Guide to Using HHsim
HHsim is a graphical simulation of a
section of excitable neuronal membrane using the Hodgkin-Huxley equations. It
provides full access to the Hodgkin-Huxley parameters, membrane parameters,
stimulus parameters, and ion concentrations, and can be used for many sorts of
exercises.
Starting HHsim
If you've downloaded and installed the executable
version of HHsim for Windows, you can start HHsim via a shortcut on the desktop
or an entry in the Start menu. Or you can go to the HHsim folder and click on
the icon for hhsim.exe.
To run the Unix executable, cd to that directory and type ./hhsim to begin.
If you've downloaded just the Matlab source code, run Matlab, cd to the
directory containing the source, and type "hhsim". Note: HHsim requires Matlab
version 6 or higher.
Main Window
The main window consists of two plots. The large plot
displays membrane voltage in red and external stimuli (current pulses) in blue.
The smaller plot displays three quantites as yellow, green, and cyan lines. By
default these are the Hodgkin-Huxley variables m, h, and n, but other
information can be selected, such as currents or conductances. The yellow,
green, and cyan pulldown menus select the variables to be plotted.
Click on the purple Stim1 or Stim2 buttons to inject a
depolarizing or hyperpolarizing current stimulus. Click on the Membrane,
Channels, or Stimuli buttons to view and modify the simulation parameters.
Clicking on any of the plot lines causes an elliptical cursor to appear, and
the value of the selected variable is displayed in the cursor subpanel in the
bottom right corner of the main window. Cursor control buttons move the cursor
left or right, either by one timestep or to the next local maximum or minimum of
the graph.
The simulation runs whenever a stimulus is applied or a parameter value
is changed. It stops when the membrane voltage appears to have reached an
asymptote. If it stops too soon, click the yellow Nudge button to nudge
the simulation along for a few more time steps. Click Run (green button)
to enter continuous run mode, and Stop (red button) to leave this mode.
The Clear button clears the display and resets the time, but does not
affect any other simulation parameters. The Recall button resets the
Hodgkin-Huxley variables to a previously-stored state. Initially this is the
resting state; see the cursor control page
for information on saving state for later recall. Zoom in and Zoom
out buttons are self-explanatory.
Click here for cursor controls
The Print button outputs the plots in the main window as a
Postscript file, suitable for printing or for inclusion in other documents. The
Export button saves the plotted curves as a table in ASCII format,
readable by Microsoft Excel, Matlab (using the importdata
function), and many other programs. If the cursor is active, only that curve are
exported; otherwise all the curves are exported.
Membrane Window
The Membrane window provides for manipulation of
internal and external ion concentrations, and adjustment of a few membrane
parameters.
Channels Window
The Channels window provides access to parameters for
each of the active or passive channel types. Channels can be temporarily
disabled by clicking the associated toggle to the left of the channel name.
For passive channels the only parameter is the conductance, in micro-Siemens.
For active channels, namely the fast sodium channel, the delayed rectifier, and
a user-defined active channel, a Details button calls up another window for
accessing the channel's Hodgkin-Huxley parameters. Shown below is the window for
the fast sodium channel.
Stimuli Window
The Stimuli window controls the parameters for two
external stimuli, Stim1 and Stim2, each of which consists of either a single
current pulse or a sequence of two independently-adjustable pulses.
Drugs Window
The Drugs window allows application of any of three drugs:
TTX, which inhibits the sodium current; TEA, which inhibits the potassium
current; and pronase, which eliminates sodium channel inactivation. Any time a
drug is being applied, the Drugs button in the main window will be yellow
instead of the usual gray
Voltage Clamp Mode
HHsim starts up in "Voltage Reporting" mode. To
switch to "Voltage Clamp" mode, use the pulldown menu in the upper right portion
of the main screen.
Click here for voltage clamp controls
This work was supported in part by National Science Foundation grant
DGE-9987588. Any opinions, conclusions, or recommendations expressed herein are
those of the authors and do not necessarily reflect the views of the National
Science Foundation.
Dave TouretzkyLast
modified: Wed Nov 5 01:03:38 EST 2003