Explain what happens to the blood pressure and blood flow in the heart during one complete heartbeat.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
The heart contracts and relaxes in a cycle called the cardiac cycle. During this cycle, blood is pumped from the atria into the ventricles and then out into the arteries.
Model answer (4 marks)
The atria contract, raising atrial pressure and forcing blood into the ventricles.
The ventricles then contract, raising ventricular pressure.
When ventricular pressure exceeds atrial pressure, the atrioventricular valves close and blood is pumped out of the ventricles.
Blood is forced into the pulmonary artery (right ventricle) or aorta (left ventricle), increasing arterial pressure and flow.
The ventricles then contract, raising ventricular pressure.
When ventricular pressure exceeds atrial pressure, the atrioventricular valves close and blood is pumped out of the ventricles.
Blood is forced into the pulmonary artery (right ventricle) or aorta (left ventricle), increasing arterial pressure and flow.
Examiner tips
- Use the sequence atria→ventricles→arteries to show the cycle. Show that pressure rises in each chamber before blood is forced out. Mention the valves (AV valves close, semilunar valves open).
Common mistakes
- Confusing the order of contraction (ventricles before atria). Failing to state that pressure rises before blood is forced out. Omitting the distinction between pulmonary artery and aorta.
Mark scheme (4 marks)
- The atria contract, increasing pressure in the atria
- Blood is pushed/forced from the atria into the ventricles
- The ventricles contract, increasing pressure in the ventricles
- Blood is forced out of the ventricles into the arteries (pulmonary artery / aorta)
Key terms in this question
Related
- All Eduqas GCSE Biology revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →