1. Chemical senses – gustation (taste) and olfaction (smell)
Their chemoreceptors respond to chemicals in aqueous solution
Taste – to substances dissolved in saliva
Smell – to substances dissolved in fluids of the nasal membranes

2. Sense of Smell
The organ of smell is the olfactory epithelium, which covers the superior nasal concha
Olfactory receptor cells are neurons with radiating olfactory cilia
Olfactory receptors are surrounded and cushioned by supporting cells

3. Olfactory Receptors
Figure 15.21

4. Sense of Taste--Taste Buds
Taste is 80% smell
Most of the 10,000 or so taste buds are found on the tongue
Taste buds are found in papillae of the tongue mucosa
2 types of epithelial cells:
Gustatory (taste cells)—gustatory hairs (sensitive)
Basal cells (stem cells for quick replacement days)

5. In order to be tasted, a chemical:
Physiology of Taste
In order to be tasted, a chemical:
Must be dissolved in saliva
Must contact gustatory hairs
Binding of the food chemical:
Depolarizes the taste cell membrane, releasing neurotransmitters
Initiates a generator potential that elicits an action potential

6. Taste Buds
Figure 15.23

7. There are five basic taste sensations
Sweet – sugars, saccharin, alcohol, and some amino acids
Salty – metal ions
Sour – hydrogen ions
Bitter – alkaloids such as quinine and nicotine
Umami- amino acids “beef taste”

8. Influence of Other Sensations on Taste
Temperature and texture enhance or detract from taste
A lot of what we smell is based on pain sensors (Chili peppers, ammonia, etc.)

9. Aging:
Chemical senses – few problems occur until the fourth decade, when these senses begin to decline

10. Chunk and Chew: Partner A: Partner B:
Please explain what is needed for smell to occur and describe the pathway from odor molecules to the brain.
Partner B:
Please explain the two types of epithelial cells found in taste buds that make the process of taste happen. Also, describe the pathway of taste molecules from the tongue to the brain.