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Chapter 41

Chapter 41. Sensory Reception. Sensory receptors Neuron endings Specialized receptor cells in close contact with neurons Sense organs Sensory receptors Accessory cells. Mechanoreceptors Transduce mechanical energy Animal functions Feeling Hearing Maintaining balance. Chemoreceptors

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Chapter 41

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  1. Chapter 41 Sensory Reception

  2. Sensory receptors • Neuron endings • Specialized receptor cells in close contact with neurons • Sense organs • Sensory receptors • Accessory cells

  3. Mechanoreceptors • Transduce mechanical energy • Animal functions • Feeling • Hearing • Maintaining balance

  4. Chemoreceptors • Transduce certain kinds of chemical compounds • Allow taste and olfaction

  5. Thermoreceptors • Transduce thermal energy • In endothermic animals, thermoreceptors provide cues about body temperature • Some invertebrates use thermoreceptors to locate endothermic prey

  6. Thermoreception

  7. Electroreceptors • Used by predatory fishes to detect prey • Respond to electrical stimuli

  8. Photoreceptors • Transduce light energy • Serve as the sensory receptors in eyespots and eyes

  9. Receptor cells • Absorb energy • Transduce it into electrical energy • Produce receptor potentials • Depolarizations or hyperpolarizations of the membrane • Graded responses

  10. Sensation process • Sensory receptors transmit coded signals • Brain interprets signals

  11. Sensory adaptation • Decrease in frequency of action potentials in a sensory neuron • Occurs even when the stimulus is maintained • Decreases response to the stimulus

  12. Mechanoreceptors • Touch • Pressure • Gravity • Stretch • Movement

  13. Mechanoreceptors are activated when they change shape as a result of being mechanically pushed or pulled

  14. Tactile receptors • Found in the skin • Respond to mechanical displacement of hairs • Respond to displacement of the receptor cells

  15. Nociceptors • Pain receptors • Free nerve endings of certain sensory neurons • Strong tactile stimuli • Temperature extremes • Certain chemicals

  16. Proprioceptors • Enable the animal to perceive orientation of the body and positions of its parts • Muscle spindles • Golgi tendon organs • Joint receptors

  17. Proprioceptors

  18. Statocysts • Gravity receptors • Found in many invertebrates

  19. Statocysts

  20. Vertebrate hair cells • Detect movement • Found in • Lateral line of fishes • Vestibular apparatus • Semicircular canals • Cochlea

  21. Vertebrate hair cells • Single kinocilium • True cilium • Stereocilia • Microvilli • Contain actin filaments

  22. Lateral line organs • Supplement vision in fish and some amphibians • Inform the animal of moving objects or objects in its path

  23. Lateral line organ

  24. Vertebrate inner ear • Labyrinth of fluid-filled chambers • Canals that help maintain equilibrium

  25. Vestibular apparatus • Upper part of the labyrinth • Saccule • Utricle • Semicircular canals

  26. Human ear

  27. Otoliths • Stimulate hair cells that send signals to the brain • Enable the animal to perceive the direction of gravity

  28. Saccule and utricle • Change position when the head is tilted • Change position when the body is moving in a straight line • Semicircular canals • Inform the brain about turning movements

  29. Inner ear

  30. Cristae • Clumps of hair cells • Located within each bulblike enlargement • Stimulated by movements of the endolymph • Fluid that fills each canal

  31. Organ of Corti • Found within the cochlea • Contains auditory receptors

  32. Path taken by sound waves • Sound waves pass through the external auditory canal • Tympanic membrane (eardrum) vibrates • Ear bones transmit and amplify the vibrations through the middle ear

  33. Vibrations pass through the oval window to fluid within the vestibular duct • Pressure waves press on the membranes that separate the three ducts of the cochlea • Bulging of the round window serves as a pressure escape valve

  34. Pressure waves cause movements of the basilar membrane • Movements stimulate the hair cells of the organ of Corti by rubbing them against the overlying tectorial membrane

  35. Neural impulses • Initiated in the dendrites of neurons that lie at the base of each hair cell • Transmitted by the cochlear nerve to the brain

  36. Chemoreceptors for taste and smell • Taste receptor cells • Specialized epithelial cells in taste buds • Olfactory epithelium • Specialized olfactory cells • Axons that extend to the brain

  37. Olfactory epithelium

  38. Taste and smell process • Molecule binds with a receptor • Taste receptor cell • Olfactory receptor cell • Signal transduction process involving a G protein is initiated

  39. Eyespots (ocelli) • Found in cnidarians and flatworms • Detect light • Do not form images

  40. Eyespots

  41. Compound eye of insects and crustaceans • Visual units called ommatidia • Collectively produce a mosaic image • Transparent lens • Crystalline cone • Focuses light onto retinular receptor cells

  42. Human eye structures and functions • Light enters through the cornea • Light is focused by the lens • Image is produced on the retina • Iris regulates the amount of light

  43. Human eye

  44. Photoreceptor cells in the retina • Rods • Function in dim light • Black and white images • Cones • Function in bright light • Color vision

  45. Bipolar cells • Send signals to ganglion cells

  46. Lateral interneurons • Integrate information • Horizontal cells • Receive signals from the rods and cones • Send signals to bipolar cells

  47. Amacrine cells • Receive signals from bipolar cells • Send signals back to bipolar cells and to ganglion cells

  48. Neural pathway in the retina

  49. Human vision process • Light strikes the photopigment rhodopsin in the rod cells • Retinal portion changes shape • Initiates a signal transduction process that involves transducin

  50. G protein activates an esterase that hydrolyzes cGMP • Reduces cGMP concentration • Ion channels close • Membrane becomes hyperpolarized

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