Methods:
Preparation:
A frog of species Rana pipiens (green with brown spots) was sacrificed and laid bare upon a dissecting plate. Using a pair of dissecting scissors the sciatic nerve was carefully massaged away from the femur (the nerve was a yellowish white color), and the in-vivo length (4.5 cm) was measured. The nerve was tied at its base at the knee, and musculature along the femur was cut exposing the point at which the nerve enters the hip. The leg was then severed from the hip. In order to maintain stable physiological conditions, the frog leg was bathed with liberal amounts of Frog Ringers (111.3 mM NaCl; 2.01 mM KCl; 1.58 mM CaCl2; 2.32 mM NaHCO3; .725 mM NaH2PO4) solution approximately every two minutes. The nerve was freed with a cut past the tie-point and it was placed within a Plexiglas recording chamber. The in-vitro length was measured to be 5 cm. The chamber was filled with a small amount of Frog Ringers solution in order to maintain a humid environment, however the level of the solution was maintained to ensure that the liquid never reached the wire electrodes (in order to maintain the stability of the signal recorded).
Recording:
Measuring the changes in extracellular potentials provides an easier method of observing action potentials than its intracellular counterpart. A pair of extracellular electrodes of opposite charge were used, therefore the negative charge generated by the current of Na+ into the cell, would register as a positive amplitude as it passed the first electrode and as a negative amplitude as it passed the second electrode. Due to this, the subsequent action potential propagation would result in a biphasic waveform. Since we were measuring signal within the sciatic nerve, the resulting electrical signal would be a compound recording (summation of activity from many axons). The sciatic nerve is a bundle of thousands of