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17-1 Smell (Olfaction)
• Olfactory Organs
• Provide sense of smell
• Located in nasal cavity on either side of nasal
septum
• Made up of two layers
1. Olfactory epithelium
2. Lamina propria
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Figure 17-1a The Olfactory Organs
Olfactoryepithelium
Olfactory Pathway to the Cerebrum
Olfactorynervefibers (N I)
Olfactorybulb
Olfactorytract
Centralnervoussystem
Superiornasal
concha
Cribriformplate
The olfactory organ onthe left side of the nasal septum
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Figure 17-1b The Olfactory Organs
Olfactoryepithelium
Cribriformplate
Laminapropria
Basal cell:divides to replaceworn-out olfactory
receptor cells Olfactorygland
Toolfactory
bulb
Olfactorynerve fibers
Developingolfactoryreceptor cell
Olfactoryreceptor cell
Supporting cell
Mucous layer
Knob
Olfactory cilia:surfaces containreceptor proteins(see SpotlightFig. 173)
Subsance being smelled
An olfactory receptor is a modifiedneuron with multiple cilia extendingfrom its free surface.
© 2012 Pearson Education, Inc.
17-1 Smell (Olfaction)
• Olfactory Pathways
• Axons leaving olfactory epithelium
• Collect into 20 or more bundles
• Penetrate cribriform plate of ethmoid
• Reach olfactory bulbs of cerebrum where first
synapse occurs
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17-1 Smell (Olfaction)
• Olfactory Pathways
• Axons leaving olfactory bulb:
• Travel along olfactory tract to reach olfactory cortex,
hypothalamus, and portions of limbic system
• Arriving information reaches information centers
without first synapsing in thalamus
© 2012 Pearson Education, Inc.
17-1 Smell (Olfaction)
• Olfactory Discrimination
• Can distinguish thousands of chemical stimuli
• CNS interprets smells by the pattern of receptor
activity
• Olfactory Receptor Population
• Considerable turnover
• Number of olfactory receptors declines with age
© 2012 Pearson Education, Inc.
Smell (Olfaction)
• Olfactory Discrimination
• Can distinguish thousands of chemical stimuli
• CNS interprets smells by the pattern of receptor
activity
• Odor strength and quality/Smell better in the Fall?
• Number of olfactory receptors declines with age
• http://informahealthcare.com/doi/abs/10.1081/CBI-20
0025989
© 2012 Pearson Education, Inc.
Smell (Olfaction)
• 2000-4000 chemical stimuli
• Odor information is stored in long-term memory and has strong connections to emotional memory
• If your nose is at its best, you can tell the difference between 4000-10,000 smells!
• Dogs have 1 million smell cells per nostril and their smell cells are 100 times larger than humans!
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
© 2012 Pearson Education, Inc.
Smell (Olfaction)
• Accessory olfactory system, which detects fluid-phase stimuli. Behavioral evidence suggests that these fluid-phase stimuli often function as pheromones
• In women, the sense of olfaction is strongest around the time of ovulation
© 2012 Pearson Education, Inc.
Smell (Olfaction)
• Humans can detect individuals that are blood related kin (mothers and children but not husbands and wives) from olfaction. Mothers can identify by body odor their biological children but not their stepchildren. Preadolescent children can olfactory detect their full siblings but not half-siblings or step siblings and this might explain incest avoidance and the Westermarck effect.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
© 2012 Pearson Education, Inc.
17-2 Taste (Gustation)
• Gustation
• Provides information about the foods and liquids
consumed
• Taste Receptors (Gustatory Receptors)
• Are distributed on tongue and portions of pharynx and
larynx
• Clustered into taste buds
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Figure 17-3a Gustatory Receptors
Water receptors(pharynx) Umami
Sour
Bitter
Salty
Sweet
Landmarks andreceptors on thetongue
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Figure 17-3c Gustatory Receptors
Tastebuds
Taste buds
Nucleus oftransitional cell
Nucleus ofgustatory cell
Nucleus ofbasal cell
Taste bud LM 650
LM 280
Transitional cell
Gustatory cell
Basal cell
Taste hairs(microvilli)
Taste pore
Taste buds in a circumvallate papilla.A diagrammatic view of a taste bud,showing gustatory (receptor) cellsand supporting cells.
© 2012 Pearson Education, Inc.
17-2 Taste (Gustation)
• Gustatory Discrimination
• Four primary taste sensations
1. Sweet
2. Salty
3. Sour
4. Bitter
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17-2 Taste (Gustation)
• Additional Human Taste Sensations
• Umami
• Characteristic of beef/chicken broths and Parmesan
cheese
• Receptors sensitive to amino acids, small peptides, and
nucleotides
• Water
• Detected by water receptors in the pharynx
© 2012 Pearson Education, Inc.
17-2 Taste (Gustation)
• Gustatory Discrimination
• Dissolved chemicals contact taste hairs
• Bind to receptor proteins of gustatory cell
• Salt and sour receptors
• Chemically gated ion channels
• Stimulation produces depolarization of cell
• Sweet, bitter, and umami stimuli
• G proteins
• Gustducins
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Supertaster
• A person whose sense of taste is significantly sharper than average. Women are more likely to be supertasters, as are Asians, Africans, and South Americans. Among individuals of European descent, it is estimated that about 25% of the population are supertasters
© 2012 Pearson Education, Inc.
Figure 17-5c The Sectional Anatomy of the Eye
Lacrimal punctum
Nose
Lens
Edge ofpupil
Visual axis
Anterior cavity
Posteriorchamber
Anteriorchamber
Lacrimal caruncle
Medial canthus
Ciliaryprocesses
Ciliary body
Ora serrata
Ethmoidallabyrinth
Medial rectusmuscle
Optic disc
Optic nerve
Central arteryand vein
Horizontal dissection of right eye
Orbital fat
Fovea
Lateral rectusmuscle
Posteriorcavity
Retina
Choroid
Sclera
Lateralcanthus
Lower eyelid
Conjunctiva
Corneal limbus
Suspensory ligament of lens
Iris
Cornea
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17-3 The Eye
• Light Refraction
• Bending of light by cornea and lens
• Focal point
• Specific point of intersection on retina
• Focal distance
• Distance between center of lens and focal point
© 2012 Pearson Education, Inc.
Figure 17-10 Factors Affecting Focal Distance
Focal distance
Lightfrom
distantsource(object)
Closesource
The closer the light source,the longer the focal distance
Focal distance
Focalpoint
Lens
The rounder the lens,the shorter the focal distance
Focal distance
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17-3 The Eye
• Light Refraction of Lens
• Accommodation
• Shape of lens changes to focus image on retina
• Astigmatism
• Condition where light passing through cornea and
lens is not refracted properly
• Visual image is distorted
© 2012 Pearson Education, Inc.
Figure 17-11 Accommodation
For Close Vision: Ciliary Muscle Contracted, Lens Rounded
Lens rounded
Ciliary musclecontracted
Focal pointon fovea
Lens flattened
Ciliary musclerelaxed
For Distant Vision: Ciliary Muscle Relaxed, Lens Flattened
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