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Harold Sabbagh

An Electrical Engineer Looks at Medicine and Biology

This presentation is based on class notes developed by Professor Sabbagh for ECE201C at Purdue during the Fall of 2002. The notes were the basis of a final course project on pspice. We start by modeling nerve axons by electric circuits, which are then analyzed using pspice. The physiology of the nerve cells is also modeled by the circuits. We apply various input signals to the electric circuit, and demonstrate interesting results from the pspice analysis that correspond directly with the observed 'action potentials' on the giant axon of a squid, in agreement with the Hodgkin-Huxley model that garnered them the Nobel prize in physiology in 1957. This leads to the notion of the axon as being a nonlinear, nondispersive delay line. We then contrast the neuron of a squid with that of animals, including humans, and develop an equivalent electric circuit for that neuron. The fundamental difference between the two neurons is the presence of a myelin sheath in the human neuron. We have not computed the pspice response of the human neuron: that will left for the interested student. We will discuss what one might learn about such diseases as multiple scleroses from the human neuron electrical model.