Download Chapter 17, part 1

Anatomy & Physiology
SIXTH EDITION
Chapter 17, part 1
The Special Senses
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Frederic H. Martini
Fundamentals of
Learning Objectives
• Describe the sensory organs of smell, and trace
the olfactory pathways to their destination in the
brain.
• Identify the accessory and internal structures of
the eye, and explain their function.
• Explain how light stimulates the production of
nerve impulses, and trace the visual pathways to
their destination in the brain.
• Describe the structures of the external and middle
ear and explain how they function.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Learning Objectives
• Describe the parts of the inner ear and their roles
in equilibrium and hearing.
• Trace the pathways for the sensations of
equilibrium and hearing to their destinations in
the brain.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
SECTION 17-1
Olfaction
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Olfactory organs
• Contain olfactory epithelium with olfactory
receptors, supporting cells, basal cells
• Olfactory receptors are modified neurons
• Surfaces are coated with secretions from olfactory
glands
• Olfactory reception involved detecting dissolved
chemicals as they interact with odorant binding
proteins
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Figure 17.1 The Olfactory Organs
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Figure 17.1a, b
Olfaction
• Olfactory pathways
• No synapse in the thalamus for arriving
information
• Olfactory discrimination
• Can distinguish thousands of chemical stimuli
• CNS interprets smells by pattern of receptor
activity
• Olfactory receptor population shows
considerable turnover
• Number of receptors declines with age
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SECTION 17-2
Gustation
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Taste receptors
• Clustered in taste buds
• Associated with lingual papillae
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Taste buds
• Contain basal cells which appear to be stem cells
• Gustatory cells extend taste hairs through a
narrow taste pore
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Figure 17.2 Gustatory Reception
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Figure 17.2
Gustatory pathways
• Taste buds are monitored by cranial nerves
• Synapse within the solitary nucleus of the
medulla oblongata
• Then on to the thalamus and the primary
sensory cortex
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Gustatory discrimination
• Primary taste sensations
• Sweet, sour, salty, bitter
• Receptors also exist for umami and water
• Taste sensitivity shows significant individual
differences, some of which are inherited
• The number of taste buds declines with age
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SECTION 17-3
Vision
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Accessory structures of the eye
• Eyelids (palpebrae) separated by the
palpebral fissue
• Eyelashes
• Tarsal glands
• Lacrimal apparatus
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 17.3 Eternal Features and Accessory
Structures of the Eye
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Figure 17.3a, b
external structures of the eye
• Conjunctiva covers most of eye
• Cornea is transparent anterior portion
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Lacrimal apparatus
• Secretions from the lacrimal gland contain
lysozyme
• Tears form in the lacrimal glands, wash across
the eye and collect in the lacrimal lake
• Pass through the lacrimal punctae, lacrimal
canaliculi, lacrimal sac and nasolacrimal duct
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The eye
• Three layers
• Outer fibrous tunic
• Sclera, cornea, limbus
• Middle vascular tunic
• Iris, ciliary body, choroid
• Inner nervous tunic
• Retina
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Figure 17.4 The Sectional Anatomy of the Eye
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Figure 17.4a, b
internal structures of the eye
• Ciliary body
• Ciliary muscles and ciliary processes, which
attach to suspensory ligaments of lens
• Retina
• Outer pigmented portion
• Inner neural part
• Rods and cones
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Figure 17.4 The Sectional Anatomy of the Eye
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Figure 17.4c
Figure 17.5 The Pupillary Muscles
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Figure 17.5
retina
• Retina contains rods and cones
• Cones densely packed at fovea (center of the
macula lutea)
• Retinal pathway
• Photoreceptors to bipolar cells to ganglion
cells, to the brain via the optic nerve
• Axons of ganglion cells converge at blind
spot (optic disc)
• Horizontal cells and amacrine cells modify the
signal passed along the retinal neurons
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Figure 17.6 The Organization of the Retina
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Figure 17.6a