| The sense of taste (gustation) and smell (olfaction)
depend on chemoreceptors that detect specific chemicals in the
environment. These
chemical senses are usually closely related, and in aquatic environments
there is no real distinction. In humans and other mammals, the chemical
senses of gustation and olfaction are interrelated. In both cases, a
small molecule dissolves in liquid to reach the receptor cell and
stimulates the sensation. That molecule binds to a specific protein in
the receptor cell membrane, triggering a depolarization of the membrane
and the release of a neurotransmitter.
The receptor cells for taste are organized into taste buds located
in several areas of the tongue and mouth. There are four basic taste
perceptions - sweet, sour, salty, and bitter - each recognized in a
different region of the tongue. Sensory data transmitted by sensory
neurons from taste buds to the brain represent the differential
stimulation of the various classes of receptors. With each thing we
taste, the brain processes the signal from the taste buds, and a complex
flavor is discerned. |
