The opening of channels that let positive ions flow out of the cell (or negative ions flow in) can cause hyperpolarization. Examples: Opening of channels that let
+
K
+
K, start superscript, plus, end superscript out of the cell or
−
Cl
−
C, l, start superscript, minus, end superscript into the cell.
The opening of channels that let positive ions flow into the cell can cause depolarization. Example: Opening of channels that let
+
Na
+
N, a, start superscript, plus, end superscript into the cell.
The opening and closing of these channels may depend on the binding of signaling molecules such as neurotransmitters (ligand-gated ion channels), or on the voltage across the membrane (voltage-gated ion channels).
