Exam 4: Sensation and Perception

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The sense of taste (gustation)involves receptor cells that respond to four basic stimulus qualities:sweet,sour,salty,and bitter.A fifth category also exists,a flavor called umami,although there is controversy about whether it qualifies as a fundamental taste.Umami is a hard-to-translate Japanese word,although the English "meaty" or "savory" comes close.Chemically,umami involves food stimuli that contain amino acids (the substances that make up proteins).Examples are:sweet-sugar; sour-lime; salty-curry; bitter-bitter melon; umami-seaweed.
Although the specialization of the receptor cells leads them to respond most strongly to a particular type of taste,they also are capable of responding to other tastes as well.Ultimately,every taste is simply a combination of the basic flavor qualities,in the same way that the primary colors blend into a vast variety of shades and hues.
The receptor cells for taste are located in roughly 10,000 taste buds,which are distributed across the tongue and other parts of the mouth and throat.The taste buds wear out and are replaced every 10 days or so.That's a good thing,because if our taste buds weren't constantly reproducing,we'd lose the ability to taste after we'd accidentally burned our tongues.
The sense of taste differs significantly from one person to another,largely as a result of genetic factors.Some people,dubbed "supertasters," are highly sensitive to taste; they have twice as many taste receptors as "nontasters," who are relatively insensitive to taste.Supertasters (who,for unknown reasons,are more likely to be female than male)find sweets sweeter,cream creamier,and spicy dishes spicier,and weaker concentrations of flavor are enough to satisfy any cravings they may have.
In contrast,because they aren't so sensitive to taste,nontasters may seek out relatively sweeter and fattier foods in order to maximize the taste.As a consequence,they may be prone to obesity.