Sensory cells and sensory organs

Abstract

Animals possess sensory organs that collect information and convey this information to the central nervous system. This introductory chapter outlines how sensory cells perform their task of detecting adequate stimuli and how they produce electrical signals that encode information for the brain. In the course of animal evolution, the specific transduction mechanisms that operate in the various sensory cells have been optimized under intense selective pressure. The results of this process often include extreme sensitivity for the adequate stimuli and efficient signal amplification. To illustrate different solutions to the problem of detecting and encoding complex information, the sensory modalities of touch, vibration detection, hearing, vision, and olfaction are briefly introduced on the levels of key cell structures and transduction molecules. Pain perception is described as a sensory modality with very special features that differ fundamentally from those of other modalities. Thus, polymodality of sensory cells, modulation by the immune system, and suppression by endorphins represent characteristic properties of the pain system, linked to its unique protective function. This chapter is designed to direct the reader’s attention to some central points of the topic. It does not deal with the subject of sensory detection in a comprehensive way. It rather highlights a set of particularly important aspects of sensory transduction that may be of interest for the interdisciplinary approach followed in this book. Questions of sensitivity, selectivity, and adaptation in sensory cells are directly related to the mode of perception that defines our view of the world. Inasmuch as our sensory organs have been shaped by evolution, our perception of reality is the consequence of evolutionary forces and constraints as well.