Smell

2. Olfactory nerve Olfactory bulb Receptor cells in olfactory membrane Nasal passage Smell

3. Fig. 5.25 Receptors for the sense of smell (olfaction). Olfactory nerve fibers respond to gaseous molecules. Receptor cells are shown in cross section at the left of part (a). (c) On the right, an extreme close-up of an olfactory receptor cell shows the fibers that project into the airflow inside the nose. Receptor proteins on the surface of the fibers are sensitive to different airborne molecules. © Richard Costano, Discover Magazine, 1993

6. Smell and Taste • Olfaction: Sense of smell • Anosmia: Defective sense of smell for a single odor • Taste Buds: Taste-receptor cells • Gustation: Sense of taste • Four Taste Sensations: sweet, salt, sour, bitter • Most sensitive to bitter, least sensitive to sweet • Umami: Possible fifth taste sensation; brothy taste

7. Fig. 5.26 Receptors for taste: (a) Most taste buds are found around the edges of the tongue. Stimulation of the central part of the tongue causes no taste sensations. Receptors for the four primary taste sensations can be found in all of the shaded areas, as well as under the tongue. That is, all taste sensations occur anywhere that taste buds are found. Textbooks that show specific “taste zones” for sweet, salt, sour, and bitter are in error. (b) Detail of a taste bud within the tongue. The buds also occur in other parts of the digestive system, such as the lining of the mouth. Table of Contents Exit

8. Number of correct answers Women and young adults have best sense of smell 4 Women 3 Men 2 0 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80-89 90-99 Age Group Age, Sex and Sense of Smell