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Gustation and Olfaction (Taste and Smell)

Gustation and Olfaction (Taste and Smell). chemoreceptors chemical substance dissolved in mucus G-protein-linked receptors all smell some taste sweet bitter umami (e.g., glutamate) channel-linked receptors some taste sour salt. Rhoades and Pflanzer, Human Physiology

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Gustation and Olfaction (Taste and Smell)

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  1. Gustation and Olfaction(Taste and Smell) • chemoreceptors • chemical substance dissolved in mucus • G-protein-linked receptors • all smell • some taste • sweet • bitter • umami (e.g., glutamate) • channel-linked receptors • some taste • sour • salt Rhoades and Pflanzer, Human Physiology cf. Fig. 10-6 Ganong

  2. gustatory cells located in taste buds of the tongue also of the pharynx, epiglottis and soft palate about 50 - 100 per bud hairs are microvilli Taste Fig. 16.6

  3. Taste • 5 (or 6) Taste Modalities received from all parts of the tongue • sour • H+ • salt • ions, especially Na+ & Cl- • sweet • various organic substances • sucrose • phenylalanine • Pb • bitter • various organic substances • alkaloids • many drugs • umami / savory: a fifth taste • glutamate • fat: a sixth taste? • long chain fatty acids (via the CD36 receptor) J. Clin. Invest.115:3177-3184 (2005)

  4. Neural Pathways • Neural pathways • facial (VII) and glossopharyngeal (IX) nerves  • medulla and thalamus  • parietal lobe and insula Ganong, 20th edition Fig. 10-5 Ganong

  5. Smell • Olfactory cells are bipolar neurons • axons form olfactory nerve • cribriform plate of ethmoid bone • roof of nasal cavity • floor of skull Fig. 16.7

  6. Smell • Sniffing increases air flow to roof of nasal cavity. • able to distinguish between thousands of different smells • total number of smell modalities not known • Different smells produce different patterns of stimulation on different populations of olfactory receptors. • Smell contributes significantly to the “taste” of food.

  7. olfactory nerves (sensory)  olfactory tract (mixed)  temporal lobe portions of limbic system thalamic relay NOT required Smells can rapidly trigger emotional responses. pheromones a chemical released by one animal that produces an emotional/behavioral response in another animal probably exist in humans may work via olfactory system Olfactory Pathway Fig. 16.8

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