Luo-Rudy I Model for Ventricular Cells
one-dimensional cable/ring

This applet simulates the propagation of action potentials in a cable or ring geometry as selected using the Luo-Rudy 1model. The length of the cable or ring can be varied between 0.4 cm and 26 cm. Initiation by a stimulus, propagation, and complex dynamics such as discordant alternans can be studied.

To use the applet, press the Start button. Initiate an action potential either by pressing the Apply S1 button or by clicking inside the plot. The strength, duration, length, and position of the stimulus can be set. The simulation can be paused with the Stop button and resumed using the simulation and the simulation will resume by using the Continue button. Click inside the plot to initiate more activations. The location of each activation corresponds to the location on the x-axis and the magnitude of the activation corresponds to the value on the y-axis. To make the simulation run faster or slower, use the Simulation Speed slider. To return the membrane potential of all cells to the rest value, click Reset. To adjust the size of the cable or ring, use the Cable Length slider. Use the drop-down list to select Cable or Ring geometry. The membrane voltage or other variables can be plotted by checking their boxes in the list. The list box in the bottom right corner is used to choose either the original Luo-Rudy I (LR) model or the what is commonly known as the Modified Luo-Rudy I (MLR) model, whose calcium dynamics are twice as fast with consequent action potential duration and wavelength shortening.

Things to try:

  • Click the Start button and then the Apply S1 button to generate an action potential propagating to the right. As the wave front propagates, enlarge the cable to about 21 cm. When the wave front is close to the right boundary, click the Stop button and use the list box in the lower left corner to change the cable to a ring, then click the Continue button. This allows the wave to reenter, and after a few rotations around the ring it will be a steady wave with a fixed wavelength. Decrease the ring size slowly, and observe the formation of discordant alternans at a length of 9.74 cm.
  • Repeat as above, but use the MLR-I settings and and find the lengths at which alternans appear.
  • Repeat as above, but change the sodium, potassium, and/or calcium conductances and find the length at which alternans appear.
  • Reset using the Reset button and study the threshold for excitation as a function of the stimulus parameters (strength, duration, and length) as well as the sodium and potassium conductances.
  • Induce multiple waves by clicking inside the window with the mouse. Each time the mouse is clicked, a voltage stimulus proportional to the height of the mouse position within the simulation window is added to the voltage at the location of the mouse along the cable. Try to induce a single reentrant wave along a ring.

    For more information about the Luo-Rudy Imodel, see the Luo-Rudy I applet for one cell.