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Chapter 35

Chapter 35. Senses. Senses. Perceive environment Find food Avoid predators Avoid danger Find shelter Interact socially. Sensory Receptors. Mechanoreceptors Touch, hearing, equilibrium, pressure Thermoreceptors Radiant energy, infrared Nociceptors Pain Chemoreceptors Smell, taste

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Chapter 35

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  1. Chapter 35 Senses

  2. Senses • Perceive environment • Find food • Avoid predators • Avoid danger • Find shelter • Interact socially

  3. Sensory Receptors • Mechanoreceptors • Touch, hearing, equilibrium, pressure • Thermoreceptors • Radiant energy, infrared • Nociceptors • Pain • Chemoreceptors • Smell, taste • Osmoreceptors • Water, solute concentration • Photoreceptors • Light, vision

  4. Sensory Receptors • Sensory receptor • Nerve pathway • Brain integration • Sensory perception

  5. Sensory Receptors • Receptors specific for given stimulus • Strong stimulation • Greater frequency of action potentials • Greater number of neurons • Sensory adaptaion • Frequency of AP decrease or stop w/ constant simulus

  6. Somatic • Start at sensory neurons • Different sensors to different part of brain • Somatosensory cortex

  7. Somatic • Body surface • Free nerve endings • Meissner corpuscles • Pacinian corpuscles • Thermoreceptors • Bulb of Krause • Ruffini endings

  8. Somatic • Muscles • Mechanorecptors • Motion • Position in space • Stretch

  9. Somatic • Pain—perception of injury • Nociceptors • Somatic—skin, skeletal muscle, joints, tendons • Visceral—internal organs • Fewer nocieptors • “Referred” pain • Cell damage releases bradykinins • Bradykinins stimulate nearby nociceptors • Stimulus perceived by brain as pain

  10. Olfaction • Smell • Social communication • Find mates • Find prey • Avoid predators

  11. Olfaction • Well-developed in most mammals • Especially carnivores & ungulates • Non-existent in cetaceans (whales, dolphins, etc.) • Canines 100,000-1 million times better than humans • Bloodhounds 10-100 million times

  12. Olfaction • Poorly developed in most birds • Well-developed in fish • Salmon—ID and return to home streams • Catfish—ID others, maintain social order

  13. Olfaction • Chemicals inhaled • Must be dissolved in liquid (mucus) • Binds to membrane proteins • Triggers depolarization of neurons • Different combinations of receptor activation recognized as patterns by brain

  14. Olfaction

  15. Olfaction • Pheromones • Air-borne chemical that triggers behavioral response in same species • Alarm • Food trail • Sex • Territorial

  16. Taste • Differentiate nutrition vs. noxious • Receptors on various organs • Antennae • Tentacles • Tongue • Legs

  17. Taste • Five tastes in humans • Sweet • Sour • Salty • Bitter • Umami

  18. Chemoreceptors • Antennae • Most arthropods • Multiple functions • Smell & taste most important • Also touch, air motion, vibration, heat • Olfactory receptors bind to odor molecules • Sends signal to antennal lobe in brain

  19. Chemoreceptors • Vomeronasal organ • Many animals (including humans) • Certain smells • Many pheromones • May be involved in triggering some aggression & mating

  20. Chemoreceptors • Vomeronasal organ • Flehmen response • In cat • In deer

  21. Hearing • Detect vibrations • Interpret as sound • Amplitude (loudness) • Frequency (pitch) • Important for communication • Important for finding prey • Important for avoiding predators

  22. Hearing • Sonic—human frequencies • 15 Hz-20,000 Hz • Best at 2,000-4,000 Hz • Ultrasonic—above human frequencies • Bats, dogs • Subsonic—below human frequencies • Snakes (sense through bellies) • Whales, giraffes, elephants (communication)

  23. Hearing • External ear (pinna) • Collects sound • Middle ear • Ossicles • Malleus (hammer) • Incus (anvil) • Stapes (stirrup) • Receive vibrations from tympanum (eardrum) • Transmit to inner ear • Inner ear • Cochlea—auditory nerves • Semicircular canals—balance

  24. Hearing • ,,,

  25. Hearing • Vibrations coming down ear vibrate ossicles • Stapes vibration pushes on oval membrane on cochlea • Fluid in cochlea moves at specific frequency • Fluid wave moves tectorial membrane • Movement of tectorial membrane stimulates nerve impulse

  26. Hearing • ,,,

  27. Hearing • Equilibrium • Vestibular organs (semicircular canals) • Static equilibrium • Linear movement of head • Otolithic membrane movement triggers hairs • Dynamic equilibrium • Rotation, acceleration, deceleration • Fluid bends hairs in cristaampullaris

  28. Hearing • Echolocation • Dolphis, shrews, bats, most whales • Active sonar • Sounds sent out • Hear reflection of sounds (echo) • Able to triangulate sounds

  29. “Hearing” • Lateral line • Detect vibrations in water • Along sides of many fish • Similar to certain aspects of hearing & equilibrium

  30. Vision • Photoreceptors • Part of brain that can interpret pattern of nerve impulses • Pigment molecules absorb incoming photons • Convert photons into action potential

  31. Vision • Invertebrate • Simple • Photosensitive receptors • Do not form images • Light & dark • Ocellus

  32. Vision • Invertebrate • Compound • Arthropods • Multiple facets • Each has own lens & photoreceptor cells • Very sensitive to motion • 360o field of vision • Multiple images integrated in brain • Poor image resolution

  33. Vision • Invertebrate • Mollusks • Many have lens eyes (similar to vertebrates) • Cephalopods have most developed • Hunters, 3 dimensions, often move fast

  34. Vision • Vertebrate • Outer layer • Sclera • Cornea • Middle Layer • Lens • Iris • Pupil • Choroid • Aqueous Humor • Vitreous Humor

  35. Vision • Inner layer • Retina • Macula lutea • Optic disc • TapetumLucidum

  36. Vision • Rods • Low light • Night vision • No color • Cones • Bright light • Day vision • Color

  37. Vision • Accommodation—the process by which an eye changes to keep an object in focus as it moves closer or further away. • Fish, reptiles—Lens moves forwards & backwards in eye • Birds, mammals—ciliary muscles change shape of lens.

  38. Vision • Photons enter through cornea • Are focused by lens • Absorbed by cells in retina • Photon activity stimulates receptors to generate action potential

  39. Vision • Eye placement • Forward-facing • Predators • Depth perception • Side-facing • Prey • Wide field of vision

  40. Other Senses • Electroception • Detect electrical fields • Sharks, skates, rays • Lungfish, coelacanths, sturgeons • Monotremes (especially platypus) • Active—generate own field • Electric eels & fish • Communication • Passive—sense other fields • Chondrichthyes

  41. Other Senses • Magnetoception • Mostly birds • Very important to migration • Some bees • Detect magnetic fields • Magnetite • Found in many rocks & minerals • Source of iron ore • Identified in brains of birds, bees, and humans • When magnetite aligns w/ Earth’s magnetic field, stimulates nerve impulse • Poorly understood sense

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