Publisher Summary This chapter examines the dynamics of ion channels using methods similar to those introduced by Hodgkin and Huxley in 1952. Ion channels are a class of multimeric transmembrane proteins with a hydrophilic pore that facilitates transport of ions across the cell membrane. The size of the ion channel pore and the charge of amino acids near the opening of the pore help exclude entry of some ions while promoting the entry of others. This confers upon the ion channel a selective permeability to different ions. Several factors can induce conformational changes in the ion channel, altering its quaternary structure and therefore its permeability. These factors are referred to as gating variables because they function as a gate between the ion channels' different conformational states. Most ion channels are classified according to the nature of their gating and their selectivity of ions. The largest subclasses of ion channels classified by gating are the ligand-gated and voltage-gated ion channels. Ligand-gated ion channels change conformation when a ligand binds to them. The most common ligand-gated ion channels found at the post-synaptic membrane of neurons include NMDA, kainate, AMPA, and GABAA receptors.