1. THE CHEMICAL SENSES: TASTE AND SMELL
The senses of taste (gustatory) and smell (olfactory) are stimulated by chemical substances interacting with the receptor cells of the tongue and nose, respectively

2. TASTE
The sense of taste is designed not only to allow pleasurable, nourishing food in, but to keep dangerous, toxic foods out, of our digestive system → the stimuli for the sense of taste are soluble (dissolvable in water/saliva) food molecules

3. TASTE
Inside each bump on your tongue are over 200 taste buds, each containing a pore with 50 to 100 receptor cells projecting tiny hairs → different receptors respond to the different taste sensations of sweet, salty, sour, bitter, and umami (savory, meaty taste)

4. TASTE
→ stimulation of receptor cells triggers neural impulses that pass through the thalamus on their way to the insular cortex in the frontal lobe

5. TASTE
We are born with certain taste preferences, but individual preferences vary based on what we are exposed to socially and culturally, as well as our own taste bud density → we learn many preferences based on what we were fed when we were young

6. TASTE
→ taste bud density based on genetics also influences taste perceptions: supertasters with more receptor cells are more sensitive to certain tastes than nontasters who are less sensitive * Women and the young (we lose receptors as we age) are most likely to be STs

7. SMELL
We smell (olfaction) something when its evaporated chemical substances enter our nostrils and dissolve in mucus → our olfactory receptor cells number 20 million and like taste cells are constantly being replaced

8. SMELL
The hair-like receptor cells – olfactory cilia – cluster at the top of the nasal passage and respond selectively and in different combinations to specific aromas → the 10,000+ odors we can identify travel along the axons of receptors, then to the olfactory bulb and straight on to the olfactory cortex in the temporal lobe

9. SMELL
* Unlike the other sensory systems, smell does NOT pass through the thalamus

10. SMELL
Smell is closely associated with experience, emotion and memory: a positive experience or emotion linked with a scent causes us to like that scent → we have trouble identifying odors w/o our eyes, but we easily associate long forgotten odors and memories