BME 4900 Final Report - Biomedical Engineering - University of ...

14 BME 4900 Final ReportTeam 8be incorporated: a current stop to prevent backflow into the dendrite from the axon. Thediode would typically be used to create such a stop, but due to the voltage loss over thediode, an alternative method is used. The precision diode operational amplifier circuithelps to eliminate the voltage drop over the diode while still allowing for the backflow tobe stopped. It is followed by a voltage follower operational amplifier circuit (see Fig. 10).Multisim analysis of the compartment’s circuit shows a current backflow ofapproximately 53 nA, which is an acceptable backflow given the amplitudes we aredealing with in the model.Figure 10. A generalized schematic of the soma compartment, including the current backflowstop. This circuit outputs to the axon compartment.AxonThe axon is final component of the neural unit and, consequently, the site ofaction potential generation and propagation. The pre-synaptic input, which crosses thepreviously discussed synapse and is conducted by the post-synaptic dendrites, finallyreaches the neuraon axon where a resulting neural action is produced. In the context ofour final design, several basic subcircuit designs can be repeated, with modification, tomimic the desired behavior of each neuron population. The design relies on theFitzHugh-Nagumo circuit model of a neuron, which is an adaptation of the empiricallydefined Hodgkin-Huxley model. This analog design provides a robust, cost-effective