SCIENCE · INVESTIGATE AND EXPLAIN

Separate ejected volume, fractional ejection and external work

A pressure–volume loop connects ventricular filling, pressure rise at nearly fixed volume, ejection and pressure fall at nearly fixed volume. Stroke volume is end-diastolic minus end-systolic volume. Ejection fraction divides stroke volume by end-diastolic volume, so two ventricles can have the same fraction but different absolute ejected volumes. Neither quantity alone measures myocardial energy use.

Learning outcome: Change end-diastolic volume and ejection pressure separately. Reconstruct all four loop vertices, stroke volume, fraction and both work terms. State which physiological causes of a changed loop remain unidentified.

Starting recap

Trace cardiovascular and respiratory anatomy, conserve pressure-flow and gas-content ledgers, and distinguish transport, storage, binding and feasible uptake under explicitly supplied nonclinical boundaries.

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Try

At end-diastolic volume 120 mL and ejection pressure 10 kPa, stroke volume is 80 mL and ejection fraction 2/3. Ejection work is 0.80 J, filling return 0.08 J and net loop work 0.72 J.

Open the experiment

Predict

Does zero volume change during a pressure rise imply zero cellular energy consumption?

Your prediction and reason

Experiment

Change end-diastolic volume and ejection pressure separately. Reconstruct all four loop vertices, stroke volume, fraction and both work terms. State which physiological causes of a changed loop remain unidentified.

Separate stroke volume, ejection fraction and loop work

Worked teaching model · synthetic values · Original rectangular ventricular loop: end-systolic volume 40 mL, filling pressure 1 kPa, supplied constant ejection pressure b. Net external work is enclosed area (b−1)(a−40) kPa mL; 1 kPa mL=0.001 J. Not an actual cardiac trace or myocardial efficiency estimate.

End-diastolic volume: 120 mL Ejection pressure: 10 kPa

Reset keeps your prediction, captures and practice history.

The enclosed pressure–volume area measures supplied external loop work, not metabolic energy.

Isovolumetric segments change pressure without volume work in this model. The rectangular trace simplifies actual filling/ejection curves; oxygen demand and efficiency require additional measurements.

Ordered loop vertices: filling, pressure rise, ejection, pressure fall
Ventricular volume (mL)	Pressure (kPa)
40	1
120	1
120	10
40	10
40	1

Conditional quantities; each row retains its own unit
Quantity	Value	Unit
Stroke volume	80	mL
Ejection fraction	0.6666667	fraction
Ejection pressure-volume work	0.8000000	J
Filling pressure-volume return	0.08000000	J
Net loop work	0.7200000	J

Original instructional diagrams and parameters, not individual physiological measurements, safety limits or treatment guidance.

The enclosed pressure–volume area measures supplied external loop work, not metabolic energy.

Observation to attach to a capture

Captures preserve recipes and replay their calculated results. They are synthetic model evidence, not physical measurements.

Understand

1. Trace the anatomical pathway

2. Define the mechanism and boundary

The original rectangular loop has end-systolic volume 40 mL, selectable end-diastolic volume and filling pressure 1 kPa. Ejection takes place at a separately supplied constant pressure. The rectangle deliberately simplifies the actual curved filling and ejection trajectories; changing a control specifies a new ideal loop rather than predicting a real muscle response.

Pressure times volume change has energy units. Ejection work is high pressure times stroke volume, while filling returns the low-pressure volume work in the chosen loop accounting. Net external loop work is (ejection pressure −1) times stroke volume. Because 1 kPa mL is 0.001 J, numerical multiplication without unit conversion would overstate work a thousandfold.

The vertical isovolumetric segments have no pressure–volume work because volume does not change, even though the muscle remains metabolically active. The loop does not include all myocardial internal work, basal metabolism or efficiency. Changes in preload, afterload and contractility are important physiological concepts, but this prescribed geometry alone does not isolate them from one another or establish clinical function.

3. Reconstruct the original evidence

At end-diastolic volume 120 mL and ejection pressure 10 kPa, stroke volume is 80 mL and ejection fraction 2/3. Ejection work is 0.80 J, filling return 0.08 J and net loop work 0.72 J.

4. Predict and investigate

Predict first: Does zero volume change during a pressure rise imply zero cellular energy consumption?

5. Defend a changed transport case

Apply the mechanism to a changed boundary

At end-diastolic volume 80 mL and ejection pressure 6 kPa, find stroke volume, ejection fraction and net work.

Retain the first response, units, uncertainty and any prior feedback exposure in the notebook before comparing this public explanation.

Compare a worked response

Stroke volume is 40 mL, fraction 1/2, ejection work 0.24 J and filling return 0.04 J, leaving 0.20 J. The reduced external work does not uniquely determine oxygen consumption.

6. Preserve a bounded explanation

Retain your first prediction, full units and conservation checks, an alternative mechanism and a discriminating observation in the Anatomy course workspace. These invented data are not individual physiological values. Do not perform breath-holding, forced breathing, exercise challenges, blood sampling or personal measurements. Public answer exposure does not establish independent learner or practical competence.

Supporting anatomical mechanism, checked 30 October 2026. Original models, diagrams and exercises; no clinical interpretation or treatment guidance.

Apply

Public practice checks a specific claim. It does not establish independent mastery.

At end-diastolic volume 80 mL and ejection pressure 6 kPa, find stroke volume, ejection fraction and net work.

Your explanation and limitations

Continue

Completion requires a saved prediction, at least one capture and a reflection. Presence checks do not grade your reasoning.

Skipping retains experiments and awards no mastery.

Previous: Trace circulation before inferring a valve state Next: Distinguish arterial storage from mean perfusion

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