1. The Special Senses—Smell
Olfactory Organs
Olfactory epithelium
Olfactory receptor cells
Neurons sensitive to odorants
Supporting cells
Basal (stem) cells
Olfactory glands
Mucus-secreting cells
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2. The Special Senses—Smell
The Olfactory Organs
Figure 9-6(a)

3. The Special Senses—Smell
The Olfactory Organs
Figure 9-6(b)

4. The Special Senses—Taste
Taste (Gustatory) Receptors
Taste buds
Found within papillae on tongue, pharynx, larynx
Contain gustatory cells, supportive cells
Taste hairs (cilia) extend into taste pores
Sense salt, sweet, sour, bitter
Also sense umami, water
Synapse in medulla oblongata
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5. The Special Senses—Taste
Gustatory Receptors
Figure 9-7(a)

6. The Special Senses—Taste
Gustatory Receptors
Figure 9-7(b)

7. The Special Senses Key Note
Olfactory information is routed directly to the cerebrum, and olfactory stimuli have powerful effects on mood and behavior. Gustatory sensations are strongest and clearest when integrated with olfactory sensations.
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8. The Special Senses—Vision
Accessory Structures of the Eye
Eyelids (palpebra) and glands
Superficial epithelium of eye
Conjunctiva
Lacrimal apparatus
Tear production and removal
Extrinsic eye muscles
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9. The Special Senses—Vision
The Lacrimal Apparatus
Lacrimal gland produce tears
Bathe conjunctiva
Contain lysozyme to attack bacteria
Tears drain into nasal cavity
Pass through lacrimal canals, lacrimal sac, nasolacrimal duct
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10. The Special Senses—Vision
The Accessory Structures of the Eye
Figure 9-8(a)

11. The Special Senses—Vision
The Accessory Structures of the Eye
Figure 9-8(b)

12. The Special Senses—Vision
Extrinsic Eye Muscles
Move the eye
Six muscles cooperate to control gaze
Superior and inferior rectus
Lateral and medial rectus
Superior and inferior oblique
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13. The Special Senses—Vision
The Extrinsic Eye Muscles
Figure 9-9(a)

14. The Special Senses—Vision
The Extrinsic Eye Muscles
Figure 9-9(b)

15. The Special Senses—Vision
Layers of the Eye
Fibrous tunic
Outermost layer
Vascular tunic
Intermediate layer
Neural tunic
Innermost layer
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16. The Special Senses—Vision
The Sectional Anatomy of the Eye
Figure 9-10(a)

17. The Special Senses—Vision
The Sectional Anatomy of the Eye
Figure 9-10(b)

18. The Special Senses—Vision
The Sectional Anatomy of the Eye
Figure 9-10 (c)

19. The Special Senses—Vision
Layers of the Eye
Fibrous tunic
Sclera
Dense fibrous connective tissue
“White of the eye”
Cornea
Transparent
Light entrance
The Eye: Light Path
PLAY
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20. The Special Senses—Vision
Layers of the Eye
Vascular tunic
Iris
Boundary between anterior and posterior chambers
Ciliary body
Ciliary muscle and ciliary process
Attachment of suspensory ligaments
Choroid
Highly vascular
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21. The Special Senses—Vision
Functions of the Vascular Tunic
Provide a route for blood vessels
Control amount of light entering eye
Adjust diameter of pupil
Secrete and absorb aqueous humor
Adjust lens shape for focusing
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22. The Special Senses—Vision
The Pupillary Muscles
Figure 9-11

23. The Special Senses—Vision
Layers of the Eye
Neural tunic (Retina)
Outer pigmented part
Absorbs stray light
Inner neural part
Detects light
Processes image
Communicates with brain
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24. The Special Senses—Vision
Retinal Organization
Figure 9-12(b)

25. The Special Senses—Vision
Retinal Organization
Figure 9-12(c)

26. The Special Senses—Vision
The Aqueous Humor
Secreted by ciliary processes into posterior chamber
Flows into anterior chamber
Maintains eye shape
Carries nutrients and wastes
Reabsorbed into circulation
Leaves at canal of Schlemm
Excess humor leads to glaucoma
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27. The Special Senses—Vision
Eye Chambers and the Circulation of Aqueous Humor
Figure 9-14

28. The Special Senses—Vision
The Lens
Supported by suspensory ligaments
Built from transparent cells
Surrounded by elastic capsule
Lens and cornea focus light on retina
Bend light (refraction)
Accommodation changes lens shape
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

29. The Special Senses—Vision
Image Formation
Figure 9-16(a)

30. The Special Senses—Vision
Image Formation
Figure 9-16(b)

31. The Special Senses—Vision
Key Note
Light passes through the cornea, crosses the anterior cavity to the lens, transits the lens, crosses the posterior chamber, and then penetrates the retina to stimulate the photoreceptors. Cones, most abundant at the fovea and macula lutea, provide detailed color vision in bright light. Rods, dominant in the peripheral retina, provide coarse color-free vision in dim light.
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32. The Special Senses—Vision
Visual Physiology
Photoreceptors—Cells specialized to respond to photons, packets of light energy
Two types of photoreceptors
Rods
Highly sensitive, non-color vision
In peripheral retina
Cones
Less sensitive, color vision
Mostly in fovea, center of macula lutea
Site of sharpest vision
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33. The Special Senses—Vision
The Structure of Rods and Cones
Figure 9-19

34. The Special Senses—Vision
The Visual Pathway
Figure 9-21

35. Equilibrium and Hearing
Sensory Functions of the Inner Ear
Dynamic equilibrium
Static equilibrium
Hearing
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36. Equilibrium and Hearing
Overview of the Ear
Chambers, canals filled with fluid endolymph
Bony labyrinth
Surrounds membranous labyrinth
Surrounded by fluid perilymph
Consists of vestibule, semicircular canals, cochlea
External, middle ear feed sound to cochlea
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

37. Equilibrium and Hearing
Anatomy of the Ear
External ear
Pinna (auricle)
External acoustic canal
Tympanic membrane (eardrum)
Middle ear
Auditory ossicles
Connect tympanic membrane to inner ear
Auditory tube
Connection to nasopharynx
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38. Equilibrium and Hearing
Anatomy of the Inner Ear
Vestibule
Membranous sacs
Utricle
Saccule
Receptors for linear acceleration, gravity
Semicircular canal with ducts
Receptors for rotation
Cochlea with cochlear duct
Receptors for sound
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39. Equilibrium and Hearing
Receptors of the Inner Ear
Hair cells
Mechanoreceptors
Stereocilia on cell surface
Bending excites/inhibits hair cell
Information on direction and strength of mechanical stimuli
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40. Equilibrium and Hearing
The Anatomy of the Ear
Figure 9-22

41. Equilibrium and Hearing
The Structure of the Middle Ear
Figure 9-23

42. Equilibrium and Hearing
The Anatomy of the Ear
Figure 9-24(a,b)

43. Equilibrium and Hearing
The Vestibular Complex
Figure 9-25(a-c)

44. Equilibrium and Hearing
The Vestibular Complex
Figure 9-25(a, d)

45. Head in horizontal position
Gravity
Figure 9-25(e)
2 of 4
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46. Head in horizontal position
Gravity
Head tilted posteriorly
Gravity
Otolith
moves
“downhill,”
distorting
hair cell
processes
Figure 9-25(e)
3 of 4
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47. The Ear: Balance Head in horizontal position Head tilted posteriorly
Gravity
Head tilted posteriorly
Gravity
Otolith
moves
“downhill,”
distorting
hair cell
processes
Receptor
output increases
The Ear: Balance
PLAY
Figure 9-25(e)
4 of 4
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48. Equilibrium and Hearing
Overview of Hearing
Sound waves vibrate tympanic membrane
Ossicles transfer vibration to oval window
Oval window presses on perilymph in vestibular duct
Pressure wave distorts basilar membrane
Hair cells of organ of Corti press on tectorial membrane
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49. Equilibrium and Hearing
The Cochlea and the Organ of Corti
Figure 9-26(a)

50. Equilibrium and Hearing
The Cochlea and the Organ of Corti
Figure 9-26(b)

51. External acoustic canal Cochlear branch of cranial nerve VIII Incus
Oval
window
Malleus
Stapes
Vestibular duct
(perilymph)
Movement
of sound
waves
Vestibular membrane
Cochlear duct
(endolymph)
Basilar membrane
Tympanic duct
(perilymph)
Tympanic
membrane
Round
window
Sound waves arrive at tympanic membrane.
Movement of tympanic membrane causes displacement of the auditory ossicles.
Movement of the stapes at the oval window establishes pressure waves in the perilymph of the vestibular duct.
The pressure waves distort the basilar membrane on their way to the round window of the tympanic duct.
Vibrations of the basilar membrane causes vibration of hair cells against the tectorial membrane.
Information about the region and the intensity of stimulation is relayed to the CNS over the cochlear branch of cranial nerve VIII.
Figure 9-27
1 of 7
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52. External acoustic canal Movement of sound waves Tympanic membrane
Sound waves arrive at tympanic membrane.
Figure 9-27
2 of 7
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53. External acoustic canal Incus Malleus Stapes Movement of sound waves
Tympanic
membrane
Sound waves arrive at tympanic membrane.
Movement of tympanic membrane causes displacement of the auditory ossicles.
Figure 9-27
3 of 7
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54. External acoustic canal Incus Oval window Malleus Stapes Movement
of sound
waves
Tympanic
membrane
Sound waves arrive at tympanic membrane.
Movement of tympanic membrane causes displacement of the auditory ossicles.
Movement of the stapes at the oval window establishes pressure waves in the perilymph of the vestibular duct.
Figure 9-27
4 of 7
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

55. External acoustic canal Incus Oval window Malleus Stapes Movement
of sound
waves
Tympanic
membrane
Round
window
Sound waves arrive at tympanic membrane.
Movement of tympanic membrane causes displacement of the auditory ossicles.
Movement of the stapes at the oval window establishes pressure waves in the perilymph of the vestibular duct.
The pressure waves distort the basilar membrane on their way to the round window of the tympanic duct.
Figure 9-27
5 of 7
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

56. External acoustic canal Incus Oval window Malleus Stapes
Vestibular duct
(perilymph)
Movement
of sound
waves
Vestibular membrane
Cochlear duct
(endolymph)
Basilar membrane
Tympanic duct
(perilymph)
Tympanic
membrane
Round
window
Sound waves arrive at tympanic membrane.
Movement of tympanic membrane causes displacement of the auditory ossicles.
Movement of the stapes at the oval window establishes pressure waves in the perilymph of the vestibular duct.
The pressure waves distort the basilar membrane on their way to the round window of the tympanic duct.
Vibrations of the basilar membrane causes vibration of hair cells against the tectorial membrane.
Figure 9-27
6 of 7
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57. The Ear: Receptor Complexes
External
acoustic
canal
Cochlear branch of
cranial nerve VIII
Incus
Oval
window
Malleus
Stapes
Vestibular duct
(perilymph)
Movement
of sound
waves
Vestibular membrane
Cochlear duct
(endolymph)
Basilar membrane
Tympanic duct
(perilymph)
Tympanic
membrane
Round
window
Sound waves arrive at tympanic membrane.
Movement of tympanic membrane causes displacement of the auditory ossicles.
Movement of the stapes at the oval window establishes pressure waves in the perilymph of the vestibular duct.
The pressure waves distort the basilar membrane on their way to the round window of the tympanic duct.
Vibrations of the basilar membrane causes vibration of hair cells against the tectorial membrane.
Information about the region and the intensity of stimulation is relayed to the CNS over the cochlear branch of cranial nerve VIII.
The Ear: Receptor Complexes
PLAY
Figure 9-27
7 of 7
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58. Equilibrium and Hearing
Auditory Pathways
Hair cells excite sensory neurons
Sensory neurons located in spiral ganglion
Afferent axons form cochlear branch of vestibulocochlear nerve (CN VIII)
Synapses in cochlear nucleus in medulla
Neurons relay to midbrain
Midbrain relays to thalamus
Thalamus relays to auditory cortex (temporal lobe) in a frequency map
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59. Equilibrium and Hearing
Pathways for Auditory Sensations
Figure 9-28

60. Equilibrium and Hearing
Key Note
Balance and hearing both rely on hair cells. Which stimulus excites a particular group depends on the structure of the associated sense organ. In the semicircular ducts, fluid movement due to head rotation is sensed. In the utricle and saccule, shifts in the position of otoliths by gravity is sensed. In the cochlea, sound pressure waves distort the basilar membrane.
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61. Aging and the Senses Impact of Aging on Sensory Ability
Gradual reduction in smell and taste sensitivity as receptors are lost
Lens changes lead to presbyopia (loss of near vision)
Chance of cataract increases
Progressive loss of hearing sensitivity as receptors are lost (presbycusis)
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings