Cardiac Cycle · Heart Dynamics
Explore one simplified cardiac cycle with ventricular volume, pressure changes, valve states and cardiac output for NCERT and NEET.
NCERT alignment: Class 11; chapter Body Fluids and Circulation. Exam practice: NEET.
Learning objectives
Students should use the live simulator to test a quantitative prediction, read measurements and explain the limits of the model. Do not rely on the animation alone: calculate the expected result before adjusting controls.
Theory, equations and interpretations
One heartbeat has several phases
Atrial systole precedes ventricular contraction; isovolumetric contraction closes both relevant left-heart valves; ventricular ejection opens the aortic valve; isovolumetric relaxation closes it; ventricular filling begins once the mitral valve opens.
Stroke volume and cardiac output
Stroke volume is blood expelled from the ventricle per beat: SV=EDV−ESV. Cardiac output is CO=SV × heart rate. Ejection fraction EF=SV/EDV×100%. These are simplified left-ventricle classroom readouts.
Important relation: SV = EDV − ESV; CO = SV × HR; EF = 100SV/EDV
Valves are pressure-driven
Mitral valve permits atrium-to-ventricle flow during ventricular filling; aortic valve permits ventricle-to-aorta flow during ejection. During both isovolumetric phases, neither valve allows net flow, so ventricular volume is constant.
Reading pressure-volume graphs
Pressure and volume change across phases of the cycle. Here the plots are conceptual, not measured Wiggers diagrams. Aortic pressure is sketched, while right-heart circulation, electrical conduction and detailed waveforms are omitted.
Practical investigations
- Measure cardiac output: Set HR=72 bpm, EDV=120 mL and ESV=50 mL; calculate SV, EF and CO and compare the displayed values.
- Valve sequence: Watch the two valve labels during isovolumetric contraction and ejection. Explain why volume remains fixed in the former.
- Change heart rate: Increase HR from 72 to 100 bpm while holding SV fixed. Compute how the idealized CO changes and state why real physiology is more complex.
- Graph the cycle: Switch between pressure and volume graphs and identify ejection, relaxation and filling periods.
Worked exam-style questions and answers
Q1. Stroke volume is
Options: A. EDV+ESV; B. EDV−ESV; C. ESV/HR; D. HR/EDV
Answer: B. SV=EDV−ESV.
Q2. If SV=70 mL and HR=70/min, cardiac output is
Options: A. 0.49 L/min; B. 4.9 L/min; C. 49 L/min; D. 70 L/min
Answer: B. CO=70×70=4900 mL/min=4.9 L/min.
Q3. During isovolumetric contraction, ventricular volume
Options: A. Increases; B. Decreases; C. Remains constant; D. Becomes zero
Answer: C. Both mitral and aortic valves are closed; there is no ejection or filling.
Q4. The aortic valve opens primarily during
Options: A. Ventricular ejection; B. Atrial systole; C. Isovolumetric relaxation; D. Early filling
Answer: A. Left-ventricular pressure overcomes aortic pressure to initiate ejection.
Q5. Ejection fraction is
Options: A. EDV/ESV; B. SV/EDV; C. SV×HR; D. ESV×HR
Answer: B. EF=SV/EDV, normally written as a percentage.
Q6. The mitral valve is open during
Options: A. Ventricular ejection; B. Isovolumetric contraction; C. Ventricular filling; D. Isovolumetric relaxation
Answer: C. Filling from left atrium to left ventricle occurs through the mitral valve.
Common misconceptions and limitations
This is a conceptual teaching model, not patient-specific physiology or a diagnostic device. Pressure waveforms and phase fractions are schematic; blood flow, electrophysiology and pathology are not clinically simulated.
All learning content is available free of charge. The simulation is a simplified educational model. Check assumptions and units before applying a result. NANDAX SimStudio is not affiliated with NCERT or examination boards.
Teacher classroom use
Ask students to form a hypothesis, vary one parameter at a time, keep a record of graph readings, explain any change and compare results with the analytic relation. The on-screen worksheet offers questions with an answer key.