OrganisationTopic Summary
Knowledge Organiser
Part of The Heart and Circulation · GCSE GCSE Biology revision
This topic summary covers Knowledge Organiser within The Heart and Circulation for GCSE Biology. Heart structure, cardiac cycle, blood vessels, double circulation, heart rate control, and cardiovascular health It is section 15 of 15 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 15 of 15
Practice
20 questions
Recall
25 flashcards
Knowledge Organiser
Key Terms
- Atria — upper chambers; receive returning blood
- Ventricles — lower chambers; pump blood out
- Valves — prevent backflow of blood; ensure one-directional flow
- Coronary arteries — blood vessels that supply the heart muscle itself with oxygenated blood
- Cardiac output — the volume of blood pumped by the heart per minute (= heart rate × stroke volume)
- Double circulation — blood passes through the heart twice per circuit: once through pulmonary circulation (heart → lungs → heart) and once through systemic circulation (heart → body → heart)
- Atherosclerosis — build-up of fatty deposits (atheroma) inside artery walls, narrowing the lumen and reducing blood flow
- Stent — a wire mesh tube inserted into a narrowed coronary artery to hold it open and restore blood flow
- Statins — drugs that reduce blood cholesterol levels, slowing the build-up of fatty deposits in arteries
Must-Know Facts
- Blood flow: Vena cava → right atrium → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium → left ventricle → aorta
- Left ventricle wall is thicker than right — pumps blood to the entire body at higher pressure; right ventricle only pumps to the nearby lungs
- Pulmonary artery carries deoxygenated blood; pulmonary veins carry oxygenated blood — the opposite of every other artery-vein pair in the body
- Arteries: thick muscular walls, high pressure, no valves (except at heart), carry blood away from heart
- Veins: thin walls, low pressure, have valves throughout, carry blood to heart
- Capillaries: walls one cell thick — allows exchange of oxygen, glucose, and carbon dioxide between blood and cells
- Cardiac output (ml/min) = heart rate (beats/min) × stroke volume (ml/beat); resting adult ≈ 70 × 70 = 4,900 ml/min
- CHD mechanism: atheroma builds up in coronary artery walls → lumen narrows → less oxygen reaches heart muscle → angina (chest pain on exertion) → if artery blocked completely → heart attack (cardiac muscle cells die)
- Stents hold the artery open (physical); statins reduce cholesterol to slow further build-up (chemical) — know the difference and the limitation of each
Common Mistakes
- Pulmonary exception: Students write "arteries always carry oxygenated blood." Wrong — arteries carry blood away from the heart; the pulmonary artery carries deoxygenated blood. Always define by direction, not oxygen content.
- Left/right on heart diagrams: In standard diagrams the heart faces you — the patient's right appears on the LEFT of the diagram. The right side of the heart (deoxygenated) is drawn on your left. Always check before labelling.
- Heart muscle fed by chambers: Students write "the heart muscle gets oxygen from the blood pumping through its chambers." Wrong — the thick cardiac muscle wall cannot absorb oxygen from the blood inside the chambers. It has its own separate blood supply via the coronary arteries, which branch off the aorta.
- Missing units in cardiac output: Cardiac output = heart rate (beats/min) × stroke volume (ml/beat) = ml/min. Always show working and include units — missing units loses the mark in calculation questions.
- Confusing statins and stents: Students write "statins widen the artery." Wrong — statins reduce cholesterol to slow further fatty deposit build-up; they do not physically widen the vessel. Stents physically hold the artery open. A common 2-mark "compare" question requires these to be kept separate.
- Confusing angina and heart attack: Students use these interchangeably. Angina = chest pain during exercise when the narrowed coronary artery cannot supply enough oxygen (reversible, muscle not dead). Heart attack = complete blockage, cardiac muscle cells die (irreversible). AQA mark schemes penalise conflation of these two.
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Practice Questions for The Heart and Circulation
How many chambers does the human heart have?
Explain how the structure of an artery is related to its function.
Quick Recall Flashcards
What is systole?
When the heart contracts and pumps blood out of the ventricles
What is diastole?
When the heart relaxes and the chambers fill with blood
20 questions on The Heart and Circulation — practise free
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