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The Senses

The Senses. Super Snout In The News. Sensory Receptors. Changes environmental stimuli into nerve impulses. Generalized Sensory Pathway. Impulses are conducted to sensory areas of the cerebral cortex. Sensing the Internal Environment. Neurons send messages to homeostasis centers in the brain

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The Senses

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  1. The Senses

  2. Super SnoutIn The News

  3. Sensory Receptors • Changes environmental stimuli into nerve impulses

  4. Generalized Sensory Pathway

  5. Impulses are conducted to sensory areas of the cerebral cortex

  6. Sensing the Internal Environment • Neurons send messages to homeostasis centers in the brain • Sensor types • Temperature • Carbon dioxide levels • Oxygen levels • pH • Stretch • Pain

  7. Proprioceptors • Position receptors • Within skeletal muscle • Within tendons • In the inner ear • Sense position in space • Example: stretch receptor in muscle

  8. Mechanoreceptors • Detect touch, movement & pressure • Example: lateral line system

  9. Touch Receptors in Human Skin • Merkel’s discs, Meissner’s corpuscles & Pacinian corpuscles

  10. Thermoreceptors • Sensitive to temperature change

  11. Detecting Infrared • Heat is sensed as infrared radiation • Pit organs of some snakes

  12. Detecting UV light • Insects have receptors to detect UV • UV light transmitted by flowers • Insects are pollinators of flowers Normal Light UV Light

  13. Electroreceptors • Detect electric fields • Found in some fish, salamanders & platypus

  14. Detection of Magnetic Fields • Found in variety of migratory animals • Used for orientation to return to certain areas

  15. Chemoreception • Widespread in animal kingdom • May be found on many parts of the body • Includes senses of taste & smell

  16. Taste • Receptor = taste buds • Detect chemicals in food • Primary tastes • Salty • Sweet • Sour • Bitter

  17. Taste Buds • Within tongue papillae • Microvilli extend through taste pore • Nerves attached to receptor cells

  18. Smell • Olfactory receptors • In nasal epithelium • Can distinguish several thousand odors

  19. Photoreception • Sensing light • Different organisms sense different wavelengths • Not all eyes are image forming

  20. Multifaceted Eyes • Each facet sees part of image • Image is summed by brain to form single image

  21. Phototaxis • Detection of light can change behavior • Positive phototaxis • Organism moves toward light • Negative phototaxis • Organism moves away from light

  22. Human Eye • Camera-like eye also found in cephalopods • Single lens • Receptors sensitive to various wavelengths • Light is focused onto receptors

  23. Structure of the Human Eye

  24. Outer Layer of Eye • Sclera • Tough connective tissue layer • White region of the eye • Cornea • Transparent front of eye • Allows light to enter • Aqueous humor • Liquid behind cornea • Fills anterior chamber

  25. Lens • Just behind aqueous humor • Suspended by ligaments • Ligaments attached to cilliary muscles • Cilliary muscles are able to change lens shape for focusing

  26. Focusing the Eye

  27. Iris • Lies between cornea & lens • Colored part of eye • Controls size of opening • Opening = pupil

  28. Choroid Layer • Dark brown membrane • Lines sclera • Contains blood vessels • Nourishes eye

  29. Retina • Contains sensory receptors • Rods • Low levels of light • Cones • Three types • Stimulated by different wavelengths • Allows for color vision • Fovea • Central area with many cones

  30. Structure of the Retina

  31. Optic Nerve • Creates blind spot in retina • Carries impulses to brain

  32. Depth Perception • Possible because of two eyes in different positions • Provides two images summed by brain • Results in three dimensional quality image

  33. Sound • Type of mechanical energy • Many different types of sound receptors • Some animals hear different wavelengths • Bats use echolocation or animal sonar

  34. Human Hearing • Human ear has three parts • Inner ear has sound receptors

  35. Outer Ear • Pinna • Funnels sound waves • External auditory canal • Leads to tympanic membrane

  36. Tympanic Membrane • Eardrum • Stretches over middle ear opening • Amplifies & increases vibrations • Transfers vibrations to bones of middle ear

  37. Bones of Middle Ear • Malleus, Incus & Stapes • Transfer vibrations to opening of Cochlea

  38. Eustachian Tube • Connects middle ear to nasopharynx • Equalizes air pressure

  39. Inner Ear • Membrane covers oval window • Fluid filled cochlea • Contains organ of Corti • Hair cells are receptors

  40. Transmission of Pressure Waves in Inner Ear

  41. Sound Perception • Different frequencies set up differing wave patterns • Loud sound increases wave magnitude

  42. Vestibule & Semicircular Canals • Detect position and movement • Both found in inner ear

  43. Vestibule • Senses if you are upside down • Detects effects of gravity • Includes two areas • Utricle • Saccule • Jelly filled chambers

  44. Movement Detection in Vestibule • Otoliths – small pebbles • Movement can cause otoliths to stimulate receptor cells • Brain makes sense of sensory input

  45. Semicircular Canals • Three fluid filled canals • Canals oriented at right angles • Contain ciliated sensory cells • Jelly like material lies above cells • Movement initiates depolarization • Complex movements analyzed by brain

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