The heart
Cambridge A-Level Biology (9700) · Unit 8: Transport in mammals · 10 flashcards
The heart is topic 8.3 in the Cambridge A-Level Biology (9700) syllabus , positioned in Unit 8 — Transport in mammals , alongside The circulatory system and Transport of oxygen and carbon dioxide. In one line: The mammalian heart has four chambers: two atria and two ventricles. Major blood vessels include the vena cava (entering right atrium), pulmonary artery (leaving right ventricle), pulmonary vein (entering left atrium), and aorta (leaving left ventricle). Coronary arteries supply the heart muscle itself with blood.
Marked as AS Level: examined at AS Level in Paper 1 (Multiple Choice), Paper 2 (AS Structured Questions) and Paper 3 (Advanced Practical Skills). The same content may also be assumed in Paper 4 (A Level Structured Questions).
The deck below contains 10 flashcards — 2 definitions and 8 key concepts — covering the precise wording mark schemes reward. Use the 2 definition cards to lock down command-word answers (define, state), then move on to the concept and calculation cards to handle explain, describe, calculate and compare questions.
Describe the external structure of the mammalian heart
The mammalian heart has four chambers: two atria and two ventricles. Major blood vessels include the vena cava (entering right atrium), pulmonary artery (leaving right ventricle), pulmonary vein (entering left atrium), and aorta (leaving left ventricle). Coronary arteries supply the heart muscle itself with blood.
What the Cambridge 9700 syllabus says
Official 2025-2027 spec · AS LevelThese are the exact learning outcomes Cambridge sets for this topic. The candidate is expected to be able to do each of these on the relevant paper.
- describe the external and internal structure of the mammalian heart
- explain the differences in the thickness of the walls of the: • atria and ventricles • left ventricle and right ventricle
- describe the cardiac cycle, with reference to the relationship between blood pressure changes during systole and diastole and the opening and closing of valves
- explain the roles of the sinoatrial node, the atrioventricular node and the Purkyne tissue in the cardiac cycle (knowledge of nervous and hormonal control is not expected)
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 9700 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Tips to avoid common mistakes in The heart
- › Define double circulation as blood passing through the heart twice for every complete circuit of the body, or mention pulmonary and systemic circuits.
- › Use 'carboxyhaemoglobin' for carbon monoxide binding and 'carbaminohaemoglobin' for carbon dioxide binding to the globin part of haemoglobin.
- › Use 'stretch' and 'recoil' for elastic fibres; 'contract' and 'relax' should only be applied to smooth muscle tissue.
- › Always use comparative adjectives like 'wider lumen', 'thicker wall', or 'more smooth muscle' when the question asks to compare structures.
- › State that semi-lunar valves only open when ventricular pressure exceeds aortic pressure; they remain closed while ventricular pressure is between atrial and aortic levels.
Describe the external structure of the mammalian heart.
The mammalian heart has four chambers: two atria and two ventricles. Major blood vessels include the vena cava (entering right atrium), pulmonary artery (leaving right ventricle), pulmonary vein (entering left atrium), and aorta (leaving left ventricle). Coronary arteries supply the heart muscle itself with blood.
Describe the internal structure of the mammalian heart.
The atria are separated from the ventricles by atrioventricular valves (tricuspid on the right, bicuspid/mitral on the left). Semilunar valves are located at the exits of the ventricles into the pulmonary artery and aorta. The septum divides the left and right sides of the heart.
Explain why the walls of the ventricles are thicker than the walls of the atria.
Ventricles pump blood to the lungs and the rest of the body, requiring more force and therefore thicker muscular walls. Atria only pump blood to the ventricles, a shorter distance, so their walls are thinner.
Explain why the left ventricle wall is thicker than the right ventricle wall.
The left ventricle pumps blood to the entire body, against higher pressure, requiring more force and a thicker wall. The right ventricle only pumps blood to the lungs, a shorter distance with lower pressure.
Describe what happens during atrial systole.
The atria contract, increasing pressure and forcing blood through the open atrioventricular valves into the ventricles. The ventricles are relaxed (diastole) at this stage.
Describe what happens during ventricular systole.
The ventricles contract, increasing pressure and forcing the atrioventricular valves to close (preventing backflow). As pressure rises further, the semilunar valves open, and blood is ejected into the pulmonary artery and aorta.
Describe what happens during diastole.
Both the atria and ventricles are relaxed. Blood flows passively from the veins into the atria and then into the ventricles through the open atrioventricular valves. The semilunar valves are closed.
Explain the role of the sinoatrial node (SAN) in the cardiac cycle.
The SAN is the heart's natural pacemaker. It initiates electrical impulses that spread across the atria, causing them to contract simultaneously. This starts each cardiac cycle.
Explain the role of the atrioventricular node (AVN) in the cardiac cycle.
The AVN receives the electrical impulse from the SAN. It delays the impulse briefly, allowing the atria to finish contracting before the ventricles contract. It then passes the impulse to the bundle of His.
Explain the role of the Purkyne tissue in the cardiac cycle.
Purkyne fibres carry the electrical impulse rapidly throughout the ventricular walls. This ensures a coordinated and simultaneous contraction of the ventricles, efficiently pumping blood out of the heart.
More topics in Unit 8 — Transport in mammals
The heart sits alongside these A-Level Biology decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
Key terms covered in this The heart deck
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