1. PowerPoint ® Lecture Slide Presentation by Patty Bostwick-Taylor, Florence-Darlington Technical College Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings PART A 8 Special Senses

2. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Senses  General senses of touch  Temperature  Pressure  Pain

3. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Senses  Special senses  Smell  Taste  Sight  Hearing  Equilibrium

4. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Eye and Vision  70% of all sensory receptors are in the eyes  Each eye has over a million nerve fibers  Protection for the eye  Most of the eye is enclosed in a bony orbit  A cushion of fat surrounds most of the eye

5. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye  Eyelids and eyelashes  Conjunctiva  Lacrimal apparatus  Extrinsic eye muscles

6. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye Figure 8.1

7. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye  Eyelids and eyelashes  Tarsal glands lubricate the eye  Ciliary glands are located between the eyelashes

8. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye  Conjunctiva  Membrane that lines the eyelids  Connects to the surface of the eye  Secretes mucus to lubricate the eye

9. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye  Lacrimal apparatus  Lacrimal gland—produces lacrimal fluid  Lacrimal canals—drain lacrimal fluid from eyes  Lacrimal sac—provides passage of lacrimal fluid towards nasal cavity  Nasolacrimal duct—empties lacrimal fluid into the nasal cavity

10. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye Figure 8.2a

11. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye Figure 8.2b

12. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye  Function of the lacrimal apparatus  Protects, moistens, and lubricates the eye  Empties into the nasal cavity

13. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye  Properties of lacrimal fluid  Dilute salt solution (tears)  Contains antibodies and lysozyme

14. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye  Extrinsic eye muscles  Six muscles attach to the outer surface of the eye  Produce eye movements

15. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye Figure 8.3a–b

16. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye Figure 8.3c

17. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye  Layers forming the wall of the eyeball  Fibrous layer  Outside layer  Vascular layer  Middle layer  Sensory layer  Inside layer

18. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye Figure 8.4a

19. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye Figure 8.4b

20. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye: The Fibrous Layer  Sclera  White connective tissue layer  Seen anteriorly as the “white of the eye”  Cornea  Transparent, central anterior portion  Allows for light to pass through  Repairs itself easily  The only human tissue that can be transplanted without fear of rejection

21. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye: Vascular Layer  Choroid is a blood-rich nutritive layer in the posterior of the eye  Pigment prevents light from scattering  Modified anteriorly into two structures  Ciliary body—smooth muscle attached to lens  Iris—regulates amount of light entering eye  Pigmented layer that gives eye color  Pupil—rounded opening in the iris

22. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye: Sensory Layer  Retina contains two layers  Outer pigmented layer  Inner neural layer  Contains receptor cells (photoreceptors)  Rods  Cones

23. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye: Sensory Layer  Signals pass from photoreceptors via a two- neuron chain  Bipolar neurons  Ganglion cells  Signals leave the retina toward the brain through the optic nerve  Optic disc (blind spot) is where the optic nerve leaves the eyeball  Cannot see images focused on the optic disc

24. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye: Sensory Layer Figure 8.5a

25. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye: Sensory Layer Figure 8.5b

26. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye: Sensory Layer  Neurons of the retina and vision  Rods  Most are found towards the edges of the retina  Allow dim light vision and peripheral vision  All perception is in gray tones

27. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye: Sensory Layer  Neurons of the retina and vision  Cones  Allow for detailed color vision  Densest in the center of the retina  Fovea centralis—area of the retina with only cones  No photoreceptor cells are at the optic disc, or blind spot

28. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye: Sensory Layer  Cone sensitivity  Three types of cones  Different cones are sensitive to different wavelengths  Color blindness is the result of the lack of one cone type

29. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Sensitivities of Cones to Different Wavelengths Figure 8.6

30. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Lens  Biconvex crystal-like structure  Held in place by a suspensory ligament attached to the ciliary body

31. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Lens Figure 8.4a

32. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Lens  Cataracts result when the lens becomes hard and opaque with age  Vision becomes hazy and distorted  Eventually causes blindness in affected eye

33. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Lens Figure 8.7

34. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Two Segments, or Chambers, of the Eye  Anterior (aqueous) segment  Anterior to the lens  Contains aqueous humor  Posterior (vitreous) segment  Posterior to the lens  Contains vitreous humor

35. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anterior Segment  Aqueous humor  Watery fluid found between lens and cornea  Similar to blood plasma  Helps maintain intraocular pressure  Provides nutrients for the lens and cornea  Reabsorbed into venous blood through the scleral venous sinus, or canal of Schlemm

36. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Posterior Segment  Vitreous humor  Gel-like substance posterior to the lens  Prevents the eye from collapsing  Helps maintain intraocular pressure

37. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Ophthalmoscope  Instrument used to illuminate the interior of the eyeball  Can detect diabetes, arteriosclerosis, degeneration of the optic nerve and retina

38. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Posterior Wall of Retina as Seen with Ophthalmoscope Figure 8.8

39. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Pathway of Light Through the Eye  Light must be focused to a point on the retina for optimal vision  The eye is set for distance vision (over 20 feet away)  Accommodation—the lens must change shape to focus on closer objects (less than 20 feet away)

40. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Pathway of Light Through the Eye Figure 8.9

41. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Pathway of Light Through the Eye  Image formed on the retina is a real image  Real images are  Reversed from left to right  Upside down  Smaller than the object

42. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Images Formed on the Retina Figure 8.10

43. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Visual Fields and Visual Pathways  Optic chiasma  Location where the optic nerves cross  Fibers from the medial side of each eye cross over to the opposite side of the brain  Optic tracts  Contain fibers from the lateral side of the eye on the same side and the medial side of the opposite eye

44. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 8.11 Visual Fields and Visual Pathways

45. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Eye Reflexes  Internal muscles are controlled by the autonomic nervous system  Bright light causes pupils to constrict through action of radial, circular, and ciliary muscles  Viewing close objects causes accommodation  External muscles control eye movement to follow objects  Viewing close objects causes convergence (eyes moving medially)

46. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings A Closer Look  Emmetropia—eye focuses images correctly on the retina  Myopia (nearsighted)  Distant objects appear blurry  Light from those objects fails to reach the retina and are focused in front of it  Results from an eyeball that is too long

47. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings A Closer Look  Hyperopia (farsighted)  Near objects are blurry while distant objects are clear  Distant objects are focused behind the retina  Results from an eyeball that is too short or from a “lazy lens”

48. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings A Closer Look  Astigmatism  Images are blurry  Results from light focusing as lines, not points, on the retina due to unequal curvatures of the cornea or lens

49. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Homeostatic Imbalances of the Eyes  Night blindness—inhibited rod function that hinders the ability to see at night  Color blindness—genetic conditions that result in the inability to see certain colors  Due to the lack of one type of cone (partial color blindness)  Cataracts—when lens becomes hard and opaque, our vision becomes hazy and distorted

50. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Homeostatic Imbalances of the Eyes  Glaucoma—can cause blindness due to increasing pressure within the eye  Hemianopia—loss of the same side of the visual field of both eyes; results from damage to the visual cortex on one side only

51. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Ear  Houses two senses  Hearing  Equilibrium (balance)  Receptors are mechanoreceptors  Different organs house receptors for each sense

52. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Ear  The ear is divided into three areas  External (outer) ear  Middle ear (tympanic cavity)  Inner ear (bony labyrinth)

53. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Ear Figure 8.12

54. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The External Ear  Involved in hearing only  Structures of the external ear  Auricle (pinna)  External acoustic meatus (auditory canal)  Narrow chamber in the temporal bone  Lined with skin and ceruminous (wax) glands  Ends at the tympanic membrane

55. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Middle Ear (Tympanic Cavity)  Air-filled cavity within the temporal bone  Only involved in the sense of hearing

56. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Middle Ear (Tympanic Cavity)  Two tubes are associated with the inner ear  The opening from the auditory canal is covered by the tympanic membrane  The auditory tube connecting the middle ear with the throat  Allows for equalizing pressure during yawning or swallowing  This tube is otherwise collapsed

57. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Bones of the Middle Ear (Tympanic Cavity)  Three bones (ossicles) span the cavity  Malleus (hammer)  Incus (anvil)  Stapes (stirrip)  Function  Vibrations from eardrum move the malleus  anvil  stirrup  inner ear

58. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Ear Figure 8.12

59. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Inner Ear or Bony Labyrinth  Includes sense organs for hearing and balance  Filled with perilymph  A maze of bony chambers within the temporal bone  Cochlea  Vestibule  Semicircular canals

60. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Ear Figure 8.12

61. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Organs of Equilibrium  Equilibrium receptors of the inner ear are called the vestibular apparatus  Vestibular apparatus has two functional parts  Static equilibrium  Dynamic equilibrium

62. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Organs of Equilibrium Figure 8.14a–b

63. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Static Equilibrium  Maculae—receptors in the vestibule  Report on the position of the head  Send information via the vestibular nerve  Anatomy of the maculae  Hair cells are embedded in the otolithic membrane  Otoliths (tiny stones) float in a gel around the hair cells  Movements cause otoliths to bend the hair cells

64. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure and Function of Maculae Figure 8.13a

65. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure and Function of Maculae Figure 8.13b

66. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Dynamic Equilibrium  Crista ampullaris—receptors in the semicircular canals  Tuft of hair cells  Cupula (gelatinous cap) covers the hair cells

67. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Dynamic Equilibrium Figure 8.14c

68. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Dynamic Equilibrium  Action of angular head movements  The cupula stimulates the hair cells  An impulse is sent via the vestibular nerve to the cerebellum

69. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Organs of Hearing  Organ of Corti  Located within the cochlea  Receptors = hair cells on the basilar membrane  Gel-like tectorial membrane is capable of bending hair cells  Cochlear nerve attached to hair cells transmits nerve impulses to auditory cortex on temporal lobe

70. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Organs of Hearing Figure 8.15a

71. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Organs of Hearing Figure 8.15b

72. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Mechanism of Hearing  Vibrations from sound waves move tectorial membrane  Hair cells are bent by the membrane  An action potential starts in the cochlear nerve  Continued stimulation can lead to adaptation

73. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Mechanism of Hearing Figure 8.16a

74. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Mechanism of Hearing Figure 8.16b–c

75. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Olfaction—The Sense of Smell  Olfactory receptors are in the roof of the nasal cavity  Neurons with long cilia  Chemicals must be dissolved in mucus for detection  Impulses are transmitted via the olfactory nerve  Interpretation of smells is made in the cortex

76. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Olfactory Epithelium Figure 8.17

77. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Sense of Taste  Taste buds house the receptor organs  Location of taste buds  Most are on the tongue  Soft palate  Cheeks

78. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Taste Buds Figure 8.18

79. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Tongue and Taste  The tongue is covered with projections called papillae  Filiform papillae—sharp with no taste buds  Fungifiorm papillae—rounded with taste buds  Circumvallate papillae—large papillae with taste buds  Taste buds are found on the sides of papillae

80. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of Taste Buds  Gustatory cells are the receptors  Have gustatory hairs (long microvilli)  Hairs are stimulated by chemicals dissolved in saliva

81. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of Taste Buds  Impulses are carried to the gustatory complex by several cranial nerves because taste buds are found in different areas  Facial nerve  Glossopharyngeal nerve  Vagus nerve

82. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Taste Sensations  Sweet receptors(sugars)  Saccharine  Some amino acids  Sour receptors  Acids  Bitter receptors  Alkaloids  Salty receptors  Metal ions

83. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Developmental Aspects of the Special Senses  Formed early in embryonic development  Eyes are outgrowths of the brain  All special senses are functional at birth

84. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Senses: Taste and Smell  Both senses use chemoreceptors  Stimulated by chemicals in solution  Taste has four types of receptors  Smell can differentiate a large range of chemicals  Both senses complement each other and respond to many of the same stimuli

85. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Developmental Aspects of the Special Senses  Eye problems  Strabismus—“crossed eyes” results from unequal pulls by the external eye muscles in babies  Ophthalmia neonatorum—conjunctivitis resulting from mother having gonorrhea. Baby’s eyelids are swollen and pus is produced

86. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Developmental Aspects of the Special Senses  Eye problems  Presbyopia—“old vision” results from decreasing lens elasticity that accompanies aging

87. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Developmental Aspects of the Special Senses  Ear problems  Presbycusis—type of sensorineural deafness  Otosclerosis—ear ossicles fuse