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Special Senses

Special Senses. Chapter 17. The Special Senses and their modalities. Olfaction (Smell) - chemical Taste (Gustation) – chemical Vision (Sight) – photo Hearing – mechanical Equilibrium - mechanical. Olfaction. 10 – 100 million receptors on the roof of the nasal cavity. (about 5 square cm)

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Special Senses

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  1. Special Senses Chapter 17

  2. The Special Senses and their modalities • Olfaction (Smell) - chemical • Taste (Gustation) – chemical • Vision (Sight) – photo • Hearing – mechanical • Equilibrium - mechanical

  3. Olfaction • 10 – 100 million receptors on the roof of the nasal cavity. (about 5 square cm) • Three types of cells: • Olfactory receptors (bipolar neurons) • Supporting cells (pseudostratified columnar) • Basal stem cells (mitotic cells producing new receptors) • Just about the only nuerons that replace themselves in mature humans! • Olfactory (Bowman’s) glands – secrete mucus

  4. Olfactory receptors

  5. Olfactory epithelium

  6. 7 primary odors Floral Musky Camphorous Pepperminty Etheraeal Pungent Putrid About 10,000 different odors are recognizable Much depends upon experience and synthetic processing in the brain Dogs have about 30,000 times the acuity for smell Olfactory physiology

  7. Olfactory pathway

  8. Gustation • About 80% of taste is dependent upon smell • 5 primary tastes • Sweet • Salty • Sour • Bitter • Umami (savory) • Lowest threshold is for bitter, highest is for sweet • Lowest adaptation is for bitter, highest for sweet

  9. Taste & the tongue

  10. Four types of Papillae • Circumvallate – at the back of the tongue • Fungiform – all over • Foliate – lateral margins of tongue, taste buds gone after childhood • Filiform – all over tongue but not for taste, for friction

  11. Different receptors respond to different stimuli

  12. Neural pathways • Anterior tongue innervated by the facial nerve (CN VII) • Posterior tongue innervated by the glossopharyngeal (CN IX) • Lead to the solitary nucleus in the medulla and then to the thalamus and gustatory cortex (perception) or limbic system via the hypothalamus

  13. Vision • Accessory structures • Eyelids (palpabrae) • Eyelashes • Eyebrows • Lacrimal apparatus • Extrinsic eye muscles • Superior & inferior rectus • Lateral & medial rectus • Superior & inferior obliques

  14. The eye

  15. Fig. 16.05

  16. The Eyeball

  17. The eyeball

  18. The Tunics of the eye

  19. The iris

  20. Fig. 16.08 The retina

  21. Fig. 16.09 Photoreceptors

  22. Circulation of aqueous humor

  23. The Optics of vision:Refraction

  24. Fig. 16.12 Common vision defects and their correction

  25. Rods & Cones~ 125 million rods ~ 6 million cones

  26. Physiology of photoreception

  27. Physiology of photoreception

  28. Fig. 16.15

  29. Color Sensitivity • Integration of information from red, green, and bluecones Figure 17–16

  30. Color Blindness • Inability to detect certain colors • Normal color vision • 16% blue • 10% green • 74% red • Red-green color-blindness • Missing red cones leads to an inability to distinguish re from green. • Can be variable • Most common form is X-linked, leading to more male than females Figure 17–17

  31. Visual peception and neural pathways

  32. Off-Center Neurons • Inhibited by light in central zone • Stimulated by illumination at edges • Aids in “Acuity” • Cones are for precise vision • Rods are for contrast & low light and peripheral vision Figure 17–18

  33. Visual pathways

  34. Contralateral & ipsilateral paths

  35. The Ear Figure 17–20

  36. Middle Ear Figure 17–21

  37. Inner Ear Figure 17–22

  38. Anterior, Posterior, and Lateral Semicircular Ducts Figure 17–23

  39. Fig. 16.23

  40. Utricle and Saccule Figure 17–23

  41. Otolith • Gelatinous matrix and statoconia Figure 17–24

  42. Peripheral Muscle Tone, Head, and Neck Movements • Instructions descend in vestibulospinal tracts of spinal cord

  43. The Cochlea Figure 17–26

  44. Fig. 16.20d

  45. Fig. 16.21

  46. Sound • Consists of waves of pressure through air or water

  47. Pressure Wave Figure 17–28

  48. Pressure Wave • Consists of region where air molecules are crowded together • Adjacent zone where molecules are farther apart • Sine waves: • S-shaped curves

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