This online version of the ‘Action Potential Experiments’ consists of screencast videos of a computer simulation originally published by the BioQUEST Curriculum Consortium. Although the actual simulation no longer runs on modern operating systems, 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.
Be sure to read the instructions for running videos, found below the links. The first link in each line includes a video with table of contents and works on computers and tablets, but may not work on smartphones. The second link in each line does not have a table of contents but the videos will be visible on smartphones.
*Background information: The Sodium Theory … phone version
Set up experiments outside axon … phone version
Conduct experiments outside axon … phone version
Set up experiments inside axon … phone version
Conduct experiments inside axon … phone version
Set up voltage clamp experiments … phone version
Conduct voltage clamp exp. #1 (normal Na) … phone version
Conduct voltage clamp exp. #2 (Na-free) … phone version
Conduct voltage clamp exp. #3 (low Na) … phone version
Patch clamp experiments … phone version
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. 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 (see below). 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, since the rollover feature may not work.
You can start and stop the video via your space bar, or via the video control.
Development of the original simulation was supported by a grant from the National Science Foundation (DUE 9254089). Opinions expressed are those of the author, and not necessarily those of the National Science Foundation. Contact mark.s.bergland@uwrf.edu for more information. Copyright 1995 and 2013, University of Wisconsin -River Falls.