Peripheral Nervous System: Afferent Division

1. Peripheral Nervous System: Afferent Division • SENSORY PHYSIOLOGY

2. Chapter Goals After studying this chapter, students should be able to . . . 1. explain how sensory receptors are categorized, give examples of functional categories and explain how tonic and phasic receptors differ. 2. explain the law of specific nerve energies. 3. describe the characteristics of the generator potential. 4. give examples of different types of cutaneous receptors and describe the neural pathways for the cutaneous senses. 5. explain the concepts of receptive fields and lateral inhibition. 6. describe the distribution of taste receptors on the tongue and explain how salty, sour, sweet and bitter tastes are produced. 7. describe the structure and function of the olfactory receptors, and explain how odor discrimination might be accomplished. 8. describe the structure of the vestibular apparatus and explain how it provides information about acceleration of the body in different directions. 9. describe the functions of the outer and middle ear.

3. Chapter Goals 10. describe the structure of the cochlea and explain how movements of the stapes against the oval window result in vibrations of the basilar membrane. 11. explain how mechanical energy is converted into nerve impulses by the organ of Corti and how pitch perception is accomplished. 12. describe the structure of the eye, and how images are brought to a focus on the retina. 13. explain how visual accommodation is achieved and describe the defects associated with myopia, hyperopia, and astigmatism. 14. describe the architecture of the retina, and trace the pathways of light and nerve activity through the retina. 15. describe the function of rhodopsin in the rods and explain dark adaptation is achieved. 16. explain how light affects the electrical activity of rods and their synaptic input to bipolar cells. 17. explain the trichromatic theory of color vision. 18. compare rods and cones with respect to their locations, synaptic connections, and functions.

4. SENSORY PHYSIOLOGY • Sensory Receptors • Pain • Vision • Hearing • Chemical Senses

5. Receptor Physiology 6-3

6. 6-4a

7. 6-4b

8. 6-5

9. 6-6

10. 6-7

11. 6-8a

12. 6-8b

13. 6-9a

14. 6-9b

15. Vision • Structure of Eye (camera analogy) • Vision Problems • Light Receptors • Chemistry • Histology • Fovea • Accommodation

16. 6-10

17. 6-11

18. 6-12

19. 6-13

20. 6-14

21. 6-15

22. 6-16a

23. 6-17

24. 6-18

25. 6-19

26. Accommodation • Pupil accommodation reflex - the smaller the aperture of the pupil, the greater the depth of field. Near objects cause reflex constriction of the pupil. • Changing shape of lens

27. 6-20a

28. 6-20b

29. 6-20c

30. 6-20d

31. Vision Problems • Emmetropia - normal vision • Hypermetropia - far-sightedness (eyeball abnormally flattened) • Myopia - near sightedness (abnormally elongated eyeball) • Astigmatism - irregular refractive surface (corrected with irregularly ground lens. • Presbyopia - vision of old age (loss of lens elasticity)(corrected with bifocals) • Cataracts - opaque lens (corrected with lens replacement)

32. 6-21a

33. 6-21b

34. 6-21c

35. Light Receptors • Rods - sensitive to any visible light • Cones - respond to one of three different wavelengths • i. Dominator cones - all wavelengths • ii. Modulator cones - respond to red, green, or blue (ratio determines color) - Brain can discriminate between 107 different colors. Color blindness = one type of cone missing.

36. 6-22

37. Fovea • Only modulator cones - point where image of focus falls; therefore, if one does not focus directly on an object in dim light, it will be seen more clearly than if focused directly.

38. 6-23

39. 6-24

40. 6-25a

41. 6-25b

42. 6-25c

43. 6-27

44. Analysis of Firing Frequencies Impulses/sec: Red: Green:Blue Ratio Interpretation 50 10 0 5 A shade of red 500 100 0 5 Same, but brighter 10 50 0 0.2 A shade of green

45. 6-28

46. Hearing • Anatomy • Determination of Sound Quality

47. Anatomy 6-33

48. 6-34a

49. 6-34b

50. 6-34c