Question

......Why does the polarity of the extracellular recording change as the stimulus position changes, i.e., as the simulated action potential propagates past the electrode? ​

.....Why is the maximum voltage value not the same for intracellular and extracellular recordings? ​

Answer 1

change in polarity occurs due to the change in the charge of cell or extracellular region. Movement of positive or negative charge leads to change in polarity. When concentration of positvely charged ion is more in the cell then the cell become depolarized and highes concentration of negative charge inside the cell leads to hyperpolarization.

Same in the case of extracellular region.

Inside the cell concentration of potassium, magnesium is high. Outside the cell sodium, chloride and calcium concentration is high. That is why the voltage is different for outside and inside the cell.