Smell and Taste Lab

Smell & Taste

HASPI Medical Anatomy & Physiology 11d

Odor and Food Receptors  

Smell and taste are important senses capable of alerting us to danger within the environment, while at the same time allowing us to find pleasure in food and scents.  These special senses are closely linked, and in fact our sense of taste would be quite boring without our sense of smell.  The processes of smell and taste are actually quite complicated, but in both cases they begin when a molecule of a substance contacts special receptors in our nose or in our mouth.

These molecules must first diffuse into the mucous within our nasal cavity or saliva within our mouth and then reach ciliated neurons capable of binding to these molecules.  The neurons transmit a message to the brain, which interprets what it is we smell or taste.

Smell or Olfaction  

Humans are capable of detecting more than 10,000 different odors.  More than 50 million specialized receptor cells are located at the upper portion of the nasal cavity in a sheet of cells called the olfactory epithelium.  In comparison, canines have more than 200 million olfactory cells, which explains their heightened sense of smell.  These receptors are concentrated in a structure called the olfactory bulb that is embedded in the olfactory epithelium and is actually the end of the olfactory nerve.  The ends of olfactory neurons are covered with cilia (tiny hair-like structures) that have smell receptors covering the surface.   

Taste or Gustation  

Every human is born with a specific number of taste buds, and this number varies widely from person to person.  The sense of taste is hereditary.  Do you have friends that find coffee bitter or that cannot tolerate spicy foods, while others love both?  This is because they have a different concentration of papilla, and therefore taste buds.  Taste buds are located in the papilla found on the surface of the tongue.  Different types of papilla are located on different portions of the tongue and have different arrangements of taste buds. 

A study by Linda Bartoshuk determined that there are three groups of tasting ability: supertasters, normal tasters, and non-tasters.  Approximately 25% of the U.S. population is a supertaster, 50% are normal, and the other 25% are non-tasters.  Supertasters have a much higher concentration of taste buds and therefore experience the texture, temperature, and taste of food at a higher level than a non-taster.  Every taste bud is surrounded by pain nerves, which means that supertasters are usually much more sensitive (and tend to stay away from) spicy foods.

When Smell and Taste Go Bad  

There are several conditions or disorders that can affect our sense of smell and taste.  These most often result from infection, smoking, or drug use, and/or trauma to the nerves associated with each sense.  In some cases these disorders may only last for a short period of time.  More than 4 million Americans experience disorders of olfaction and gustation annually.  These may include:

• • • • • • • Ageusia – lack of taste
            • Anosmia – lack of smell
            • Dysgeusia – distorted tastes
            • Dysomnia – distorted smells
            • Parosmia – all substances smell bad
            • Phantosmia – smelling substances not there
            • Hyperosmia – overly acute sense of smell
            • Hypogeusia – decreased sense of taste
            • Hyposmia – decreased sense of smell