The animation is instructive content for preparing lecture/lab class slides. Instructors may choose to use the interactive version in class before detailing the Hodgkin Huxley neuron simulator.
To illustrate an action potential (watch membrane voltage vs time graph on top right), press run after setting it to current clamp mode. Current clamp injects cell with current thereby causing a spike. At an undergraduate level, the instructor may directly request the student to show a spike. Varying other parameters one may notice the cell’s firing properties change.
Ask the student to write-down every step in his notebook and detail his observations.
Conduct an action potential spiking experiment by inserting a short current pulse of 1 ms duration and variable amplitude as follows:
Begin stimulation: 3 ms.
Duration: 2 ms
Amplitude: start first with a value of 0.2.
Repeat the experiment several times, lowering the amplitude stepwise down to 0.02.
Set the end of the simulation to 40 ms.
Observe each step while changing the parameters of the simulator and note down the observations in the lab record book. Now answer the following questions:
- What is the minimal amplitude necessary to excite a spike?
- Does the form of the spike vary between different runs/different stimulation amplitudes?
- Does the delay of spike initiation vary between different runs/different stimulation amplitudes?
- Why is the sodium channel faster than the potassium channel? What is the time difference between the maxima of sodium and potassium current, respectively?
HINT: Vary simulation and stimulation time to record and note the changes in channel currents.