Gustatory system

From ArticleWorld

The gustatory system is a sensory system in many animals that is concerned with the sense of taste. Taste involves receptors on the surface of the tongue and on the back of the mouth. The taste sensation is sent back to the brain via small branches of the cranial nerves X-XII.

Origin

Scientists believe that the original purpose for the sense of taste was for an animal to detect the presence of something that would be toxic to them if eaten. The sensation of bitter is particularly associated with toxic substances. Scientists have come to recognize a great deal of variability even among humans in their ability to detect the bitter flavor. There is a subclass of “super tasters” who are particularly sensitive to bitterness. The sensation of taste in humans, however, is generally considered a pleasurable ability.

Physiology

The surface of the tongue is covered with small papillae, or projections, of tissue. Each of these papillae is covered with 200-300 taste buds. Taste is difficult to determine under dry conditions. Saliva helps put dry substances into a more liquid form where the various molecules, such as sodium chloride (salt), sucrose (sugar), hydronium ions (from acid) and glutamates can be detected as salty, sweet, sour and savory, respectively. Each taste bud has a nerve fiber at its base which transmits the taste impulse up to the brain.

Disorders

There are several disorders of the gustatory system. Hypogeusia involves a diminished ability to detect tastes. Ageusia is rare and involves the complete absence of the ability to taste. Dysgeusia occurs when someone senses a bad taste from something that is normally pleasant tasting or when an individual has a persistent sensation of a bad taste.

Disorders of the gustatory system, also called chemosensory disorders, can be congenital or acquired. Certain injuries that disrupt the nerves to the tongue receptors or infections can result in acquired loss of taste. Cancer patients who receive radiation to the head and neck can lose their sense of taste. Medicines, insecticides or other chemical exposure can reduce an individual’s ability to taste.