1. Sensation

2.  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  Adaptation ◦ The decreasing response of the sense organs as they’re exposed to a continuous level of stimulation

3.  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

4.  Stimulus: light waves ◦ Invisible (too short)  gamma rays, x-rays, ultraviolet rays ◦ Visible (just right)  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)  radar, FM, TV, shortwave, AM

6.  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

7.  Structure and function ◦ Vision: seven steps  image reversed  light waves  cornea  pupil  iris  lens  retina

8.  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.  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.  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.  Structure and function ◦ Retina  located at the very back of the eyeball; 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

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.  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.  Cones ◦ Photoreceptors that contain three chemicals called opsins ◦ Activated in bright light ◦ Allow us to see color ◦ Cones are wired individually to neighboring cells ◦ Allow us to see fine detail

17.  Visual pathways: eye to brain ◦ Optic nerve ◦ Primary visual cortex ◦ Visual association areas

19.  Visual pathways: eye to brain ◦ Optic 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.  Visual pathways: eye to brain ◦ Primary visual cortex  back of the occipital lobes is where primary visual cortex transforms nerve impulses into simple visual sensations ◦ Visual association areas  primary visual cortex sends simple visual sensations to neighboring association areas  damage to the visual association area = visual agnosia: difficulty in assembling simple visual sensations into more complex, meaningful images

22.  Making colors from wavelengths ◦ Sunlight is called white light because it contains all the light waves ◦ White light passes through a prism; separates light waves that vary in length ◦ Visual system transforms light waves of various lengths into millions of different colors ◦ Shorter wavelengths of violet, blue, green ◦ Longer wavelengths of yellow, orange, and red ◦ An apple is seen as red because reflection of longer light waves that brain interprets as red

24.  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

25.  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

26.  Color blindness ◦ Inability to distinguish 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  inherited genetic defect; mostly in males  trouble distinguishing red from green  two kinds of cones  see mostly shades of green

27.  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; amplitude ◦ Frequency  number of sound waves occurring within a second

28.  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 a second)

29.  Measuring sound waves ◦ Decibel: unit to measure loudness ◦ Threshold for hearing  0 decibels (no sound)  140 decibels (pain and permanent hearing loss)

31.  Outer, middle, and inner ear ◦ Outer ear  consists of three structures  external ear  auditory canal  tympanic membrane

32.  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

33.  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)

34.  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

36.  Outer, middle, and inner ear ◦ Middle ear  bony cavity sealed at each end by membranes that 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)

37.  Outer, middle, and inner ear ◦ Inner ear  contains two structures sealed by bone  cochlea: involved in hearing  vestibular system: involved in balance

38.  Cochlea ◦ Bony coiled exterior that resembles a snail’s shell ◦ Contains receptors for hearing ◦ Function is transduction ◦ Transforms vibrations into nerve impulses sent to the brain for processing into auditory information

40.  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 (meaningful melodies, songs, words, or sentences)

41.  Auditory cues ◦ Direction of sound  determined by brain; calculates slight difference in time it takes sound waves to reach the two ears ◦ Calculating pitch  frequency theory  applies only to low-pitched sounds  rate ate that nerve impulses reach the brain determines how low a sound’s pitch is  place theory  brain determines medium-to-higher-pitched sounds from the place on the basilar membrane where maximum vibration occurs

42.  Auditory cues ◦ Calculating loudness  brain calculates loudness primarily from the frequency or rate of how fast or how slow nerve impulses arrive from the auditory nerve

43.  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 ◦ Includes sensing the position of the head, keeping the head upright, and maintaining balance

44.  Motion sickness (sensory mismatch between information from the vestibular system) ◦ symptoms: feelings of discomfort, nausea, and dizziness in a moving vehicle ◦ head bouncing, but distant objects look fairly steady Meniere’s disease (malfunction of the semicircular canals of the vestibular system) – symptoms: dizziness, nausea, vomiting, spinning, and piercing buzzing sounds Vertigo (malfunction of the semicircular canals of the vestibular system) – symptoms: dizziness and nausea

45.  Taste ◦ Chemical sense because the stimuli are various chemicals ◦ Tongue ◦ Surface of the tongue ◦ Taste buds

46.  Tongue ◦ Five basic tastes  sweet  salty  sour  bitter  umami: meaty-cheesy taste

47.  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

48.  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

50.  Smell, or olfaction ◦ Steps for olfaction  stimulus  olfactory cells  sensation and memories  functions of olfaction

52.  Smell, or olfaction ◦ Stimulus  we smell volatile substances  volatile substances are released molecules in the air at room temperature  examples: skunk spray, perfumes, warm brownies; not glass or steel

53.  Smell, or olfaction ◦ Olfactory cells  receptors for smell located in a one-inch-square patch of tissue in the uppermost part of the nasal passages  olfactory cells are covered in mucus that dissolves volatile molecules and stimulates the cells  the cells trigger nerve impulses that travel to the brain, which interprets the impulses as different smells

54.  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  we can identify as many as 10,000 different odors  we stop smelling our deodorants or perfumes because of decreased responding (adaptation)

55.  Smell, or olfaction ◦ Functions of olfaction  one function: to intensify the taste of food  second function: to warn of potentially dangerous foods  third function: to elicit strong memories; emotional feelings

57.  Touch ◦ Includes pressure, temperature, and pain ◦ Beneath the outer layer of skin are a half-dozen miniature sensors that are receptors for the sense of touch ◦ Change mechanical pressure or temperature variations into nerve impulses that are sent to the brain for processing

59.  Receptors in the skin ◦ Skin ◦ Hair receptors ◦ Free nerve endings ◦ Pacinian corpuscle

60.  Skin ◦ Outermost layer ◦ Thin film of dead cells containing no receptors ◦ Just below are first receptors, which look like groups of thread-like extensions ◦ Middle and fatty layer ◦ Variety of receptors with different shapes and functions ◦ Some are hair receptors

61.  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

62.  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

63.  Brain areas ◦ Somatosensory cortex ◦ Located in the parietal lobe ◦ Transforms nerve impulses into sensations of touch, temperature, and pain

64.  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

66.  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

67.  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

68.  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 twirl or electrically stimulate the needles ◦ After 10 to 20 minutes of stimulation, patients often report a reduction in various kinds of pain