The Organization of Nervous Systems

Nervous systems employ some or all of the senses to convert energy at the level of receptor cells into neural information. This conversion generates electrochemical signals carried centrally that, via a series of additional neurons, determine behavior. The most obvious behaviors are those mediated by skeletal muscles, cardiac muscles, smooth muscles, and glands. But motor responses are members of a longer list that includes attention, perception, emotion, memory, thought, motivation, and others. How to describe these additional “systems,” and how to decipher what the relevant circuits do and how they do it, are unanswered questions. This chapter describes the main features of neural processing, asking whether the principle of neural function is simply to make associations that lead to useful behaviors.