Senses: Tasting

Your Sense of Taste

The following is excerpted from A Primer on Taste.

Tastebuds alone can detect only sweet, sour, salty, and bitter. “If you lick a pink ice cream cone,” says Donald Leopold, an otolaryngologist at Hopkins’s Bayview Medical Center, “your tongue tells you it’s cold and sweet and smooth, but your sense of smell tells you it’s strawberry. Probably 80 percent of what you eat, you appreciate through your sense of smell.” That’s why if you have a cold, you could mistake a bite of onion for apple.

If smell is so crucial to taste, why do we have tastebuds?

Authorities agree that tastebuds have high survival value. They screen our food for important molecules that do not vaporize– salt, for instance–and therefore cannot be smelled.

Hungry Forefather: ‘Hmm. Is this good to eat?’ He nibbles. ‘Hey, it’s sweet!’ Kneeling, he crams berries into his mouth. Sweetness marks glucose, a good source of energy.

Ten feet away, Foremother makes a face and spits. The root she just sampled tastes bitter, a characteristic of many poisons. She moves over to the berries.

Humans and other animals are overwhelmingly attracted to sweetness, and it is the taste that degrades least in old age. We also crave salt, a universal bodily need; wars have been fought over salt. As for sour, the taste of high acidity, Kenneth Johnson, scientific director of Hopkins’s Krieger Mind/Brain Institute, suggests it’s a marker for hydrogen ions.

Some neuroscientists would add a fifth basic taste: delicious, a translation of the Japanese word ‘umami.’ Delicious is defined by the taste of MSG, a flavor-enhancer that was first isolated from a seaweed the Japanese had been adding to food for centuries. And what is MSG? monosodium glutamate, an amino acid. As a rule, the taste ‘delicious’ signals amino acids, building blocks of protein, therefore good for you.

And there you have it: As with sex, crafty Nature has put the pleasure principle to work. In general, what tastes good will keep the species going. What does not, may not….

So tell me about tastebuds. Where are they, and how do they work?

Go to a brightly lit mirror and take a good look at your tongue, something you may not have done since fourth grade. You’ll see bumps scattered on the surface, small round ones at the front and sides, larger ones in the back. These are technically called papillae, from the Latin word for bumps.

Each bump has from one to several hundred tastebuds (visible only with a microscope), and each tastebud has 50 to 150 taste receptor cells (taste cells). In all, most people have 2,000 to 5,000 tastebuds.

So, in comes a forkful of food. Gnash, gnash, chop, chop, work the tongue, pause to savor. Specialized receptors all over the mouth take note of texture, temperature, and nippy spices, while each taste cell reacts to the nearest molecule of food. It reports its verdict–sweet, sour, bitter, or salty–by firing an action potential, launching an electrical signal that eventually reaches the brain.

Receptors near the tip of the tongue are especially sensitive to sweetness. Salty and sour tend to be sensed on the sides of the tongue, and bitterness at the rear. But of course sweet can be tasted somewhat at the back of the mouth, bitter at the front, and so on.

Nor are the taste cells themselves rigidly specialized. Experiments show that while each has a taste it consistently prefers, 9/10ths report on two or more of the basic tastes. Taste cells also vary in their threshold; a cell might prove impervious to sucrose, but respond to the much sweeter saccharine.

These variations help the nervous system sort flavors out with some precision. Tea, for instance, causes rapid firing from receptors for both acidity and bitterness, plus sweetness signals depending how much sugar you put in.

The tongue’s message to the brain, then, is more like a symphony than a single tune-up A. The action potential from each taste cell–let’s be conservative and say some particular mouth has 300,000 of them–zings up the nerve axons into the brain stem, the thalamus, and finally the cortex. The cortex also gets reports about temperature and texture and delivers the conscious experience of the bite: Strawberry ice cream, but let’s not buy this brand again. It’s too sweet.

From A Primer on Taste

Taste & the Sacral Chakra

Taste is associated with the sacral (2nd) chakra, which governs self-gratification, nurturing and identification with the emotional body. Depth of feeling, sexual fulfillment and the ability to accept change flow as a result of the second chakra too. No wonder psychologists equate foods we select with characteristics of our personalities.

Fun Facts

Probably 80% of what you perceive as taste actually comes from smelling functions.

Chili peppers do not stimulate a heat receptor but actually chemically irritate or burn pain receptors in the mouth. Perhaps people who love spicy food have a bit of a culinary S&M fetish!

Compiled fun facts about all the senses

Continued Learning

Super great content made for curious birds without a science background.

A Primer on Taste – Johns Hopkins Magazine

That’s Tasty! – Neuroscience for Kids

In Short: Taste & Smell – Johns Hopkins Magazine

Are you a supertaster? – BBC Science & Nature: Human Mind & Body

Flavour and personality – BBC Science & Nature: Human Mind & Body

Taste, BBC Science & Nature: Human Mind & Body

Chakras Chart: shows corresponding sense, area of consciousness, color vibration, musical vibration, gland, nerve and system of the body and element – The Brofman Foundation for the Advancement of Healing

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