Effect of time-varying magnetic fields on the action potential in lobster giant axon

The possible influence of time-varying magnetic fields on action potential in the lobster giant axon was studied. The axon membrane was excited by galvanic stimulation and the action potential was recorded intracellularly with microelectrodes. During the propagation of the action potential along the axon, alternating or pulsed magnetic fields were applied across the middle part of the axon to study whether or not magnetic fields have any effect on parameters such as conduction velocity and refractory period of the nerve fibre and amplitude, duration and shape of the action potentials. No effect on these parameters was observed under different flux densities and frequencies of the magnetic fields. When simulating the conductive properties of tissue surrounding the nerve with the aid of an external conducting loop with a load resistance, action potentials were generated which made it possible to study the threshold value of the induced eddy current for nerve excitation. Based on the results of the experiment, the influence of magnetic flux density, frequency, conductivity, induced EMF and induced eddy current density is discussed, and a method is proposed for estimating the threshold values of magnetic flux density for nerve excitation.