# Describe the sequence of events that causes blood to be pumped out of the heart during one heartbeat, starting from when the atria contract.

> WJEC GCSE Biology (Wales) — 1.4.2 The heart · Describe · 4 marks

## Mark scheme (4 marks)

1. The atria contract, pushing blood into the ventricles (through the atrioventricular valves).
2. The atrioventricular valves close (preventing backflow into the atria) as the ventricles begin to contract.
3. The ventricles contract, increasing pressure inside them.
4. Blood is forced out of the ventricles into the arteries (aorta / pulmonary artery), and the semilunar valves open to allow this.

## Key terms

- [atria](https://www.gradenine.co.uk/glossary/atria)
- [contract](https://www.gradenine.co.uk/glossary/contract)

## Related

- [Revision notes for WJEC GCSE Biology (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-the-sequence-of-events-that-8c52d31c) · Published by Druglandscape Ltd.