This book is intended for undergraduates studying the biological and medical sciences. The field of excitable cell physiology is one which is found quite baffling by a significant minority of these students. My aim here is to provide a brief introductory account, based on a conceptual approach, rather than on a mathematical or historical description. Once the student has grasped certain basic ideas concerning excitable cell function, the individual examples which follow fit into a well-defined pattern. No attempt has been made to give credit in appropriate measure to the many scientists who...