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Sensory receptors animal systems


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Sensory receptor

Published in: Science

Sensory receptors animal systems

  1. 1. MO Figure Sensory Receptors and the CNS Perennou Nuridsany/Science Source.
  2. 2. Sensory pathways Involve four steps • Sensory reception: sensory receptors detect a stimulus • Sensory transduction: in response to the stimulus, ion channels open or close, which changes the membrane potential • Transmission: an action potential is carried to the CNS • Perception: awareness of the stimulus occurs in the brain.
  3. 3. Figure 1 Sensory reception
  4. 4. Figure 1a
  5. 5. Figure 1b
  6. 6. Figure 2 Amplification Amplification is the process through which a signal is strengthened; often involves signal transduction pathways.
  7. 7. Figure 2a
  8. 8. Figure 2b
  9. 9. Sensory perception Integration: several weak stimuli are added into one large perceived stimulus. Occurs at several steps: • During signal transduction, separate stimuli are added together to generate an action potential. • During transmission, several rapid action potentials are integrated into one. • In the CNS, signals from multiple sensory cells are integrated into one signal.
  10. 10. Sensory adaptation Sensitivity of sensory receptors changes in response to constant stimulation • Enables an animal to adjust to changing environmental conditions. • Enables an animal to ignore constant stimuli that might otherwise be distracting.
  11. 11. Types of sensory receptor • Mechanoreceptors • Chemoreceptors • Electromagnetic receptors • Thermoreceptors • Nociceptors (pain receptors)
  12. 12. Mechanoreceptors • Respond to mechanical stimulation, such as pressure and sound. • Responsible for senses of touch and hearing • Ion channels open or close in response to deformation or movement.
  13. 13. Figure 3 Skin mechanoreceptors Sensory receptors in the skin and surrounding hair follicles respond to pressure.
  14. 14. Figure 4 Lateral line system Used to sense movement of water.
  15. 15. Figure 4a
  16. 16. Figure 4b
  17. 17. Chemoreceptors Bind chemicals, responsible for senses of taste and smell. Olfaction: sense of smell, involves detection of airborne chemicals called odorants. Gustation: sense of taste, involves detection of dissolved chemicals called tastants. Aquatic animals do not have distinct senses of taste and smell.
  18. 18. Figure 5 Pheromones for navigation Lampreys detect pheromones secreted by the larvae of their species to navigate to breeding sites. (a) Jacana/Science Source. (b) Gary Meszaros/Science Source.
  19. 19. Electromechanical receptors • Detect electromagnetic energy such as light, electricity, and magnetism • Photoreceptors detect light and are responsible for vision. Visual organs: Eyespots (planaria): sense light and dark Compound eyes (insects): detect motion. Single-lens eyes (vertebrates and some invertebrates): focus image.
  20. 20. Figure 6 Photoreception Planaria move away from light sources using photosensitive eyespots.
  21. 21. Figure 7 Electromagnetic reception Monarch butterflies use magnetite to orient themselves with respect to Earth’s magnetic field and navigate during winter migrations. Courtesy of Gene Nieminen/USFWS.
  22. 22. Thermoreceptors Sense changes in temperature
  23. 23. Nociceptors (pain receptors) • Detect injurious stimuli such as extreme heat, pressure, and dangerous chemicals. • In humans, many nociceptors are naked dendrites of other types of receptors; thermoreceptors, mechanoreceptors, and chemoreceptors can act as nociceptors.
  24. 24. MO Figure Auditory and Balance System Courtesy of B. Peterson/USFWS.
  25. 25. Figure 1 The Auditory System
  26. 26. Figure 2 The Cochlea Primary site of auditory sense reception. Contains the fluid-filled vestibular and tympanic canals. Vibration of the basilar membrane causes cilia on hair cells to bend. Signals are transmitted to the brain through the auditory nerve.
  27. 27. Figure 2a
  28. 28. Figure 2b
  29. 29. Figure 2c
  30. 30. Figure 3 Hair cells Bend back and forth in response to fluid movements from sound waves. The bending movements are translated into neural signals that are transmitted to the brain. © 2004 Nature Publishing Group Modified from Frolenkov, G. I., et al., Genetic insights into the morphogenesis of inner ear hair cells. Nature Reviews Genetics 5, 489–498 (2004) doi:10.1038/nrg1377. Used with permission.
  31. 31. Figure 4 Mechanism of hearing
  32. 32. Figure 4a
  33. 33. Figure 4b
  34. 34. Figure 4c
  35. 35. Figure 5 Mechanism of hearing The basilar membrane gets thinner and more flexible toward the center of the cochlea.
  36. 36. Figure 5a Mechanism of hearing
  37. 37. Figure 5b Mechanism of hearing The basilar membrane gets thinner and more flexible toward the center of the cochlea.
  38. 38. Figure 6 The balance systems
  39. 39. Figure 6a
  40. 40. Figure 6b
  41. 41. Figure 6c
  42. 42. Figure 7 Semicircular canals © 2007 Nature Publishing Group Sanlaville D. & Verloes, A. CHARGE syndrome: an update. European Journal of Human Genetics 15, 389–399 (2007) doi:10.1038/sj.ejhg.5201778. Used with permission. Clearly visible in normal newborns (left) and missing in CHARGE affected newborns (right).
  43. 43. MO Figure Vision Courtesy of Gary M. Stolz/USFWS.
  44. 44. Figure 1 Eyespots Planaria have primitive eyespots with photosensitive tissue. Eric V. Grave/Science Source.
  45. 45. Figure 2 Compound eyes Thomas Shahan/Science Source. Contain many ommatidia, each with its own lens. Highly sensitive to motion.
  46. 46. Figure 3 Eye and retina anatomy
  47. 47. Figure 3a
  48. 48. Figure 3b
  49. 49. Figure 4 Microscope vs. eyes Both have lenses that refract light. Both can focus an image. Both have an iris that adjusts light levels.
  50. 50. Figure 4a
  51. 51. Figure 4b
  52. 52. Figure 5 Myopia, hyperopia, and astigmatism Abnormal curvature of the lens or cornea results in light focusing incorrectly on the retina.
  53. 53. Figure 5a
  54. 54. Figure 5b
  55. 55. Figure 5c
  56. 56. Figure 6 Retinal neurons Several types of neurons in the retina communicate with each other to refine, sharpen, and process visual stimuli. These include bipolar cells (green), rod photoreceptors (red/purple), cones, amacrine cells, ganglion cells, and others. © 2010 Nature Publishing Group Markus, A. Speedy rod signaling. Nature Neuroscience 13, 410 (2010) doi:10.1038/nn0410-410. Used with permission.
  57. 57. Figure 7 Visual processing Although images are inverted at the retina, the visual cortex of the brain reorients the images properly.
  58. 58. MO Figure Taste and Smell Picture Partners/Science Source.
  59. 59. Figure 1 Chemoreceptors Robert Noonan/Science Source. Insects have olfactory receptors that are typically found on their antennae. Gustatory receptors can be found on mouthparts and legs.
  60. 60. Figure 2 Taste buds Associated with papillae of the tongue. Contain cells that detect sweet, salty, bitter, sour, and umami (savory) tastes.
  61. 61. Figure 2a
  62. 62. Figure 2b
  63. 63. Figure 2c
  64. 64. Figure 3
  65. 65. Figure 4 Olfaction Greg Dimijian/Science Source. Skunks use odorants for defense.
  66. 66. Figure 5 The olfactory pathway Binding of odorants to chemoreceptor neurons triggers action potentials that are transmitted to the olfactory bulb and brain.
  67. 67. Figure 5a
  68. 68. Figure 5b