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Action Potential Experiments

Click the links below 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 that you start with the first link, on the Sodium Theory**.  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 they received the Nobel Prize for their efforts.

Note:  Instructions for running videos are below the links.

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Background information: The Sodium Theory

Set up experiments outside axon

Conduct experiments outside axon

Set up experiments inside axon

Conduct experiments inside axon

Set up voltage clamp experiments

Conduct voltage clamp experiment #1 (normal sodium)

Conduct voltage clamp experiment #2 (sodium-free)

Conduct voltage clamp experiment #3 (low sodium)

Patch clamp experiments

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Note:  The links above are screen capture videos of the Action Potential Experiments computer simulation.  These videos were created because the simulation no longer works on any version of the Windows operating system more recent than Windows XP.   Use the Table of Contents (TOC) in place of buttons that appear on the screen, since these buttons only work on the actual simulation, which is still available for downloading††.  There is no sound track, so make sure to read the text on each screen.

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.

The easiest way to start and stop the video is to hit the space bar repeatedly, rather than use the video controller above.

†† The original Action Potential Experiments simulation was published by the BioQUEST Curriculum Consortium, and is still available from this link at the BioQUEST site (assuming that you still have access to Windows XP, as the simulation will not run on later versions of the Windows operating system).

**If you can use the actual simulation, we recommend that you still use this web-based video version for the Sodium Theory explanation, as there is a formatting error in the actual simulation related to the plotting of Nernst potentials.  Otherwise, the simulation screens are identical to this web-based version.

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.

 

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  1. [...] new version of the Action Potential Experiments simulation is now available for users with Windows 7 or later, as well as Macs, tablets, or other [...]