Transcript Olfactory Organs

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
Olfactory Pathway to the Cerebrum
Olfactory
Olfactory Olfactory
epithelium nerve
bulb
fibers (N I)
Olfactory
tract
Central
nervous
system
Cribriform
plate
Superior
nasal
concha
The olfactory organ on
the left side of the nasal
septum
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Figure 17-1b The Olfactory Organs
Basal cell:
divides to replace
To
worn-out olfactory
olfactory
receptor cells
Olfactory bulb
gland
Cribriform
plate
Lamina
propria
Olfactory
nerve fibers
Developing
olfactory
receptor cell
Olfactory
receptor cell
Olfactory
epithelium
Supporting cell
Mucous layer
Knob
Subsance being smelled
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An olfactory receptor is a modified
neuron with multiple cilia extending
from its free surface.
Olfactory cilia:
surfaces contain
receptor proteins
(see Spotlight
Fig. 173)
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
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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
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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/CBI200025989
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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!
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Smell (Olfaction)
• Accessory olfactory system, which detects fluidphase 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
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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.
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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 and
receptors on the
tongue
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Figure 17-3c Gustatory Receptors
Taste
buds
Taste buds
LM  280
Taste bud
LM  650
Nucleus of
transitional cell
Nucleus of
gustatory cell
Nucleus of
basal cell
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) cells
and supporting cells.
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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
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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
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Figure 17-5c The Sectional Anatomy of the Eye
Visual axis
Anterior cavity
Cornea
Posterior Anterior Edge of
pupil
chamber chamber
Iris
Suspensory ligament of lens
Nose
Corneal limbus
Conjunctiva
Lacrimal punctum
Lacrimal caruncle
Lower eyelid
Medial canthus
Ciliary
processes
Lateral
canthus
Lens
Ciliary body
Ora serrata
Sclera
Choroid
Retina
Posterior
cavity
Ethmoidal
labyrinth
Lateral rectus
muscle
Medial rectus
muscle
Optic disc
Fovea
Optic nerve
Orbital fat
Central artery
and vein
Horizontal dissection of right eye
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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
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Figure 17-10 Factors Affecting Focal Distance
Focal distance
Focal distance
Close
source
Light
from
distant
source
(object)
Focal distance
Focal
point
Lens
The closer the light source,
the longer the focal distance
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The rounder the lens,
the shorter the focal distance
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
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Figure 17-11 Accommodation
For Close Vision: Ciliary Muscle Contracted, Lens Rounded
Lens rounded
Focal point
on fovea
Ciliary muscle
contracted
For Distant Vision: Ciliary Muscle Relaxed, Lens Flattened
Lens flattened
Ciliary muscle
relaxed
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The Eye
• Light Refraction of Lens
• http://www.allaboutvision.com/eyeexam/refraction.htm
• Clarity of vision
• “Normal” rating is 20/20
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