Cardiac Cycle & Wiggers Diagram Lab
Drive the heart through atrial systole, ventricular systole and diastole, watch the valves open and close, and read a real Wiggers-style pressure graph.
Change heart rate, contractility and preload/afterload and watch the four chambers and valves move through one heartbeat. Use the ¼× slow-motion and step buttons below the stage to inspect each phase, and read the Wiggers-style pressure graph on the right.
About the Cardiac Cycle & Wiggers Diagram Lab
Free cardiac cycle & wiggers diagram lab. Drive the heart through atrial systole, ventricular systole and diastole, watch the valves open and close, and read a real Wiggers-style pressure graph. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for biology, the cardiac cycle & wiggers diagram lab runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Drive the heart through atrial systole, ventricular systole and diastole, watch the valves open and close, and read a real Wiggers-style pressure graph. Use it to explore biology ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Cardiac Cycle & Wiggers Diagram Lab
- Use the controls to change Heart rate, Contractility (drives stroke volume), Preload (venous filling), Afterload (arterial resistance), Activity preset. The simulation reacts instantly.
- Pick an option such as Resting, Walking, Exercise to switch modes or load an example.
- Press "Check my heart", "Check athlete heart", "Reset to defaults", "📄 Lab Report" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Switch to the Exercise preset and watch cardiac output climb.
- Raise afterload and see stroke volume fall even though heart rate is unchanged.
- Use the ¼× slow-motion button to watch exactly when each valve opens and closes.
- Try the exercise challenge: push cardiac output over 12 L/min while keeping systolic pressure under 160 mmHg.
Key ideas you can learn
- Cardiac output = heart rate × stroke volume.
- The AV valves close when ventricular pressure exceeds atrial pressure; the semilunar valves open when it exceeds arterial pressure.
- More venous filling (preload) raises stroke volume (Frank-Starling law); more arterial resistance (afterload) lowers it.
- A Wiggers diagram lines up atrial, ventricular and aortic pressure across one heartbeat.
Where this is used in the real world
Cardiologists read pressure-volume relationships like this to diagnose valve disease and heart failure, and exercise physiologists use cardiac output to judge fitness.
Who is this simulation for?
Biology students and teachers who want to explore living systems, populations and genetics interactively and safely.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
What is cardiac output?
The volume of blood the heart pumps per minute: heart rate multiplied by stroke volume.
Why does the aortic pressure trace show a small notch (dicrotic notch)?
It marks the aortic valve snapping shut once ventricular pressure falls below aortic pressure, briefly bouncing the pressure.
Is the Cardiac Cycle & Wiggers Diagram Lab free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Cardiac Cycle & Wiggers Diagram Lab work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.