Smell & Taste
Chemoreceptors are nothing special: even single-celled organisms use them to explore their environment. But just as a single note does not make music and a scale does not make a symphony, it is only through the interaction of many sensory modalities that humans can have an experience worthy of five stars in the Michelin Guide.
Our tongue can only taste sweet, sour, salty, bitter, and umami. Umami is a tongue stimulus that indicates the presence of protein. It was the last of the five tastes to be discovered. Our nose, on the other hand, has 350 types of receptors that enable us to distinguish between thousands of smells. That is fewer than dogs or mice, but it is perfectly adequate for everyday life, in which we never perceive smell and taste stimuli in isolation, but always as a concert.
A concert in which sensory impressions play first fiddle, but which would not sound harmonious without feelings, thoughts, and, above all, memories. When the scent of fresh pine needles fills your nose in December or a hint of sunscreen in July, your brain instantly generates a whole world.
Unpleasant smells and tastes have other, more short-term consequences. But whenever they activate our vomiting center, they may have saved our lives.
