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barbara-snider

CHEMICAL SENSES - PowerPoint PPT Presentation

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CHEMICAL SENSES
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  1. CHEMICAL SENSES • Olfaction • Receptors • Olfactory Pathway • Taste • Basic qualities • Receptors • Taste Pathway • Supertasters

  2. 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

  3. Olfactory Receptors • Chemicals stimulate cilia on olfactory sensory neurons • Located in olfactory mucosa • Cilia contain olfactory receptors • Receptors replaced every 5-7 weeks

  4. Olfactory Receptors • About 350 types of receptors (in humans) • Odorants cause different patterns of responses across receptors (recognition profiles) • Combinatorial code

  5. Olfactory Pathway • Trigeminal Nerve carries information from olfactory receptors • Olfactory bulb: contains glomeruli where OSN fibers have synapses • Amygdala (limbic system)

  6. Olfactory Pathway • Primary Olfactory Cortex (Piriform) - under temporal lobes • Secondary Olfactory Cortex (Orbitofrontal) - frontal lobes near eyes

  7. Taste: Basic Qualities • sweet - sugar hydroxyl • sour - hydrogen ions • salty - sodium ions • bitter - bases • umami (savory) - MSG

  8. Taste Receptors • papillae contain taste buds • taste buds contain taste cells • tips of taste cells are taste pores • receptor sites are located on the taste pores

  9. 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

  10. Taste Pathway • Chorda Tympani Nerve: front and sides of tongue • Glossopharyngeal Nerve: back of tongue • Vagus Nerve: mouth and throat

  11. Taste Pathway • Nucleus of the Solitary Tract (NST) in brain stem • thalamus • frontal lobes: • Insula • Frontal operculum cortex • Orbitofrontal cortex (bimodal taste/smell neurons)

  12. 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