Dresden 2009 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 14: Neuronal and Sensory Systems

BP 14.1: Hauptvortrag

Mittwoch, 25. März 2009, 14:00–14:30, HÜL 186

Nerve signals as density pulses, conduction events, and the role of anesthetics — •Thomas Heimburg — Niels Bohr Institute, University of Copenhagen, Denmark

It has long been known that nerve pulses are accompanied by a reversible heat exchange. After a first phase of heat release the heat is practically completely reabsorbed into the nerve membrane. This indicates that the fundamental physical processes underlying nerve action are predominantly of reversible nature. The famous Hodgkin-Huxley model, however, relies on dissipative processes, i.e., on electrical ion currents flowing through resistors (ion channel proteins). Here we show that under physiological conditions there is the possibility of electromechanical soliton generation. This notion is supported by the fact that during nerve pulses various mechanical changes are experimentally observed. The necessary requirement for solitons is a melting transition in the biomenbranes slightly below physiological temperature leading to a nonlinear compressibility. This transition is in fact present in biomembranes. Interestingly, exactly in these transitions one finds quantized ion currents through membranes that are indistinguishable from those reported for ion channel proteins. Anesthetics influence these processes because the induce melting point depression. Thus, they render the pulse excitation more difficult. Again, this is in agreement with data on real nerves. Further, anesthetics are able to "block" the conduction events through membranes.