The resting and excited states of biological membranes

In recent years, a vast body of information has been accummulated on the electrical properties of biological membranes. It has been found that electrical potential differences occur across them, that ions can penetrate them and that they have a quite high resistance to the flow of electric current through them. Analysis of this information has revealed that there is no general theory of membrane phenomena which can explain all of it. As well as these general phenomena, some cell membranes, particularily those of nerve cells, are capable of producing a temporary and localised change in membrane potential and membrane resistance, which is propagated along the membrane as an electrical impulse.An excitable membrane is nowadays regarded as being one of the basic functional units in a biological computer or control system and in view of its fundamental importance, it is hardly surprising that probably more information is available on the electrical properties of nerve membranes (particularily the giant nerve from the squid) than on any other membrane. A great deal is now known about the action potential, as the phenomenon of exitability is called, and despite the illuminating hypothesis of Hodgkin and Huxley, the problem of the exact physical chemical mechanism of excitability remains to be solved.All nerves are capable of conducting impulses and so are muscle cells; so also are certain. giant plant cells of the Characeae. Over the years the development of knowledge about the action potential in nerve has proceeded side by side with the study of the action potential in these plant cells and in this thesis the giant plant cell Nitella translucens has been chosen for studying biological membranes in both their resting and excited states. This chapter is concerned mainly with the theoretical basis of electrical phenomena in membranes in general, and with the electrical properties of biological membranes in particular