Bind receptors in the brain – just like pain killers do

38. Gate Control Theory Built in gating mechanism in the spinal cord
Block neural impulses outside the brain
2 Types:
Large (fast conducting)
Small (slow conducting)

39. Gate Control Theory
A message sent in one pain fiber can close the “pain gate” to a message from the other fiber
If only one pain message gets to the brain – we feel less pain!

40. Acupuncture Ancient Chinese practice
Needles are inserted in the appropriate places in the body that affect the functioning of pain gates
When the doctor twirls the needles, this causes small, sharp pains, which, when carried by small fibers, close the gates to more intense or chronic pain.