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

12 BME 4900 Final ReportTeam 8neuron to receive multiple stimuli, and is necessary if the neurons are to respond to bothexcitatory and inhibitory inputs.Figure 8. An example of a dendritic tree with multiple branches. The branches converge andterminate at the soma compartment (rightmost subcircuit).In order to accurately model dendrite behavior, the values for the threecomponents must be determined. For this device, it is assumed that the dendrites willhave uniform dimensions and can reasonably be modeled as cylinders. Under theseassumptions, the axial and membrane resistances may be calculated as a function of thecylindrical compartment’s diameter and length (see Eq. 1 and 2).(1) (2)Equations 1 & 2. Determining the medial and axial resistance of a dendrite compartment as afunction of length (l) and diameter (d). Note that R M refers to the specific membrane resistanceand R A refers to the specific axial resistance.Two aspects of the dendrite circuit are being monitored in order to correctlymodel this portion of the neuron: voltage decay and the time constant(s) for thedendrite. The voltage decay is a major factor in determining if the stimulus received willbring the membrane potential at the axon hillock above threshold. The amplitude of theinput current and the simulated dimensions of the dendrite affect the percentage ofvoltage lost. By manipulating the axial resistance and the number of compartments inthe dendrite (largely simulating the length of the dendrite), the voltage decay can bemonitored and analyzed (see Fig. 9). The data gathered shows that as the axial resistance