re AX reAX P. WW WWWW WWW im AX li TAX ri AX X Figure 6.1. The Linear Core-Conductor Model for a single fiber lying in a restricted extracellular space. Longitudinal extracellular and intracellular currents are fe and It. while extracellular and intracellular potentials are designated + and +, respectively. AX CAAX ade =-leTe (6.1) =-liri (6.2 = -1m (6.3) Ole = im + ip (6.4) 120- Um Oum - Um = rexzip (7.14) at3. (10pts) Represent the following three current excitation configurations in mathematical terms, i.e. show what would appear on the right hand side of Equation 7.14. a) a needle electrode outside an axon. The current from the electrode is a DC current and the width of the electrode is one tenth of a space constant. b) a cuff electrode, again outside the axon, generating a biphasic current at a pulse rate of 20kHz. The current amplitude is +200uA. The length of the cuff is 10 space constants c) The electrode is a conductive nanopolymer inside the cell (Professor Christine Payne in the School of Chemistry and Biochemistry at GT does work on these). Under an external 10kHz voltage pulse, the nanopolymer will generate a 10us current pulse inside the cell. The particle diameter is roughly 50nm