9.1: Introduction

Ben Marcus, PhD (University of Chicago)

Austin Lim, PhD (DePaul University)

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In the previous two chapters, we examined some of the ways we detect and perceive our physical environment, including through phenomena such as light, sound, and tactile sensations.

In this chapter, we will complete our tour of the senses by exploring how we sense and perceive chemical compounds. In particular, we will describe the neural processes underlying our senses of smell, taste, and the chemical status of our internal homeostatic state.

Our olfactory system (smell) is activated by compounds called odorants, while our gustatory system (taste) is activated by compounds called flavorants. These two chemical senses are closely intertwined; odorants affect how we perceive taste, and bad tasting foods often smell bad. Try eating a fancy meal with a stuffed-up nose, and you’ll quickly notice that you lose the subtle complexities (and most of the joy!) of those foods.

Chemicals in our body, such as the amount of carbon dioxide in the blood or the presence of toxins in our digestive tract, are detected with our internal chemosensory systems. Many of these sensory systems are intimately tied with our autonomic nervous system (Chapter 2). Changes in chemical balance here results in unconscious or involuntary physiological changes to restore homeostasis.

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