1. Module 5 Sensation

2. THREE DEFINITONS Adaptation: –the decreasing response of the sense organs, the more they are exposed to a continuous level of stimulation Sensation versus perception: –relatively meaningless bits of information that result when the brain processes electrical signals that come from the sense organs –perceptions: –meaningful sensory experiences that result after the brain combines hundreds of sensations

3. THREE DEFINITONS (CONT.) eyes, ears, nose, skin, and tongue are complex, miniaturized, living sense organs that automatically gather information about your environment Transduction: –process in which a sense organ changes, or transforms, physical energy into electrical signals that become neural impulses, which may be sent to the brain for processing

4. 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

5. EYE: VISION (CONT.) Stimulus: Light Waves –Invisible—too short wave lengths too short gamma rays, x-rays, ultraviolet rays –Visible—just right Visible spectrum Particular segment of electromagnetic energy that we can see because these waves are the right length to stimulate receptors in the eye –Invisible—too long wave lengths longer Radar, FM, TV, shortwave, AM

6. EYE: VISION (CONT.)

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

8. EYE: VISION (CONT.) 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

9. EYE: VISION (CONT.) 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

10. EYE: VISION (CONT.) 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

11. EYE: VISION (CONT.) 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

12. EYE: VISION (CONT.)

13. Retina: –three layers of cells back layer contains two kinds of photoreceptors that begin the process of transduction change light waves into electrical signals rod located primarily in the periphery cone located primarily in the center of the retina called the fovea

14. EYE: VISION (CONT.) rods: –photoreceptor that contain a single chemical, called rhodopsin –activated by small amounts of light –very light sensitive –allow us to see in dim light –see only black, white and shades of gray

15. EYE: VISION (CONT.) cones: –photoreceptors that contain three chemicals called opsins –activated in bright light –allow us to see color –cones are wired individually to neighboring cells –allows us to see fine detail

16. EYE: VISION (CONT.)

17. Visual pathways: Eye to brain –Optic nerve –Primary visual cortex –Visual association areas

18. EYE: VISION (CONT.)

19. 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

20. EYE: VISION (CONT.) Visual pathways: eye to brain –Primary visual cortex the back of the occipital 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

21. EYE: VISION (CONT.) Color Vision –Trichromatic theory three different kinds of cones in the retina each cone contains one of the three different light- sensitive chemicals, called opsins each of the three opsins is most responsive to wavelengths that correspond to each of the three primary colors blue, green, red all colors can be mixed from these primary colors

22. EYE: VISION (CONT.) Opponent-Process Theory –Afterimage visual sensation that continues after the original stimulus is removed ganglion cells in retina and cells in thalamus respond to two pairs of colors—red-green and blue-yellow when excited, respond to one color of the pair when inhibited, respond to complementary pair

23. EYE: VISION (CONT.) Color Blindness –inability to distinguished two or more shades in the color spectrum –Monochromatic: total color blindness black and white result of only rods and one kind of functioning cone –Dichromatic: trouble distinguishing red from green two kinds of cones inherited genetic defect mostly in males See mostly shades of green

24. 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

25. EAR: AUDITION (CONT.) Loudness –subjective experience of a sound’s intensity –brain calculates loudness from specific physical energy (amplitude of sound waves) Pitch –subjective experience of a sound being high or low –brain calculates from specific physical stimuli –speed or frequency of sound waves –measured in cycles (how many sound waves in one second)

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

27. EAR: AUDITION (CONT.)

28. Outer, middle, and inner ear –Outer ear consists of three structures external ear auditory canal tympanic membrane

29. EAR: AUDITION (CONT.) 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

30. EAR: AUDITION (CONT.) 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)

31. EAR: AUDITION (CONT.) 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

32. EAR: AUDITION (CONT.)

33. 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)

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

35. EAR: AUDITION (CONT.) 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

36. EAR: AUDITION (CONT.)

37. 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

38. 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

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

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

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

42. 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 Flavor –combination of taste and smell

43. CHEMICAL SENSES (CONT.)

44. Smell, or olfaction –Steps for olfaction Stimulus Olfactory cells Sensation and memories Functions of olfaction

45. CHEMICAL SENSES (CONT.)

46. Smell, or olfaction –Stimulus we smell volatile substances volatile substances are released molecules in the air at room temperature example: –skunk spray, perfumes, warm brownies; not glass or steel

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

48. 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

49. 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

50. TOUCH Touch –includes pressure, temperature, and pain

51. TOUCH (CONT.)

52. Receptors in the skin –skin –hair receptors –free nerve endings –Pacinian corpuscle

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

54. 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

55. 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

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

57. 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

58. PAIN (CONT.)

59. 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

60. 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

61. PAIN (CONT.) Dread –connected to pain centers in brain –not the act itself that people fear –time waiting before event causes dread Acupuncture –trained practitioners insert thin needles into various points on the body’s surface and then manually twirls or electrically stimulates the needles –after 10-20 minutes of stimulation, patients often report a reduction in various kinds of pain