= Sodium channel
A <sodium channel> is an <ion channel> that preferentially conducts <sodium> ions. In a voltage-gated <sodium channel>, changes in <membrane potential> control opening and inactivation. Under usual neuronal conditions, opening permits inward current that promotes <depolarization>, recruiting more voltage-gated <sodium channels> during the rising phase of an <action potential>. <Molecular Biology of the Cell, 4th edition by Bruce Alberts and others>[Chapter 11, Voltage-Gated Ion Channels Generate Action Potentials in Electrically Excitable Cells]{ref}
An illustrative current relation is $I_{Na}=g_{Na}(V-E_{Na})$, with an explicitly chosen sign convention. Even a large conductance produces little net current near the sodium reversal potential. Channel availability, opening and ionic driving force are therefore distinct. Inactivation also differs from merely closing a resting activation gate: recovery depends on the preceding voltage history.
Back to article page
