Localized short impulses in a nerve model with self-excitable membrane.

During the generation and transmission of nerve impulses, the cytoplasm behaves like an excitable medium that self-regulates the shapes and magnitudes of the output excitation. In connection with this self-regulatory function, one can readily think of the plasma membrane as a nerve organ holding the key role in the mechanisms of generation and transmission of the transmembrane potential, namely, it is expected to provide the essential feedback that stabilizes the stimulus. Here, a simple and coherent picture of self-regulation of the nerve impulse is proposed in terms of one single feedback associated with the main excitable biological organ of the nervous system. In this purpose, an electrodynamic theory is developed within the framework of a cable model in which the membrane capacitor is regarded as a charge-management electrical component with a defined capacity-voltage characteristic. It is found that in both myelinated and myelin-free nerve fiber contexts, the transmembrane excitations are well-localized short impulses whose shape and stability are determined by the capacity-voltage characteristic assumed to govern the self-excitability properties of the nerve membrane.