Taste

Taste, gustatory perception, or gustation is one of the five traditional senses. Taste is the sensation produced when a substance in the mouth reacts chemically with receptors of taste buds.

Taste, along with smell (olfaction) and trigeminal nerve stimulation (with touch for texture, also pain, and temperature), determines flavors, the sensory impressions of food or other substances.

Humans perceive taste through sensory organs called taste buds, or gustatory calyculi, concentrated on the top of the tongue. There are between 2000 and 5000 taste buds that are located on the back and front of the tongue. Others are located on the roof, sides and back of the mouth, and in the throat.

The sensation of taste can be categorized into five basic tastes: sweet, bitter, sour, salty and umami. Taste buds are able to differentiate between different tastes through detecting interaction with different molecules or ions. Sweet, umami, and bitter tastes are triggered by the binding of molecules to G protein-coupled receptors on the cell membranes of taste buds. Saltiness and sourness are perceived when alkali metal or hydrogen ions enter taste buds, respectively.

As taste senses both harmful and beneficial things, all basic tastes are classified as either aversive or appetitive, depending upon the effect the things they sense have on our bodies. Sweetness helps to identify energy-rich foods, while bitterness serves as a warning sign of poisons.

The basic tastes contribute only partially to the sensation and flavor of food in the mouth — other factors include smell, detected by the olfactory epithelium of the nose; texture, detected through a variety of mechanoreceptors, muscle nerves, etc.; temperature, detected by thermoreceptors; and "coolness" (such as of menthol) and "hotness" (pungency), through chemesthesis.