1) A nurse noticed that one electrode of a pair of Ag/AgCl neural electrodes was dirty and cleaned it by scraping it with steel wool (Brillo) until it was shiny and bright. The nurse then placed the electrode back on the patient. How did this procedure affect the signal observed from the electrode and the electrode impedances?

2) You are seeking to design a 2 cm length tungsten microelectrode for intracellular recording of neuronal action potentials that have amplitude of 50mV. What should the area of the electrode be to discriminate action potentials from the noise? Show your calculations. Use the formulas for resistivity and thermal noise below: where L is the length of the wire, A is the cross sectional area of the recording site and? (52.8n? m) is the resistivity of tungsten at 293K. Where k is the Boltzmann's constant (1.38x10-23J/K), T is the absolute temperature (293K), R is the resistance, and f is the bandwidth for action potentials (500-6000hz).