The Applet simulates the propagation of action potentials on a ring (the edge at the right is the same as the edge at the left). An action potential is initiated by applying a stimulus.

The start button generates one action potential which is blocked on the right so it only propagates to the left. The stop button stops the simulation, which can be resumed by pressing the cont. button.

• One can initiate more activations by clicking the mouse inside the graph.
• One can make the simulations faster or slower by using the respective buttons.
• The reset button brings the potential on all the cells back to the rest state.

To try: Stimulate at the back of the original wave (by clicking with the mouse) and generate two new action potentials which propagate in opposite directions. If the stimulus is too close to the back of the wave it will die out. But if it is during what is known as the vulnerable window, it will generate only one action potential which will annihilate the original one. The wave can also be killed by applying a negative stimulus (below the red line) when the front is passing.

Further reading on FHN on a 1D ring can be found in: Biophysical J., Vol 65 1775-1787 1993 by C.F. Starmer et al. and Physica D Vol 70 321-341 1994 by J. Starobin and Y.I. Zilberter and C.F. Starmer.