Ion channels underlie a broad range of the most basic biological processes, from excitation and signaling to secretion and absorption. Like enzymes, they are diverse and ubiquitous macromolecular catalysts with high substrate specificity and subject to strong regulation. This fully revised and expanded Third Edition of Ion Channels of Excitable Membranes describes the known channels and their physiological functions, then develops the conceptual background needed to understand their architecture and molecular mechanisms of operation. It includes new chapters on calcium signaling, structural biology, and molecular biology and genomics. Ion Channels of Excitable Membranes begins with the classical biophysical work of Hodgkin and Huxley, continues with the roles of channels in cellular signaling, then develops the physical and molecular principles needed for explaining permeation, gating, pharmacological modification, and molecular diversity, and ends with a discussion of channel evolution. Ion Channels of Excitable Membranes is written to be accessible and interesting to life scientists and physical scientists of all kinds. It introduces all the concepts that a graduate student should be aware of but is also effective in advanced undergraduate courses. It has long been the recognized authoritative overview of this field used by all neuroscientists.