Special Senses

1
Special Senses

• Chapter 16

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 (Bowmans) glands secrete mucus

4
Olfactory receptors
Fig.16.01
5
Olfactory physiology

• 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

6
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

7
Taste the tongue
Fig.16.02
8
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

9
Different receptors respond to different stimuli
10
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

11
Vision

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

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Fig. 16.04
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Fig. 16.05
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The Eyeball
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Fig. 16.06
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Fig. 16.07
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The retina
Fig. 16.08
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Photoreceptors
Fig. 16.09
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Fig. 16.10
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The Optics of visionRefraction
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Common vision defects and their correction
Fig. 16.12
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Fig. 16.13
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Fig. 16.14
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Fig. 16.15
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Fig. 16.16a,b
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Fig. 16.16c, d
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Fig. 16.17
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Fig. 16.18
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Fig. 16.19
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Fig. 16.20a
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Fig. 16.20b
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Fig. 16.20c
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Fig. 16.20d
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Fig. 16.21
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Fig. 16.22
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Fig. 16.23
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Fig. 16.24
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Fig. 16.25
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Fig. 16T01a
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Fig. 16T01b
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Fig. 16T01c
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Fig. 16T01d
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Fig. 16T01e
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Fig. 16T01f
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Fig. 16T02a
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Fig. 16T02b
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Fig. 16T02c