| The
Senses of Smell and Taste The senses
of smell and taste are chemosenses and belong in the chemical
sensing system.
The processes of smelling and tasting are complex.
They begin when molecules are released by substances that stimulate the sensory cells in
the nose, mouth, or throat.
- Olfactory nerve cells are stimulated
by odors. They are found in tissue located high inside the nose, and connect directly to
the brain.
- Gustatory nerve cells are stimulated
by the taste of food and beverage. They are located in the taste buds of the mouth and
throat.
These sensory cells transmit messages to the brain
through the nerves, where specific tastes and smells are identified.
Another chemosensory process, called common
chemical sense, also contributes to smell and taste. These cells alert the brain
to sensations such as heat (as from peppers) or cool (as from menthol).
How do taste and smell
interact?
The four basic taste sensations are:
When these tastes, along with texture, temperature,
and information from the common chemical sense, combine with odors, the perception of flavor
occurs. Flavor defines the food that is eaten, and is recognized mainly through the sense
of smell.
Source: National Institute on Deafness and Other Communication
Disorders\ |
Smell and
Taste Disorders (Chemosensory Disorders)What are smell and
taste disorders?
The loss of the senses of smell (anosmia) and taste (ageusia)
are the most common chemosensory disorders.
The reduced ability to smell (hyposmia) or to taste sweet, sour,
bitter or salty substances (hypogeusia) are also common.
In other disorders of the chemosenses, odors, tastes, or flavors may be misread or
distorted, causing a person to detect an unpleasant odor or taste from something that is
normally pleasant to taste or smell.
Smell disorders are serious because they damage the early warning system that can alert
a person to such things as:
- fire
- poisonous fumes
- leaking gas
- spoiled food and beverages
Abnormalities in taste and smell can accompany or indicate the existence of diseases or
conditions such as:
- degenerative diseases of the nervous system such as:
- Parkinson's disease
- Alzheimer's disease
What causes smell and taste disorders?
Although some people are born with chemosensory disorders, most are caused
by:
- illness (i.e., upper respiratory infection, sinus infection)
- injury to the head
- hormonal disturbances
- dental problems
- exposure to certain chemicals
- certain medications
- exposure to radiation therapy for head or neck cancer
How are smell and taste disorders diagnosed?
In addition to a complete medical history and physical examination,
diagnostic procedures may include:
- measuring the lowest concentration of a chemical that a person can recognize
- comparing tastes and smells of different chemicals
- "scratch and sniff" tests
- "sip, spit, and rinse" tests where chemicals are directly applied to specific
areas of the tongue
Treatment for smell and taste disorders:
Specific treatment will be determined by the physician(s) based on:
- patient’s age, overall health, and medical history
- extent of the disorder
- expectations for the course of the disorder
- patient’s tolerance for specific medications, procedures, or therapies
- patient’s (or family’s) opinion or preference
Treatment may include:
- stopping or changing medications that contribute to the disorder
- correction of the medical problem that is causing the disorder
- surgical removal of obstructions that may be causing the disorder
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