The fourth edition of this highly successful text has been extensively revised and restructured to take account of the many recent advances in the field. The classic observations of recent years can now be interpreted with the powerful new techniques of molecular biology. Consequently, there is much new material throughout the book, including many new illustrations and extensive references to recent work. The text's essential philosophy remains the same, however: it clearly explains fundamental concepts, and examines key experiments in detail. This thorough and clearly written textbook will be valuable for students of physiology, neuroscience, cell biology and biophysics.