Na+ voltage-gated channel closed (activation gate closed; inactivation gate open)K+ voltage-gated channel closed (activation gate closed)Na+ channel opens and is activated (activation gate opens; inactivation gate already open)Na+ channel closes and is inactivated (activation gate still open; inactivation gate closes)K+ channel opens (activation gate opensNa+ channel reset to closed but capable of opening (activation gate closes; inactivation gate opens)K+ channel closes (activation gate closes)