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Sensation

Sensation. Stimulation of a sensory receptor gives rise to neural impulses which give awareness to conditions inside or outside the body. Psychophysics. Study of the relationship between physical stimuli and the behavior or mental experiences the stimuli evoke Founder –Gustav Fechner

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Sensation

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  1. Sensation • Stimulation of a sensory receptor gives rise to neural impulses which give awareness to conditions inside or outside the body

  2. Psychophysics • Study of the relationship between physical stimuli and the behavior or mental experiences the stimuli evoke • Founder –Gustav Fechner • Absolute threshold • Smallest unit or minimal amount of physical energy needed to produce a sensory experience. Amount of energy related to intensity of experience.

  3. Psychophysics • Sensory Adaptation • Diminishing responsiveness of sensory systems to prolonged stimulus input. (stinky room)

  4. Absolute threshold • Smallest unit or minimal amount of physical energy needed to produce a sensory experience. Amount of energy related to intensity of experience.

  5. Psychophysics • Psychometric function • A graph that shows the % of detections at each stimulus intensity

  6. Psychophysics • Response bias-favor responding in a particular way. • Signal detection theory (SDT) • Helps combat response bias • Initial sensory process • Separate decision process

  7. Psychophysics • Difference thresholds • Smallest physical difference between 2 stimuli that can still be recognized as a difference • Just noticeable difference (JND) • Weber’s law • Size of a difference thresholds is proportional • Lmm/10mm=.1; 2mm/20mm=.1 • ChangeI/I=K

  8. Sensory Physiology • Biological mechanisms (eye, mouth, ear) convert physical events into neural events. • Sensory receptors • Specialized cells that convert physical signals into cellular signals that are processed by the nervous system • Transduction • Transforming one energy into another sound or light- neural impulses

  9. Visual System (eye) • Pupil – opening in iris-light passes through • lens – focuses light • Accommodation-the ciliary muscles changing the thickness of lens • Retina-layer of photoreceptors at the back of the eye-converts light into nerve energy

  10. Visual System • Photoreceptors • Rods-active in dim light, lack color • Cones-normal viewing-color • Foveo-all cones- best viewing • Bipolar cells-combine impulses from receptors send to ganglion cells • Ganglion cells-integrates into a single fire rate • Amacrine+horizontal cells-integrate info across retina

  11. Visual Systems • Primary visual cortex-region in occipital lobe in which visual info is processed • Optic nerve-axons of ganglion cells that carry info from the eye to brain • Optic tracts-deliver info to 2 clusters • 2 sides of brain w/ same pattern on each side

  12. Visual System • Color-spectrum (wave lengths) • Hue-captures the qualitative experience • Brightness-intensity • Additive color-combining wavelengths • Subtractive color • Saturation-purity+vividness

  13. Visual Systems -Colorblindness • Sex linked • Connected to X

  14. Color Blind Test • http://colorvisiontesting.com/online%20test.htm

  15. Visual Systems • Trichromatic Theory (Thomas Young+Hermann von Helmholte) • 3 types of color receptors-blue, red, green

  16. Visual Systems • Opponent-process theory (EwaldHering) • All color experiences come from 3 systems, red v green – blue v yellow - black (no color) v white (all colors)

  17. Visual Systems • Receptive field • Visual area from which a given ganglion cell receives info (selective)

  18. Hearing • Sine waves-1,100 / second • 2 properties • Frequency-measured in hertz (HZ) • # of cycles/time • Amplitude-strength-peak/valley • Pitch-highness or lowness of sound • 20 HZ-20,000 HZ • Piano 88 keys, 30 HZ – 4,000 HZ • Loudness-physical intensity, determined by amplitude • Large amplitude=loud • Small=soft • Decibel levels-measures loudness • Timbre-complexity of sound waves • Pure sound = 1 sound wave

  19. http://www.frontiernet.net/~imaging/play_a_piano.html

  20. http://www.freemosquitoringtones.org/hearing_test/

  21. Physiology • 4 energy transformations • 1)airborne sound waves to fluid waves • 2)fluid waves to mechanical vibrations • 3)vibrations to electrical impulses • 4)impulses to auditory cortex

  22. Physiology • Sound travels • 1)external ear-reflects of pinna through outer ear canal • Hits eardrum (tympanic membrane) • 2)Middle Ear-3 small bones • Hammer, anvil + stirrup (vibrate) • 3)inner ear • Cochlea – primary organ of hearing (fluid filled) • Basilar membrane – inside cochlea • Transform fluid wave to nerve impulses w/ stimulus of hair cells • Auditory nerve • Carries nerve impulses from cochlea to brain • Auditory cortex • In temperal lobe • Receives auditory nerve impulsesAbsolute threshold

  23. Place Theory (George von Bekesy) • Different frequency tones produce maximum activation at different locations along basilar membrane, w/ the result that pitch can be coded by the place that which activation occurs.

  24. Frequency Theory • Tones produce a rate of vibration in the basilar membrane equal to frequency, w/ the result that pitch can be coded by frequency of the neural response. • Volley Principle • When peaks in sound waves come too frequently for a single neuron to fire at each peak, several neurons fire a group at the frequency of the stimulus tone

  25. Other Senses • Smell – Olfactory cilia • 8 molecules to stimulate • 40 nerve endings to smell • Olfactory bulb • Center for smelling • Located just below the frontal lobe of the cortex • Pheromones • Chemicals secreted to signal sexual receptivity, danger, territory + food.

  26. Other Senses • Taste-greatly influenced by smell • Tongue • Papillae-bumpy surface • Four primary nerve endings • Tastes-sweet, sour, bitter, salty • 5thumani MSG (Mono Sodium Glutamate) • Regenerates frequently

  27. Other Senses • Touch • Skin-cutaneous senses (skin’s senses) • Meissner corpuscles • rubbing • Merkel disks • pressure • Erogenous zones • Skin that is especially sensitive • Gives rise to erotic / sexual sensations

  28. Touch cont. • Vestibular / kinesthetic • Helps head position w/ gravity • Inner ear/fluid+hairs • Ex. Motion sickness (reading in car) • Kinesthetic • Constant sensory feedback about what the body is doing during motor activity.

  29. Pain • Body’s response to stimulation from noxious stimuli, threaten or cause tissue damage • 2 types of pain • Nociceptive – negative feeling ex. touch hot stove • Neuropathic-over use, abnormal functioning ex (injury disease) Phantom Limb Phenomenon

  30. Gate-Control Theory • Certain cells in spinal cord act as gates to interrupt and block some pain signals, while sending some to the brain

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