Virtual Physiology
the unique truly simulation software

physiology and pharmacology experiments
in virtual laboratories
almost like in the real world
- Perfect for online teaching and remote learning -

Student Licenses - in Times of the Corona Virus

As our users know, we are sending, whenever requested, additional time-limited license files for students to let them install the programs on their own computers for experimentation at home.
This may become particularly helpful when the corona virus does not allow coming together in regular practical courses.
Please note that also each institute which wants to check the potential value of our virtual laboratories can get such time-limited licenses (e.g. for 2 months) that can be forwarded to their students. Just send a short note to braun (at), including the name and address of your institution.

The Virtual Laboratories:
The Virtual Physiology programs are going far beyond conventional teaching tools, offering realistically appearing, fully equipped laboratories on the computer screen for free experimentation. All stimulation and recording devices are freely adjustable. Mathematical algorithms guarantee for the appropriate reactions of the preparations in all situations, also considering their physiological diversity.

SimHeart and SimVessel feature physiological and pharmacological experi-ments with the isolated, perfused heart in the Langendorff-setup and with isolated smooth muscle strips of blood vessels (aorta) and the stomach (antrum) to examine the muscle contractions after application of physiolo-gical transmitters (Acetylcholine), hormones (Adrenaline) and diverse drugs like the competitive receptor antagonists (Atropine, Phentolamine, Propranolol) and non-competitive modulators of Ca2+-currents and Ca2+-concentrations (Verapamil, g-Strophantin). An additional “Drug Laboratory” can be used practicing the correct preparation of the requested dilutions.

SimMuscle and SimNerv offer highly realistic experimental set-ups on the computer screen to record contractions of the frog’s gastrocnemic muscle (e.g. single twitches vs. tetanic contractions, muscle fatigue, curves of isometric and isotonic maxima) or compound action potentials from the frog’s sciatic nerve (dependence on electrode positions, refractory period, anode break potentials, etc.), respectively.
SimNeuron additionally allows performing widely used voltage- and current-clamp experiments in an easy to overlook lab design for recordings of current-voltage curves (reversal potentials etc.) or the threshold of action potential generation and its dependencies on stimulus strength and duration – also under application of TTX or TEA.
Didactic Aspects:
Although the virtual laboratories have originally been considered as minor substitutes of experi­ments with animal preparations, it turned out that the virtual labs can have major didactic advantages:
- The students are doing the experiments without negative emotions from the killing of an animal and without the fear that they need to kill one more animal if they are making a mistake that destroys the preparation.
- Only in the virtual laboratories the students feel free to explore the reaction of the preparation on their own, including unconventional stimulation protocols.
- The students have the possibility studying the reactions of the virtual preparations without any time pressure - also on their computers at home.
- Technically more challenging experiments like voltage- and patch-clamp recordings, that are unfeasible to be physically carried out in students’ introductory courses, can be realized in silico with a user-friendly interface.
  • October 5-6, 2018:

    Virtual Physiology Presentation and Workshop at the "Physiology Education Symposium", Universidad de los Andes, Bogota, Columbia.

  • September 8-14, 2018:

    Presentation of Virtual Physiology based simulations at "Neural Coding 2018" in Torina, Italy.

  • November 20, 2017:

    Summary of the Virtual Physiology updates

  • June 24, 2017:

    Virtual Physiology on exhibition at Berlin's "Lange Nacht der Wissenschaften" Poster

  • June 8-10, 2017:

    Symposium on "Life Science Research and Education" with several talk about Virtual Physiology (Program Flyer).

  • June 10, 2016:

    Virtual Physiology on exhibition at "Campus Marburg", Germany. s. Poster

  • March 3-5, 2016:

    SimHeart and SimVessel on exhibition at the Annual Meeting of the German Physiological Society (DPG). Lübeck, Germany.
    s. Poster

  • February 12, 2016:

    Heart and smooth muscle videos are now available (preliminary versions).

  • December 15, 2015:

    Recent progress of the Virtual Physiology teaching tools including corrections and extensions.

  • September 20-23, 2015:

    Virtual Physiology on exhibition at the 16th Annual Congress of EUSAAT, Linz, Austria. s. Poster

  • June 25, 2015:

    Comenius Award 2015 for SimHeart.
    Report from Sept. 1st, 2015 (in German)

  • June 13, 2015:

    Virtual Physiology on exhibition at Berlin's "Lange Nacht der Wissenschaften" Poster

  • May 24-June 15, 2015:

    Conference and lecture tour through China (Hans A. Braun) with Virtual Physiology presentations at Beihang University, Beijing, Lanzhou University of Technology, Hong Kong Baptist University and ICCN 2015 in Sanya.

  • May 22, 2015:

    Virtual Physiology new updates. Take a look on the corrections and extensions

  • March 18-21, 2015:

    Virtual Physiology on Exhibition at the Meeting of the German Neuroscience Society (NWG). Göttingen, Germany

  • March 5-7, 2015:

    Exhibition at the Annual Meeting of the German Physiological Society (DPG). Magdeburg, Germany.

  • February 20, 2015:

    Vocational training of teachers (NWG Lehrerfortbildung) with the Virtual Physiology Serie at the Physiological Institute, Univ. of Marburg. (Program)

  • January 30, 2015:

    SimNeuron 2.3.0 now with selectable features (pre-settings).

  • December 02, 2014:

    SimVessel 2.0 now available.

  • November 15-19, 2014:

    SfN Neuroscience Meeting in Washington DC ( the Virtual Physiology on exhibition with a poster (Theme H, Poster 025.04SA/VV21) and with demos at the booth of Thomas Recording (both no 2023, see also

  • September 30, 2014:

    SimVessel soon available. Take a look on the new design.

  • August 24-28, 2014:

    Virtual Physiology on exhibition at the 9th World Congress on Alternatives and Animal Use in the Life Sciences in Prag (

  • August 20, 2014:

    New versions of SimNerv 2.2.1, SimNeuron 2.2.1 and SimMuscle 2.2.1 are now available.

  • April 07, 2014:

    SimNeuron 2.2.0: New Features.

    SimHeart 2.2: Adjustment of the Verapamil and Digitalis algorithms.

  • March 13-15, 2014:

    Virtual Physiology at the 93rd German Physiological Society Meeting in Mainz ( (Poster P273).

  • March 09, 2014:

    SimNeuron with new Features for practical courses.

  • March 09, 2014:

    SimHeart upgrade is now available. Demo Versions can be downloaded.

  • November 09-13, 2013:

    SfN Neuroscience Meeting in San Diego ( the Virtual Physiology on exhibition with a poster (Theme H, Poster 021.04) and with demos at the booth of Thomas Recording (both no 1929, see also

  • October 07, 2013:

    SimHeart Demo Version is now available.

  • June 06, 2013:

    Demo Version of SimNerv can be downloaded.

  • January 29, 2013:

    Demo Versions of SimNeuron and SimMuscle are now available for download.

  • December 20, 2012:

    MacFrog congratulates KingFrog on the occasion of the 200th anniversary of the first release of Grimm Brothers folktales in Marburg, Dec. 20, 1812

  • Programs

    running on all Windows platforms,
    from Win XP to Win 10, 32 bit as well as 64 bit versions
    SimHeart and SimVessel also include .swf files to run on MacOS
    (see Technical Specifications)

    problems with Win 10?
    a) concerning hidden task bars of the Virtual Physiology programs in the full screen mode
    b) concerning strange sound effects (only in very recent Win 10 versions appearing).


    offers a virtual laboratory for recordings of heart contractions in the Langendorff set-up
    in response on the most relevant transmitters and drugs,
    including a drug laboratory for the adjustment of the appropriate solutions.

    Featured experiments:

    Effects of Adrenaline and Acetylcholine on frequency and amplitude of heart contractions
    (inotroph and chronotroph effects), effects of competitive receptor blockers Propranolol and Atropine,
    adrenaline dose-response curve and its shift by the ß-blocker Propranolol (competitive inhibition),
    comparison with non-competitive inhibition by the Ca2+-channel blocker Verapamil,
    strengthening of the contractions by the heart-glycoside g-Strophantine,
    induction and treatment of arrhythmias and heart blocks in systole and diastole.
    for details see Tutorial and Protocol form
    download a fully functioning DEMO Version


    SimVessel offers a virtual laboratory for the examination of smooth muscle contractions of vessels and the intestine.
    The experiments can be done with muscle stripes, placed in an organ bath to which physiologically relevant signal substances and widely used drugs can be added. Preparing the appropriate dilutions can be trained, as in SimHeart, in a drug laboratory.

    Featured experiments:

    Comparison of phasic and tonic smooth muscle contractions.
    Illustrating the effects of muscle stretching (Bayliss effect)
    Demonstrating opposite reactions of vessels and intestine on Adrenaline and Acetylcholine.
    Examining the effects of the cholinergic receptor antagonist Atropine.
    Comparing the effects of adrenergic α- and β-receptor antagonists (Phentolamine and Propranolol).
    Illustrating the effects of the Ca2+-channel blocker Verapamil.
    Recording of dose-response curves of Adrenaline and Acetylcholine.
    Demonstrating alterations of dose-response curves by competitive and non-competitive inhibitors.
    see Tutorial (preliminary version)
    Protocol form in preparation

    download a fully functioning DEMO Version


    offers a fully equipped, realistically appearing laboratory on the computer screen to perform classical experiments with isolated nerve-muscle preparations of the frog. All stimulation and recording parameters of the virtual devices are freely adjustable. Mathematical algorithms guarantee for the appropriated reactions of the virtual muscle, also considering the biological diversity of the preparations.

    The virtual “SimMuscle” laboratory contains two nerve-muscle preparations and all the apparatus that you will need for experimentation in a simplified but quite realistic form.

    When entering the lab you first need to switch on all the devices (POWER buttons). Then drag one of two already prepared nerve-muscle preparations from the Petri-dish to hang it in the suspension apparatus. This includes a mechano-electrical converter transforming changes of either the muscle force or muscle length, selectable by a toggle switch, into an electric potential. You can pre-stretch the muscle hanging one or more weights in the loop at which the muscle is fixed.

    Muscle contractions are induced by current pulses delivered from a stimulation apparatus to the electrodes on which the nerve is placed. Stimuli as well as muscle contractions are displayed on a dual beam storage oscilloscope, appropriately displayed with accordingly adjusted voltage amplification and time base (via the rotary switches) and zero lines. Single or double pulses as well as trains of stimuli of selectable amplitude and intervals can be applied.

    The example shows muscle contractions, here changes of the muscle length, in response to different trains of voltage pulses inducing isolated twitches, incomplete and complete tetanic contractions depending on the intervals in which the pulses are applied.

    Featured experiments:

    Single twitches and their stimulus dependencies (recruitement of motor units),
    superposition of single twitches, tetanic contractions, resting tension curves (pre-stretching),
    curves of isometric and isotonic maxima, muscle fatigue.
    for details see Tutorial and Protocol form
    For your own experiments you can download
    a fully functioning DEMO Version


    offers a fully equipped, realistically appearing laboratory on the computer screen
    to perform classical experiments of compound action potential recordings
    from isolated preparations of the frog’s sciatic nerve.
    All stimulation and recording parameters of the virtual devices are freely adjustable. Mathematical algorithms guarantee for the appropriated reactions of the virtual nerve, also considering the biological diversity of the preparations.

    In the “SimNerv” laboratory you will find a stimulator, an oscilloscope, a recording chamber and a Petri dish with two already prepared nerves.

    For your measurements take one of the nerves by mouse click out of the Petri-dish and place it on the electrodes in the recording chamber. The position of the electrodes can be changed and the temperature of the recording chamber can be adjusted. You can set a nerve ligature (fully reversible) using the thread.

    The stimulator delivers voltage pulses to the stimulation electrodes. The stimulus is simultaneously displayed at channel 1 of the oscilloscope via a separate cable..AMPLITUDE and DURATION of the stimulus pulses can be adjusted as well as the DELAY between the onsets of two successive stimuli when TWIN pulses shall be applied (MODE). The POLARITY switch allows to invert the direction of the current flow, INVERT corresponds to an exchange of the stimulus electrode positions.

    The simple double-beam storage oscilloscope displays the stimulus pulse (channel 1), simultaneously with the compound action potential (CAP, channel 2) measured as the potential difference between the two recording electrodes by means of a differential amplifier. The sensitivity of both oscilloscope channels (mV/DIV) as well as their common time-base (ms/DIV) can be adjusted via the rotary switches.

    Featured experiments:

    Stimulus-response curve: recruitment of nerve fibres on increasing stimulus amplitudes
    Strength-duration curve, rheobase, chronaxy: the impact of stimulus duration
    Refractory period and anode break potentials: physiological and clinical relevance of Na+-channel inactivation:
    Conduction velocity and the effect of temperature changes
    Recordings of bi- and mono-phasic action potentials using reversible nerve ligatures,
    Demonstrating the clinically most relevant impact of appropriate electrode positions,
    Understanding the difference between intra- and extracellular recordings.
    for details see Tutorial and Protocol form
    For your own experiments you can download
    a fully functioning DEMO Version


    virtual laboratories for voltage- and current-clamp experiments in an easy to overlook lab design

    + towards a better understanding of the relations between ion currents and action potential generation,
    + including a neuron editor showing the full set of the neuron parameters.

    Featured experiments:

    Determine the threshold of action potential generation in the current-clamp lab.
    Examine the effects of amplitude and duration of the current stimulus. Induction of a series of action potentials of different frequencies. Comparison of action potentials with local potentials and purely passive potential changes. Understanding the effects of the Na-channel blocker TTX and K+-channel blocker TEA. Display and explain the alterations of ionic conductances and currents during an action potential.

    Recordings of ion currents in the voltage-clamp lab with and without RC compensation.
    Application of the Na+-channel blocker TTX and K+-channel blocker TEA. Estimation of the activation (and inactivation) time constants. Determining the reversal potentials of Na+- and K+-currents. (tail currents). Constructing current-voltage (I-V) curves and calculation of the voltage dependencies of ion channel activation.

    for details see Tutorial and Protocol form
    download a fully functioning DEMO Version

    For the experts:

    Use the Neuron Editor to examine the effects of different membrane parameters on the neuron’s sensitivity, e.g. with alterations of voltage- and time-dependencies of ion current activation and inactivation, leak conductances, ion concentrations, etc.

    Examine how a neuron at constant resting potential can be transferred into a pacemaker neuron.


    In fully licensed versions there is the possibility to select to which specific features of the program the students shall have access. This can be done in so-called pre-settings window which you can open from the labs via the SETTINGS button in the switch bank. In demo versions the pre-settings are fixed with most functions enabled.