Primary taste sensation:
The five basic tastes—sweet, bitter, sour, salty, and umami—result from a chemical reaction between stimuli (food) in the mouth reacting with receptors (taste buds).
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| Special sense- Taste and Smell |
Sweet- The most elemental of taste pleasures, sweetness signals the presence of sugars, the foundation of the food chain and a source of energy. Today, though, our sweet tooth is overstimulated by an avalanche of sugar in our diet.
Bitter- A poison alarm, bitterness is a distinctive bad taste accompanied by a reflexive “yuck” expression on the face. Hundreds of substances, mostly found in plants, taste bitter. But a little bitterness makes food interesting—and healthy. Antioxidants, which aid metabolism and help the body ward off cancer, account for much of the bitter taste of kale, dark chocolate and coffee.
Salty- Our brains are programmed so that a little salt tastes good, and a lot tastes bad. This ensures we consume just enough to maintain the salt balance our bodies need to function. But beware—your palate can adapt to crave a lot of salt, as in the case of people who eat the typical American diet. The good news: If you cut back on salt, your taste buds can adapt to be satisfied with less.
Sour- The mouth-puckering sensation is caused by acids in lemons, yogurt and sourdough bread and other food. Scientists aren’t sure exactly how it works, or even its precise biological purpose, but many suspect that sourness originally signaled that food was decomposing and was potentially unsafe to eat.
Umami- Japanese for “delicious taste,” umami is produced by certain amino acids. It’s best described as “savory”—a taste rich in flavor released by cooking, curing or aging. Examples of umami foods include seared and cured meats, aged cheeses, fish sauce, green tea, soy sauce and cooked tomatoes.
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| Taste |
Taste buds:
Taste buds contain the taste receptor cells, which are also known as gustatory cells. The taste receptors are located around the small structures known as papillae found on the upper surface of the tongue, soft palate, upper esophagus, the cheek, and epiglottis.
There are three types of taste buds papillae:
Fungiform papilla- The fungiform papillae are broad flat structures that house taste buds in the central portion of the dorsum (back) of the tongue. These papillae were thought to resemble a fungus: a little mushroom. Fungiform means mushroom-shaped. From fungi-, fungus + forma, shape. Each fungiform papillae usually contains 3-5 taste buds.
Circumvallate taste buds papillae- Circumvallate papillae are located at the base of your tongue. They're large and round, and they house several thousand taste buds.
Foliate taste buds papillae- Their location is on the lateral sides of the tongue. The foliate papillae are involved in the sensations of taste and have taste buds embedded in their surfaces.
Taste blindness:
- The inability of a person to feel the taste of any item and to identify it.
- A reduction in sensitivity to bitter tastes as a result of having less taste buds.
- In taste blindness a person has fewer taste buds for each taste sensation .
- Some people are taste blind for certain substances, especially for different type of thiourea compounds.
- A substance used frequently by psychologists for demonstrating taste blindness is phenylthiocarbamide.
Causes of taste blindness:
- Upper respiratory infections, such as the common cold.
- Sinus infections.
- Middle ear infections.
- Poor oral hygiene and dental problems, such as gingivitis.
- Exposure to some chemicals, such as insecticides.
- Surgeries on the mouth, throat, nose, or ear.
- Head injuries.
- Try cold foods, which may be easier to taste than hot foods.
- Drink plenty of fluids.
- Brush your teeth before and after eating.
- Ask your doctor to recommend products that may help with dry mouth.
Lemon helps to restore back the sense of smell and taste. It fights the bacterial and viral infections thus makes the nasal passage clear. Mixing lemon juice and honey in a glass of water is an effective remedy to treat this problem.
Smell receptors and their location:
- Olfactory receptors are able to detect air-borne odour molecules that enter the nasal cavity and bind to olfactory receptors.
- There are 400 olfactory receptors (ORs) to detect odors, but there is currently no model that can predict olfactory perception from receptor activity patterns.
- Odorants dissolve in the mucus and bind to receptors. Dissolved odorants stimulate olfactory sensory neurons by binding to receptor proteins in the olfactory cilium membranes.
- An olfactory receptor has a life span of about one month.
Location:
Occupies the superior part of the nasal cavity and extending along the superior nasal concha.
Smell information also goes to the thalamus, a structure that serves as a relay station for all of the sensory information coming into the brain.
Abnormalities of olfaction:
What are the smell disorders?
- Hyposmia- is a reduced ability to detect odors.
- Anosmia- is the complete inability to detect odors. In rare cases, someone may be born without a sense of smell, a condition called congenital anosmia.
- Dysosmia- A distortion of the sense of smell.
What causes smell disorders?
- Aging
- Sinus and other upper respiratory infections
- Smoking
- Growths in the nasal cavities
- Head injury
- Hormonal disturbances
- Dental problems
- Exposure to certain chemicals, such as insecticides and solvents
- Numerous medications, including some common antibiotics and antihistamines
- Radiation for treatment of head and neck cancers
- Conditions that affect the nervous system, such as Parkinson’s disease or Alzheimer’s disease.