The Human Brain : From Neurone to Nervous System


  1. The cell membrane is a lipid bi-layer that separates the intra- and extra-cellular fluids. Sodium ions are actively pumped out of the cell in exchange for potassium ions , a process that depends on the sodium-potassium pump which uses energy in the form of adenosine triphosphate (ATP); this pump creates differences in the ionic composition of these fluid compartments.

  2. Neurones have a transmembrane potential, with the inside of the neurone being negative with respect to the outside. This potential is dependent on the presence of potassium channels in the neuronal cell membrane

  3. The neuronal cell membrane consists of a bi-lipid layer with a high electrical resistance, and containing protein insertions such as passive channels and active pumps that allow the movement of ions.

  4. This membrane separates the intra- and extra-cellular fluids, which have different ionic compositions.

  5. The presence of channels that allow only selected ions to move across the membrane allow the generation of a transmembrane potential; this Resting Potential is largely due to the permeability of the membrane to potassium ions.

Key Words: Active Transport; Sodium-Potassium Pump; Ion channels; Electrochemical Equilibria; Nernst Equation; Membrane permeability to ions.