Mechanisms of Olfaction - Bioelectronic Nose: Integration of Biotechnology and Nanotechnology - page 23

Chapter 2
Mechanisms of Olfaction

Ruchira Sharma and Hiroaki Matsunami

Abstract Molecular mechanisms of olfaction have been intensively studied in the
last quarter century. Receptors by which olfactory stimuli are detected are vastly
different between different animal species and even between different olfactory
organs of the same species. This chapter includes a description of the anatomy of
the mammalian olfactory system and an overview of the receptors. The signaling
mechanism and expression pattern of these receptors is discussed along with how
the brain decodes olfactory information gathered from the environment and then
translates these signals into behaviors. This chapter also contains brief comparison
of the fish, insect and nematode olfactory receptors.

2.1 Importance of Olfaction

A sense of smell is crucial for the survival of any species, and in our own experi-
ence, we detect dangers like fire or spoilt food with our noses. The hedonistic plea-
sure derived from eating and drinking is also heavily reliant on the sense of smell.
Olfaction is an important tool used in so many facets of animal life and is often the
deciding factor between surviving an encounter with a predator, passing on genes to
offspring and finding a source of food. Although Santiago Cajal described the pe-
ripheral olfactory system in 1891, very little was uncovered about the mechanisms
of odor detection and differentiation in the next 100 years, and the olfactory system
continues to elude our understanding. The method by which sensory inputs are con-
verted to behavioral output is still a mystery.