Transcript No Slide Title

CHEMICAL SENSES
• Olfaction
– Receptors
– Olfactory Pathway
• Taste
– Basic qualities
– Receptors
– Taste Pathway
– Supertasters
Chemical Senses
• Smell and taste detect chemicals that come
into contact with receptors
• Chemical senses act as “gatekeepers,”
determining which things the body should
consume
Olfactory Receptors
• Chemicals stimulate cilia on olfactory sensory
neurons
• Located in olfactory mucosa
• Cilia contain olfactory receptors
• Receptors replaced every 5-7 weeks
Olfactory Receptors
• About 350 types of receptors (in humans)
• Odorants cause different patterns of
responses across receptors (recognition
profiles)
• Combinatorial code
Olfactory Pathway
• Trigeminal Nerve carries information from
olfactory receptors
• Olfactory bulb: contains glomeruli where OSN
fibers have synapses
• Amygdala (limbic system)
Olfactory Pathway
• Primary Olfactory Cortex (Piriform) - under
temporal lobes
• Secondary Olfactory Cortex (Orbitofrontal) frontal lobes near eyes
Taste: Basic Qualities
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sweet - sugar hydroxyl
sour - hydrogen ions
salty - sodium ions
bitter - bases
umami (savory) - MSG
Taste Receptors
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papillae contain taste buds
taste buds contain taste cells
tips of taste cells are taste pores
receptor sites are located on the taste pores
Taste Receptors
• areas on the tongue are sensitive to all 5
qualities, but areas differ in sensitivity
• center of the tongue has no taste receptors
• taste receptors are also located in the mouth
and throat
• receptors replaced every 10 days
Taste Pathway
• Chorda Tympani Nerve: front and sides of
tongue
• Glossopharyngeal Nerve: back of tongue
• Vagus Nerve: mouth and throat
Taste Pathway
• Nucleus of the Solitary Tract (NST) in brain
stem
• thalamus
• frontal lobes:
– Insula
– Frontal operculum cortex
– Orbitofrontal cortex (bimodal taste/smell
neurons)
Supertasters
• Sensitivity to the bitter taste of PROP is
genetically based
• Supertasters are especially sensitive
• Higher density of taste buds
• Lower threshold for bitterness
• Differences in types of taste receptors