1. Module 5
Sensation

2. EYE: VISION Structure and function eyes perform two separate processes
first: gather and focus light into precise area in the back of eye
second: area absorbs and transforms light waves into electrical impulses
process called transduction

3. p95 EYE

4. EYE: VISION Structure and function Vision: 7 steps Image reversed
Light waves
Cornea
Pupil
Iris
Lens
Retina

5. EYE: VISION Structure and function Image reversed
In the back of the eye, objects appear upside down.
somehow the brain turns the objects right side up
Light waves
light waves are changed from broad beams to narrow, focused ones

6. EYE: VISION Structure and function Cornea
rounded, transparent covering over the front of your eye
Pupil
round opening at the front of the eye that allows light waves to pass into the eye’s interior

7. EYE: VISION Structure and function Iris
circular muscle that surrounds the pupil and controls the amount of light entering the eye
Lens
transparent, oval structure whose curved surface bends and focuses light waves into an even narrower beam

8. EYE: VISION Structure and function Retina
located at the very back of the eyeball, is a thin film that contains cells that are extremely sensitive to light
light sensitive cells, called photoreceptors, begin the process of transduction by absorbing light waves

9. p96 RETINA

10. EYE: VISION Visual pathways: Eye to brain Optic nerve
Primary visual cortex
Visual association areas

11. p97 VISUAL SYSTEM

12. EYE: VISION Visual pathways: eye to brain Optic nerve
nerve impulses flow through the optic nerve as it exits from the back of the eye
the exit point is the “blind spot”
the optic nerves partially cross and pass through the thalamus
the thalamus relays impulses to the back of the occipital lobe in the right and left hemisphere

13. EYE: VISION Visual pathways: eye to brain Primary visual cortex
the backs of the occipitals lobes is where primary visual cortex transforms nerve impulses into simple visual sensations
Visual association areas
the primary visual cortex sends simple visual sensations to neighboring association areas

14. EAR: AUDITION Stimulus: Sound waves stimuli for hearing (audition)
ripples of different sizes
Sound waves travel through space with varying heights and frequency.
Height
distance from the bottom to the top of a sound wave
called amplitude
Frequency
number of sound waves occurring within one second

15. EAR: AUDITION Measuring sound waves decibel: unit to measure loudness
threshold for hearing:
0 decibels (no sound)
140 decibels (pain and permanent hearing loss

16. p101 DECIBEL CHART

17. EAR: AUDITION Outer, middle, and inner ear Outer ear
consists of three structures
external ear
auditory canal
tympanic membrane

18. EAR: AUDITION Outer, middle, and inner ear Outer ear external ear
oval shaped structure that protrudes from the side of the head
function
pick up sound waves and then send them down the auditory canal

19. EAR: AUDITION Outer, middle, and inner ear Outer ear auditory canal
long tube that funnels sound waves down its length so that the waves strike the tympanic membrane (ear drum)

20. EAR: AUDITION Outer, middle, and inner ear Outer ear tympanic membrane
taut, thin structure commonly called the eardrum
Sound waves strike the tympanic membrane and cause it to vibrate

21. p102 EAR DIAGRAM

22. EAR: AUDITION Outer, middle, and inner ear Middle ear
bony cavity sealed at each end by membranes.
the membranes are connected by three tiny bones called ossicles
hammer, anvil and stirrup
hammer is attached to the back of the tympanic membrane
anvil receives vibrations from the hammer
stirrup makes the connection to the oval window (end membrane)

23. EAR: AUDITION Outer, middle, and inner ear Inner ear
contains two structures sealed by bone
cochlea: involved in hearing
vestibular system: involved in balance

24. EAR: AUDITION
Cochlea
bony coiled exterior that resembles a snail’s shell
contains receptors for hearing
function is transduction
transforms vibrations into nerve impulses that are sent to the brain for processing into auditory information

25. EAR: AUDITION Auditory brain areas sensations and perceptions
two step process occurs after the nerve impulses reach the brain
primary auditory cortex
top edge of temporal lobe
transforms nerve impulses into basic auditory sensations
auditory association area
combines meaningless auditory sensations into perceptions, which are meaningful melodies, songs, words, or sentences

26. VESTIBULAR SYSTEM: BALANCE
Position and balance
vestibular system is located above the cochlea in the inner ear
includes semicircular canals
bony arches set at different angles
each semicircular canal is filled with fluid that moves in response to movements of your head
canals have hair cells that respond to the fluid movement
function of vestibular system
include sensing the position of the head, keeping the head upright, and maintaining balance

27. CHEMICAL SENSES
Taste
chemical sense because the stimuli are various chemicals
tongue
surface of the tongue
taste buds

28. CHEMICAL SENSES (CONT.)
Tongue
Five basic tastes
sweet
salty
sour
bitter
umami: meaty-cheesy taste

29. CHEMICAL SENSES (CONT.)
Surface of the tongue
chemicals, which are the stimuli for taste, break down into molecules
molecules mix with saliva an run into narrow trenches on the surface of the tongue
molecules then stimulate the taste buds

30. CHEMICAL SENSES (CONT.)
Taste buds
shaped like miniature onions
receptors for taste
chemicals dissolved in saliva activate taste buds
produce nerve impulses that reach areas of the brain’s parietal lobe
brain transforms impulses into sensations of taste

31. CHEMICAL SENSES (CONT.)
Smell, or olfaction
Olfaction
called a chemical sense because its stimuli are various chemicals that are carried by the air
Function of olfaction
receptors, through transduction, transform chemical reactions into nerve impulses

32. p107 OLFACTORY BULB

33. CHEMICAL SENSES (CONT.)
Smell, or olfaction
Steps for olfaction
Stimulus
Olfactory cells
Sensation and memories
Functions of olfaction

34. CHEMICAL SENSES (CONT.)
Smell, or olfaction
Stimulus
we smell volatile substances
volatile substances are released molecules in the the air at room temperature
example:
skunk spray, perfumes, warm brownies; not glass or steel

35. CHEMICAL SENSES (CONT.)
Smell, or olfaction
Olfactory cells
receptors for smell are located in a I-inch-square patches of tissue in the uppermost part of the nasal passages.
olfactory cells are covered in mucus
which volatile molecules dissolve and stimulate the cells
the cells trigger nerve impulses that travel to the brain
which interprets the impulses as different smells

36. CHEMICAL SENSES (CONT.)
Smell, or olfaction
Sensations and memories
nerve impulses travel to the olfactory bulb
impulses are relayed to the primary olfactory cortex
cortex transforms nerve impulses into olfactory sensations
Can identify as many as 10,000 different odors
we stop smelling our deodorants or perfumes because of decreased responding
called adaptation

37. CHEMICAL SENSES (CONT.)
Smell, or olfaction
Functions of olfaction
one function: to intensify the taste of food
second function: to warn of potentially dangerous foods
third function: elicit strong memories; emotional feelings

38. TOUCH
Touch
includes pressure, temperature, and pain

39. p108 SKIN

40. TOUCH (CONT.) Receptors in the skin skin hair receptors
free nerve endings
Pacinian corpuscle

41. TOUCH (CONT.) Skin outermost layer
thin film of dead cells containing no receptors
just below, are fist receptors which look like groups of threadlike extensions
middle and fatty layer
variety of receptors with different shapes and functions
some are hair receptors

42. TOUCH (CONT.) Hair receptors
free nerve endings wrapped around the base of each hair follicle
hair follicles fire with a burst of activity when first bent
If hair remains bent for a period of time, the receptors will cease firing.
sensory adaptation
example: wearing a watch

43. TOUCH (CONT.) Free nerve endings
near bottom of the outer layer of skin
have nothing protecting or surrounding them
Pacinian corpuscle
in fatty layer of skin
largest touch sensor
highly sensitive to touch
responds to vibration and adapts very quickly

44. TOUCH (CONT.) Brain areas somatosensory cortex
located in the parietal lobe
transforms nerve impulses into sensations of touch temperature, and pain

45. PAIN
What causes pain?
pain: unpleasant sensory and emotional experience that may result from tissue damage, one’s thoughts or beliefs, or environmental stressors
pain results from many different stimuli

46. p112 BRAIN PAIN

47. PAIN (CONT.) How does the mind stop pain? gate control theory of pain
nonpainful nerve impulses compete with pain impulses in trying to reach the brain
creates a bottleneck or neutral gate
shifting attention or rubbing an injured area decreases the passage of painful impulses
result: pain is dulled

48. PAIN (CONT.) Endorphins
chemicals produced by the brain and secreted in response to injury or severe physical or psychological stress
pain reducing properties of endorphins are similar to those of morphine
brain produces endorphins in situations that evoke great fear, anxiety, stress or bodily injury as well as intense aerobic activity