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SENSATION

SENSATION. dEF : the process by which our brain and nervous system receive input from the environment Our senses use transduction : transform one energy into another. VISION. VISIBLE LIGHT. The visible region of the electromagnetic spectrum (very limited in humans)

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SENSATION

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  1. SENSATION dEF: the process by which our brain and nervous system receive input from the environment Our senses use transduction: transform one energy into another

  2. VISION

  3. VISIBLE LIGHT • The visible region of the electromagnetic spectrum (very limited in humans) • Wavelength: distance from one peak to another • Amplitude: measurement of intensity

  4. STRUCTURE OF THE EYE • Cornea: outer layer; bends light toward center of eyeball • Iris: colored part; muscle that dilates and contracts to regulate light • Pupil: opening created by the iris • Lens: behind pupil; focuses images (visual accommodation) • Aqueous humor: chamber filled with watery fluid • Vitreous humor: jelly-like substance in eyeball

  5. RETINA • Light-sensitive layer in back of eye; contains photoreceptor cells • Rods: pr cells that detect black/white/gray; work for dim light and night vision • Cones: pr cells that function only in bright light • Rods and cones are responsible for transducing light energy

  6. CONES • Located in and around the Fovea (central part of the retina) • 3 types: red, green, blue • The more active, the more color perceived

  7. TRANSDUCTION OF LIGHT ENERGY AND PATH TO BRAIN • Rs and Cs fire, activate bipolar cells • Enough bipolar cells fire, then ganglion cells fire • Ganglion cells meet at optic disc • Axons of ganglion cells form the optic nerve • Signal travels to occipital lobe

  8. focusing • 6 muscles for each eye • Focus hits cones • Surrounding items hit rods

  9. Peripheral vision • Ability of the eye to see things on the side of our field of vision • Tunnel vision: absence of peripheral vision

  10. BLIND SPOT • Optic disc creates a “hole” in the retina • No visual input

  11. SACCADE • Reflexive, rapid movement of the eye • Fills in missing info from blind spot

  12. Dark adaptation • Ability for eyes to adapt to quickly darkening conditions • Rhodopsin: light-sensitive pigment in rods that allows adaptation

  13. VISUAL INFORMATION PROCESSING

  14. FEATURE DETECTORS • Specialized neurons that react to the strength of visual stimuli • Respond to shapes, angles, edges, lines, movement, color, form, and depth

  15. PARALLEL PROCESSING • Feature detectors reacting to stimuli simultaneously

  16. THEORIES OF COLOR VISION

  17. Trichromatic theory (IN THE EYE) • AKA: Young-Hemholtz Theory • 3 cone types: red, green, blue; work together to produce the range of colors we see • Color perceived depends on mix of cone types that are firing

  18. Opponent processing theory (IN THE BRAIN) • 3 opponent channels: red/green, blue/yellow, black/white • Light waves excite one color in the pair and inhibit the other • Afterimage: visual sensation that remains after the stimulus is removed

  19. SYNTHESIS • Both are correct but explain color vision at different levels

  20. Problems in vision • Visual acuity: sharpness of visual perception • Myopia: nearsightedness • Presbyopia: farsightedness • Astigmatism: irregularly shaped cornea • Cataracts: break down of protein in lens; creates cloudiness • Conjunctivitis: pink eye • Glaucoma: damages optic nerve; destroys vision

  21. Color blindness • Caused by a lack of short-, medium-, or long-wavelength cones in fovea • Genetic • Inability to distinguish red from green is most common • 8% of men; 1% of women

  22. hearing Audition: the process by which our ears process sound waves

  23. Sound waves • Vibrations of molecules • Amplitude=loudness • Decibels (dB)-intensity—for each 10 dB increase, loudness increases 10x • Pitch—note—affected by wavelength • Frequency--# of wavelengths/second; measured in hertz (Hz)

  24. Anatomy of the ear • Pinna: outer ear; collects sound waves • Auditory canal • Tympanic membrane: eardrum; conduction (vibrates) • Middle ear: contains auditory ossicles (malleus, incus, stapes) that concentrate vibrations on the cochlea’s oval window

  25. Inner ear---cochlea • Inner surface of cochlea (basilar membrane) resonates to different sounds in different locations • Hair cells (cilia) are on top • Cilia convert vibrations to nerve impulses; send to auditory nerve • Signal travels to thalamus, then to temporal lobe

  26. Theories of sound and hearing • Place theory: Herman von Hemholtz—specific locations on basilar membrane respond to different pitches; high-pitch in beginning, low-pitch toward end • Frequency theory: basilar membrane vibrates at the frequency of each pitch

  27. Synthesis • Both work • Frequency for sounds under 1000Hz • Both for 1000-5000Hz • Place for over 5000Hz

  28. Locating sound • Sound is more intense to the ear closest to the sound • Louder the sound, the closer it is

  29. Problems in hearing • Conductive hearing loss: poor transfer of sound from eardrum to inner ear (hearing aid) • Nerve deafness: damage to cilia or auditory nerve (cochlear implant) • Sensorineural hearing loss: damage to inner ear, auditory nerve, or auditory processing areas of the brain

  30. SMELL (olfaction) • Receptors in mucous membranes • Each receptor responds to specific chemicals • Odors are related to shape of molecules that create smell • Signal goes through amygdala, then to hippocampus

  31. Taste (gustation) • Papillae-taste receptors on tongue • Absorb chemical molecules • Signal routed through thalamus, then cortex • 5 taste sensations: sweet, salty, sour, bitter, umami

  32. Touch • Somesthetic senses: skin senses; light touch, pressure, pain, cold, warmth • Signals sent to thalamus then to corresponding part of somatosensory cortex (parietal lobe)

  33. BALANCE • Vestibular sense • Otolith organs—inner ear; sensitive to movement and acceleration • Semicircular canals: 3 fluid-filled tubes adjacent to cochlea; movement in fluid creates sense of where we are in space and balance

  34. MOVEMENT • Kinesthetic system: receptors in muscles, tendons, and ligaments • Procioperception: sense of our body in space

  35. ADAPTATION • Sensory adaptation: occurs when sensory receptors respond less to unchanging stimuli • Sensory habituation: perception of senses depend on how focused we are on them

  36. PAIN • Nociceptors • Visceral pain: originates in internal organs • Referred pain: felt on surface of body, away from origin point • Somatic pain: sharp, bright, fast; comes from skin, joints, muscles, or tendons • Gate control theory of pain: the more neurons that fire, the more intense the pain—on pain msg can block another

  37. Interactions among senses • McGurk Effect: interaction w/vision and hearing—illusion when the auditory component of one sound is paired w/visual component of another sound, creating a 3rd sound • Multimodal perception: our senses evolved in tandem

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