Chapter 2

Chapter summary

The senses of smell (olfaction) and taste (gustation) are known as chemical senses because their receptor neurons extract information by means of chemical interactions.

Smell is mediated by olfactory receptor cells in the nose, which connect to mitral cells in the olfactory bulb. Different substances create different patterns of activity across the mitral cells. Our ability to recognise thousands of different odors is based on distinguishing different patterns of activity in mitral cells. The sense of smell acts as an early warning system signalling whether to approach or eat the source of a smell.

Gustatory receptors fall into five categories which relate to five types of substance, namely sugars, salts, acids, plant alkaloids, and amino-acids. Tastes can be decomposed into corresponding contributions from five taste qualities—sweetness, saltiness, sourness, bitterness, and savouriness or umami. The sense of taste detects these five types of important substance in order to regulate their intake.

Food flavor during eating involves an interaction between several perceptual sensations including taste, smell, temperature, touch, sight, sound, and pain. Multi-modal brain cells that respond to combinations of smell, taste, and sight may mediate flavor sensations.