📚 6B1 The Circulatory System Exam Practice | 6B1 循环系统真题精练
This revision guide provides targeted exam practice for Topic 6B1 The Circulatory System, covering heart structure, blood vessels, double circulation, and common exam pitfalls. Each section presents a typical exam-style question or explanation with model answers, followed by Chinese translation to support bilingual learners.
本精练指南针对 6B1 循环系统专题，提供真题演练，涵盖心脏结构、血管、双循环及常见失分点等重要概念。每节先给出典型考题或讲解及标准答案，然后配以中文翻译，帮助双语学习者掌握考点。
1. Heart Anatomy – Key Labels | 心脏解剖 – 关键标注
The heart is composed of four chambers: two upper atria and two lower ventricles. The right side handles deoxygenated blood, while the left side handles oxygenated blood. The septum separates the left and right sides to prevent mixing of oxygenated and deoxygenated blood.
心脏由四个腔室组成：两个上房（心房）和两个下室（心室）。右侧处理缺氧血，左侧处理富氧血。间隔将左右两侧隔开，防止富氧血与缺氧血混合。
A typical exam question asks: ‘Label the chambers and major blood vessels on the diagram of the heart.’ (6 marks) You must be able to identify the aorta, vena cava, pulmonary artery, pulmonary vein, right atrium, right ventricle, left atrium, and left ventricle.
典型考题要求：“在下图标注心脏的腔室和主要血管。”（6分）你必须能够识别主动脉、腔静脉、肺动脉、肺静脉、右心房、右心室、左心房和左心室。
Key point: The pulmonary artery carries deoxygenated blood – the only artery that does so. The pulmonary vein carries oxygenated blood – the only vein that does so. Remembering this prevents a common labelling error.
关键点：肺动脉输送缺氧血——它是唯一输送缺氧血的动脉；肺静脉输送富氧血——它是唯一输送富氧血的静脉。牢记这一点能避免常见的标注错误。
2. The Cardiac Cycle and Heartbeat | 心动周期与心跳
The heart muscle is myogenic – it can contract without stimulation from nerves. A group of cells in the right atrium, the pacemaker (sinoatrial node), generates electrical impulses that spread across the atria, causing them to contract. After a short delay at the atrioventricular node, the impulse travels to the ventricles, which contract and force blood out of the heart.
心肌是肌源性的——无需神经刺激即可自主收缩。右心房内的一组细胞——起搏点（窦房结）——产生电冲动，电冲动传遍心房，引起心房收缩。冲动在房室结短暂延迟后传至心室，心室随即收缩，将血液泵出心脏。
Exam question: ‘Describe the events that occur during one cardiac cycle.’ (4 marks) Model answer: Atria contract (atrial systole), pushing blood into ventricles. Ventricles then contract (ventricular systole), forcing blood into arteries. Semilunar valves open; atrioventricular valves close to prevent backflow. Finally, the heart relaxes (diastole) and fills with blood.
考试题：“描述一个心动周期内发生的事件。”（4分）标准答案：心房收缩（心房收缩期），将血液推入心室。心室随后收缩（心室收缩期），将血液压入动脉。半月瓣打开；房室瓣关闭以防止血液倒流。最后心脏舒张（舒张期）并重新充盈血液。
3. Blood Vessels: Arteries, Veins and Capillaries | 动脉、静脉和毛细血管
Arteries carry blood away from the heart. They have thick muscular and elastic walls to withstand high pressure. Veins carry blood back to the heart; they have thinner walls, a wider lumen, and valves to prevent backflow. Capillaries link arteries and veins; their walls are only one cell thick to allow efficient exchange of materials by diffusion.
动脉将血液运离心脏。动脉壁厚且有肌肉和弹性组织，以承受高压。静脉将血液送回心脏；静脉壁较薄、管腔较宽，并具有瓣膜以防止倒流。毛细血管连接动脉与静脉；其管壁仅一个细胞厚，有利于通过扩散高效交换物质。
Typical question: ‘Compare the structure of an artery with that of a vein.’ (3 marks) Answer: An artery has a thicker muscular wall and a smaller lumen than a vein; it lacks valves. A vein has a thinner wall, a larger lumen, and possesses valves.
典型问题：“比较动脉与静脉的结构。”（3分）答案：动脉的肌层比静脉厚，管腔比静脉小；动脉无瓣膜。静脉壁较薄，管腔较大，且具有瓣膜。
4. Components of Blood | 血液的成分
Blood consists of plasma, red blood cells, white blood cells, and platelets. Red blood cells contain haemoglobin, which binds to oxygen for transport. White blood cells defend the body against pathogens – lymphocytes produce antibodies, while phagocytes engulf microorganisms. Platelets initiate blood clotting at wound sites. Plasma transports nutrients, carbon dioxide, hormones, and waste products.
血液由血浆、红细胞、白细胞和血小板组成。红细胞含有血红蛋白，血红蛋白能与氧结合进行运输。白细胞抵御病原体——淋巴细胞产生抗体，吞噬细胞吞噬微生物。血小板在伤口处启动凝血过程。血浆运输营养物质、二氧化碳、激素和代谢废物。
Exam question: ‘State one function of lymphocytes and one function of phagocytes.’ (2 marks) Lymphocytes produce antibodies that target specific antigens. Phagocytes engulf and digest pathogens by phagocytosis.
考试题：“说出淋巴细胞的一种功能和吞噬细胞的一种功能。”（2分）淋巴细胞产生针对特定抗原的抗体。吞噬细胞通过吞噬作用吞入并消化病原体。
5. Double Circulation Explained | 双循环详解
Mammals have a double circulatory system consisting of pulmonary circulation (heart → lungs → heart) and systemic circulation (heart → rest of the body → heart). This ensures oxygenated and deoxygenated blood are kept separate and that blood is pumped at high pressure to the body, allowing efficient oxygen delivery.
哺乳动物具有双循环系统，包括肺循环（心脏 → 肺 → 心脏）和体循环（心脏 → 身体其他部位 → 心脏）。这确保富氧血与缺氧血分离，并能将血液以较高压力泵送至全身，实现高效的氧气输送。
Question: ‘Describe the pathway of a red blood cell from the right ventricle to the left atrium.’ (3 marks) The red blood cell is pumped from the right ventricle into the pulmonary artery, travels to the lungs where it picks up oxygen, returns to the heart via the pulmonary vein, and enters the left atrium.
问题：“描述一个红细胞从右心室到左心房所经过的路径。”（3分）红细胞从右心室被泵入肺动脉，行至肺部并在此获得氧气，再通过肺静脉返回心脏，进入左心房。
6. Coronary Heart Disease and Risk Factors | 冠心病与风险因素
The coronary arteries supply oxygenated blood to the heart muscle. If they become narrowed or blocked by fatty plaques (atherosclerosis), blood flow is reduced, leading to angina or myocardial infarction (heart attack). Major risk factors include a diet high in saturated fat, smoking, lack of exercise, obesity, and genetic predisposition.
冠状动脉为心肌供应富氧血。如果冠状动脉因脂肪斑块（动脉粥样硬化）变得狭窄或堵塞，血流量减少，可导致心绞痛或心肌梗死（心脏病发作）。主要风险因素包括高饱和脂肪饮食、吸烟、缺乏运动、肥胖和遗传易感性。
Explain how a high-fat diet can lead to coronary heart disease. A diet rich in saturated fats raises blood cholesterol levels. Cholesterol is deposited in artery walls, forming atheroma plaques that narrow the lumen and reduce elasticity. This restricts blood flow and increases the risk of a clot (thrombosis) blocking the artery completely.
解释高脂饮食如何导致冠心病。富含饱和脂肪的饮食会使血液胆固醇水平升高。胆固醇沉积在动脉壁，形成粥样斑块，使管腔变窄并降低血管弹性。这会限制血流，并增加血栓完全堵塞动脉的风险。
7. Measuring Heart Rate and Pulse | 测量心率与脉搏
Pulse rate is a measure of heart beats per minute (bpm). It can be measured at the wrist or neck. During exercise, heart rate increases to deliver more oxygen to muscles and remove carbon dioxide faster. The time taken for heart rate to return to resting level after exercise – the recovery time – is an indicator of fitness.
脉率即每分钟心跳次数，可在手腕或颈部测得。运动时心率加快，以便向肌肉输送更多氧气并更快清除二氧化碳。运动后心率恢复至静息水平所需的时间——恢复时间——是衡量体能的一个指标。
Exam question: ‘A student recorded a resting pulse of 72 bpm and a pulse of 130 bpm immediately after running. Explain why the pulse rate increased.’ (3 marks) The increased pulse rate reflects the heart working harder to pump more oxygenated blood to active muscles. Carbon dioxide produced during respiration also needs to be removed quickly, and increased blood flow achieves both aims.
考试题：“一名学生记录静息脉率为72次/分，跑步后即刻脉率为130次/分。解释为什么脉率增加了。”（3分）心率加快反映心脏更努力地工作，以向活跃肌肉泵送更多的富氧血。呼吸作用产生的二氧化碳也需要迅速清除，加快的血流可同时达成这两个目的。
8. Exam Question: Explain How Valves Work | 真题：解释瓣膜如何工作
Valves in the heart and veins ensure unidirectional blood flow. The atrioventricular (AV) valves between atria and ventricles prevent backflow when ventricles contract. The semilunar valves at the exits of the pulmonary artery and aorta prevent blood returning to the ventricles after contraction. In veins, pocket valves prevent the backward flow of blood, especially when skeletal muscles squeeze the veins.
心脏和静脉中的瓣膜确保血液单向流动。心房与心室之间的房室瓣在心室收缩时防止血液倒流回心房。肺动脉和主动脉出口处的半月瓣防止心室收缩后血液倒流回心室。静脉中的口袋状瓣膜防止血液倒流，尤其是当骨骼肌挤压静脉时。
Question: ‘Explain the role of valves in the circulatory system.’ (4 marks) High-level answer: Atrioventricular valves close when ventricular pressure exceeds atrial pressure, stopping backflow into atria. Semilunar valves open when ventricular pressure exceeds artery pressure, allowing ejection, then close to prevent backflow from arteries. Vein valves ensure blood moves toward the heart despite low pressure.
问题：“解释瓣膜在循环系统中的作用。”（4分）高分答案：当心室压力超过心房压力时，房室瓣关闭，防止血液倒流回心房。当心室压力超过动脉压力时，半月瓣打开，允许血液射出，随后关闭以防止动脉血液倒流。静脉瓣确保在低压状态下血液仍能流向心脏。
9. Exam Question: Describe the Pathway of Blood | 真题：描述血液的路径
A classic extended question: ‘Describe the complete journey of a red blood cell starting from the right atrium and ending in the aorta.’ (5 marks) Right atrium → right ventricle → pulmonary artery → lungs (pulmonary capillaries) → pulmonary vein → left atrium → left ventricle → aorta. At the lungs, carbon dioxide diffuses out and oxygen diffuses in; the blood becomes oxygenated.
典型的拓展题：“描述一个红细胞从右心房出发最终到达主动脉的完整旅程。”（5分）右心房 → 右心室 → 肺动脉 → 肺（肺毛细血管）→ 肺静脉 → 左心房 → 左心室 → 主动脉。在肺部，二氧化碳扩散出，氧气扩散入；血液变为富氧血。
To gain full marks, mention the relevant valves: the tricuspid valve prevents backflow from right ventricle to right atrium; the pulmonary semilunar valve blocks return from pulmonary artery; the bicuspid (mitral) valve prevents backflow in the left side; the aortic semilunar valve stops return from aorta.
要获满分，应提及相关瓣膜：三尖瓣防止血液从右心室倒流回右心房；肺半月瓣阻止血液从肺动脉回流；二尖瓣（僧帽瓣）防止左侧倒流；主动脉半月瓣阻止血液从主动脉回流。
10. Comparison of Blood Vessels Table | 血管比较表格
The following table summarises the structural and functional differences among arteries, capillaries and veins.
以下表格总结了动脉、毛细血管和静脉在结构和功能上的差异。
| Feature | Artery | Capillary | Vein |
|---|---|---|---|
| Wall thickness | Thick, muscular, elastic | One cell thick | Thin, less muscle |
| Lumen size | Small | Extremely small | Large |
| Valves present? | No | No | Yes |
| Blood flow direction | Away from heart | From arterioles to venules | Toward heart |
| Pressure | High | Low | Very low |
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