Special senses

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Special senses

  1. 1. Nervous SystemChapter 49 p.1059-1072Special Senses:Vision, Hearing, Smell, Taste
  2. 2. Sensing & Perceiving Sensation: action potential that reaches the brain through sensory neurons Perception: interpretation of the stimuli after the brain is aware of the sensation
  3. 3. Sensory Reception Detection of the energy of a stimulus by sensory cells Sensory receptors: specialized neurons or epithelial cells within a sensory organ
  4. 4. Overview of the nervous systemCentral Nervous System Peripheral Nervous System 1. Sensory input: detection by sensory receptors External senses Brain neurons Internal senses and Spinal Cord neurons Sympathetic interneurons 2. Integration: processing 3. Motor output: Parasympathetic by the CNS response by effector cells
  5. 5. Sensory Receptors detect a specific type of stimulus Exteroreceptors: detect stimuli outside the body Interoreceptors: detect stimuli within the body (visceral senses) http://information4sale.blogspot.ca/2011/09/senses-receptors-rod-and-cone-cells.html
  6. 6. Types of ExteroreceptorsExteroreceptors Stimuli Sensory Organ Photoreceptors Light Eyes Chemoreceptors Chemicals Nose, tongueMechanoreceptors Pressure, movement Skin, muscles, ears Nociceptors Pain SkinThermoreceptors Temperature Skin
  7. 7. Process of Sensory Reception1. Sensory transduction2. Amplification3. Transmission4. Integration
  8. 8. 1. Sensory Transduction Conversion of stimulus energy into a change in the membrane potential of a receptor cell Receptor potential: graded potentials produced in response to a stimuli Examples:  Pressure can stretch the membrane and increase ion flow  Sugar can bind to a receptor that triggers the opening of sodium channels
  9. 9. 2. Amplification Strengthening of stimulus energy that is otherwise too weak to be carried into the nervous system Example:  Sound waves are enhanced 20x by the ear before even reaching the receptors of the inner ear  Photons of light hitting the retina cells triggers an action potential that has 100,000x more energy than the light itself
  10. 10. 3. Transmission Conduction of impulses to the CNS From receptor potentials to action potential:  Intensity of receptor potential equates to frequency of the action potential Sensory receptor can also be the sensory neuron (afferent) or these can be 2 separate cells requiring a synapse
  11. 11. 4. Integration Processing of information Sensory adaptation: a type of integration where there is a decrease in responsiveness with continued stimulation Threshold for transduction varies by sensory cells and with condition
  12. 12. Organization of the PNS Fig. 48.17
  13. 13. 5 Senses4 Special senses with specialized organs: Vision - eyes Hearing - ears Smell - nose Taste - tongue1 Somatic sense Touch - skin
  14. 14. Anatomy of the Eye Iris: regulates the amount of light entering the pupil Cornea & lens: lenses help focus the image on the retina Cornea has the largest body of nerve bundles and is extremely sensitive to pain
  15. 15. Anatomy of the Eye3 tissue layers: Sclera: muscles Choroid: blood vessels Retina: light sensitive cells
  16. 16. Anatomy of the Eye Fovea Centralis or Fovea  Centre of visual field  Shortest distance light has to travel to reach retina  best visual acuity Optic Nerve  Neurons send visual stimuli to the brain
  17. 17. Retina At the back of the eye Consist of 2 types of light-sensitive cells: rods and cones Converts light signal into an electrical signal that is transmitted through the optic nerve to the occipital lobe of the brain
  18. 18. Rod Cells 125 million Light sensitive  can functions in less intense light  responsible for night vision Doesn’t distinguish colour  detects black, white and shades of grey  Explains why night vision is in black & white
  19. 19. Rod Cells Absent in fovea centralis (centre of visual field) Used in peripheral vision Explains why dim star is best seen by looking at it from an angle rather than directly No rods, all cones http://www.positscience.com/media/62/download/fovea.jpg
  20. 20. Cone Cells 6 million Functions best in bright light  requires more light to stimulate Distinguish colours in daylight
  21. 21. Cone Cells Highest density at fovea comprises less than 1% of retinal size but takes up over 50% of the visual cortex in the brain Explains why you achieve the sharpest daylight vision by looking straight at the object of interest http://www.d.umn.edu/~jfitzake/Lectures/DMED/Vision/Retina/Photoreceptors.html
  22. 22. Photoreceptorhttp://www.chm.bris.ac.uk/motm/retinal/conversion.gif
  23. 23. Photoreceptor  Outer segment has a stack of discs  Opsin: membrane protein on discs of photoreceptors  Different for each photoreceptor type  Retinal: light absorbing pigment derived from vitamin Ahttp://www.chm.bris.ac.uk/motm/retinal/conversion.gif
  24. 24. Photoreceptor  Rhodopsin: opsin and retinal complex in rod cells  Photopsin: opsin and retinal complex in cone cellshttp://www.chm.bris.ac.uk/motm/retinal/conversion.gif
  25. 25. Photopsin 3 types based on the 3 primary colours of light  S-cones: short wavelength, blue cones  M-cones: medium wavelength, green cones  L-cones: long wavelength, red cones
  26. 26. Colour Blindness sex-linked genetic disorder deficiency or absence of one or more types of photopsin
  27. 27. Light Transduction in Rod Cells Light “bleaches” rhodopsin  Light changes shape of retinal, detaching it from opsin  Rhodopsin  retinal + opsin  makes rod cells unresponsive  Cones take over In the dark:  Enzyme converts retinal back to original form allowing it to recombine with opsin  Retinal + opsin  rhodopsin
  28. 28. HW Question Explain why you are initially blind to faint light when you walk from a bright environment into a dark place like a movie theatre.
  29. 29. Optic Nerve Light stimulus is transduced by rod/cone cells Transmitted through the optic nerve to the occipital lobe of the brain Interneuron Rod/cone cells occipital lobe (optic nerve)
  30. 30. Sensory Reception: Vision1. Sensory transduction: rod & cone cells2. Amplification: rod & cone cells3. Transmission: optic nerve4. Integration: occipital lobe
  31. 31. Sensory Adaptation in Vision:Afterimage
  32. 32. Sensory Adaptation in Vision:Afterimage Caused when the eyes photoreceptors adapt from overstimulation and lose sensitivity When the eyes are then diverted to a blank space, the adapted photoreceptors send out a weak signal Surrounding cones that were not being excited by that color send out a strong signal
  33. 33. Afterimage
  34. 34. Afterimage Afterimage
  35. 35. Additive Colour Theory Afterimage colour seen is the opposite colour as the original object Primary colours with have an afterimage of their opposing secondary colour and vice versa Primary colours of light:  Red  Green  blue Secondary colours of light:  Cyan  Yellow  magenta
  36. 36. Afterimage Primary green  secondary magenta Primary red  secondary cyan Afterimage
  37. 37. Video: How Brains Learn to SeeHow Brains Learn to See (18:23)TedTV with Pawan Sinhahttp://www.ted.com/talks/lang/eng/pawan_sinha_on_how_brains_learn_to_see.html
  38. 38. Ear Anatomy http://2.bp.blogspot.com/-GNMjU84vRkM/T0JIZeZCESI/AAAAAAAAAZQ/uzwf9O55aUU/s1600/ear.jpg
  39. 39. Video: Human Hearing (2:34)http://www.youtube.com/watch?v=GGqfRvCkt-w&feature=player_embeddedhttp://3.bp.blogspot.com/-R9C_D3tyQmU/T6SUfCJGNpI/AAAAAAAAAIo/KRUpvqTQR9E/s1600/ear-anatomy.jpg
  40. 40. Hearing1. Sound waves hit the ear drum2. Vibration of ear drum vibrate three small bones in middle ear (malleus, incus and stapes) that amplify the sound 22x3. Bones tap on cochlea which is filled with fluid4. Cochlea is lined with ciliated cells that bend in response to vibration5. Movement of cilia signals neurons Interneuron ciliated cells temporal lobe (Cochlear nerve)
  41. 41. Cochlea Anatomy 2 large chambers filled with fluid:  Upper vestibular canal = scala vestibuli  Lower tympanic canal = scala tympani Separated by cochlear duct Organ of Corti on floor of duct scala tympani
  42. 42. Organ of Corti Hair cells: auditory receptor cells Attached to tectorial membrane
  43. 43. Auditory TransductionVideo: Auditory Transduction (6:44)http://www.youtube.com/watch?feature=endscreen&v=PeTriGTENoc&NR=1Video: Organ of Corti Condensed version (3:02) http://www.youtube.com/watch?v=xMUl5CCoW6Y Full version (6:05) http://www.youtube.com/watch?v=1JE8WduJKV4
  44. 44. Auditory Transduction Sound waves translated as pressure move through the cochlea, dissipating at the round window:  vestibular canal  apex  tympanic canal  ascending the cochlea  tip  descending the cochlea Movement vibrates tectorial membrane in organ of corti which bends hair cells Stimulates opening of ion channels and release of neurotransmitters at synapse Sensory (post-synaptic) neurons (cochlear nerve) conducts action potential to temporal lobe of brain
  45. 45. http://wikis.lib.ncsu.edu/images/e/e2/Cochlea_cross_section.jpg
  46. 46. Movement of sound waves through cochlea scala tympanihttp://www.daviddarling.info/encyclopedia/C/cochlea.html http://www.kameraarkasi.org/ses/terminoloji/kulak/cochlea_02.jpg
  47. 47. Auditory Transduction Sound waves translated as pressure move through the cochlea, dissipating at the round window:  vestibular canal  apex  tympanic canal  ascending the cochlea  tip  descending the cochlea Movement vibrates tectorial membrane in organ of corti which bends hair cells Stimulates opening of ion channels and release of neurotransmitters at synapse Sensory (post-synaptic) neurons (cochlear nerve) conducts action potential to temporal lobe of brain
  48. 48. Organ of Corti
  49. 49. Auditory Transduction Sound waves translated as pressure move through the cochlea, dissipating at the round window:  vestibular canal  apex  tympanic canal  ascending the cochlea  tip  descending the cochlea Movement vibrates tectorial membrane in organ of corti which bends hair cells Stimulates opening of ion channels and release of neurotransmitters at synapse Sensory (post-synaptic) neurons (cochlear nerve) conducts action potential to temporal lobe of brain
  50. 50. Organ of Corti
  51. 51. Hearing Volume changes is determined by the amplitude of sound waves which translates into frequency of action potential Pitch is differences in sound wave frequencies which is distinguished by stimulating hair cells in the different parts of the cochlea http://universe-review.ca/I10-85-cochlea2.jpg
  52. 52. Hearing Damage overly loud noises can damage cochlear cilia
  53. 53. Semicircular Canalshttp://3.bp.blogspot.com/-R9C_D3tyQmU/T6SUfCJGNpI/AAAAAAAAAIo/KRUpvqTQR9E/s1600/ear-anatomy.jpg
  54. 54. Stability & Balance Semicircular canals above the cochlea is filled with a gel-like substance containing otoliths Otoliths:  “ear stones”  CaCO3 granules  denser than the gel Hair cells in contact with otoliths  gravity causes otoliths to pull downward on hair cells  direction of bend indicates position to the brain
  55. 55. Stability & BalanceVideo: Ear Balance (1:24)http://www.youtube.com/watch?v=5aHITbGeNT4Video: Balance and the Inner Ear (4:52)Relates back to the cerebellum (brain)http://www.youtube.com/watch?v=mbi6Hyx8kWkVideo: Remote Control Humans (4:02)Galvanic Vestibular Stimulation Interfacehttp://www.youtube.com/watch?v=Kf0E9llkZIU
  56. 56. Brain & MusicBobby McFerrin hacks your brain with music (3:04)http://www.ted.com/talks/bobby_mcferrin_hacks_your_brain_with_music.html In this fun, 3-min performance from the World Science Festival, musician Bobby McFerrin uses the pentatonic scale to reveal one surprising result of the way our brains are wired.Full program from 2009 World Science FestivalNotes and Neurons (105:46)http://worldsciencefestival.com/videos/notes_neurons_in_search_of_the_common_chorus
  57. 57. Smell & Taste Organs: nose & tongueVideo (52:48)The Science of the Senses: Taste and Smell With chef Claudio Aprile (Colborne Lane) CBC: The Nature of Things Originally aired on January 24th, 2008 http://colbornelane.com/video

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