So ligand gated ion channels are these channels that respond to the binding of a special type of molecule. And once that molecule binds, so let's say this green molecule is the ligand, it binds onto the outer portion of this transmembrane protein we call a ligand gated ion channel. Once it binds, let's say, on the outside, it causes a conformational change that opens up the internal pocket of that particular transmembrane protein. And then some type of ion can flow across that membrane from one side to the other side. In this case, let's say it's from the outside to the inside of the cell. So this is the sodium ion flowing in this direction.