This online version of the ‘Action Potential Experiments’ consists of screencast videos of a computer simulation originally published by the BioQUEST Curriculum Consortium. The videos will enable you to re-create the Nobel Prize-winning experiments of Hodgkin and Huxley, as you set up and conduct experiments to determine the nature of the mechanism responsible for nerve impulses.

We suggest starting with the first link, on the Sodium Theory, describing the nature of the action potential.  You will then be able to vary ion concentrations as you attempt to solve the puzzle that confronted Hodgkin and Huxley, using the giant axon of the squid as your experimental model.  Put yourself in the place of these investigators as they waited each morning for the fishing fleet to come in, so that they could use fresh squid axons for their experiments.  Then imagine what it must have been like in 1963 when, along with John Eccles, they received the Nobel Prize for their efforts.

Development of the original simulation was supported by a grant from the National Science Foundation (DUE 9254089). Copyright 1995-2025, University of Wisconsin -River Falls.

IMPORTANT: Be sure to read the instructions for running videos, found below the links. Also, make sure to use links in the phone version column if you are using a smart phone. (The computer / tablet version has an interactive table of contents, but the video may not be visible on a smart phone.)

Part	Computer / tablet version	Phone version	Location
1	The Sodium Theory (start here)	The Sodium Theory (start here)	YouTube (text and audio)
2	Set up experiments outside axon	Set up experiments outside axon	Case It website (text only)
3	Conduct experiments outside axon	Conduct experiments outside axon	Case It website (text only)
4	Set up experiments inside axon	Set up experiments inside axon	Case It website (text only)
5	Conduct experiments inside axon	Conduct experiments inside axon	Case It website (text only)
6	Set up voltage clamp experiments	Set up voltage clamp experiments	Case It website (text only)
7	Conduct voltage clamp exp. #1 (normal Na)	Conduct voltage clamp exp. #1 (normal Na)	Case It website (text only)
8	Conduct voltage clamp exp. #2 (Na-free)	Conduct voltage clamp exp. #2 (Na-free)	Case It website (text only)
9	Conduct voltage clamp exp. #3 (low Na)	Conduct voltage clamp exp. #3 (low Na)	Case It website (text only)
10	Patch clamp experiments	Patch clamp experiments	Case It website (text only)

Instructions:  The links above are screen capture videos of the Action Potential Experiments computer simulation, with the first link on each line including a Table of Contents (TOC). Use the TOC in place of buttons that appear in the videos, since these buttons only work on the actual simulation that is no longer available.  Except for the YouTube video on the Sodium Theory, there is no sound track, so make sure to read the text on each screen. Text will be small on phones, so use your fingers to zoom and drag to make text more legible. This will not be necessary if you use a tablet instead of a phone. There is no TOC for the phone version, so use the dragbar to move to particular spots in each video.

You can hide the TOC using the icon to the right of the video control icon (see below – at red arrow).

The TOC will disappear once the mouse cursor is off of the video screen, but clicking  the icon will make it disappear until the icon is clicked again.  If you are using an iPad or other mobile device, it may be necessary to click the icon to get the TOC to disappear. You can start and stop the video via your space bar, or via the video control.