IGCSE生物考试难点解析

马上就要迎来IGCSE和A-Level的大考了，在这里，Leon老师给大家带来了IG生物中的难点干货分享——心脏作用以及相关答题技巧。在这个知识点的学习中学生通常遇到的问题是：心脏供血的生理过程比较复杂，

课本上给出的东西比较散乱，不容易记忆，

因此在这里Leon老师会帮助大家总结出较好的关键词去回答问题，这样就可以避免答案冗长却没有重点的问题，希望Leon老师总结出来的干货对大家的考试有所帮助。

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相关概念总结

一、 双循环系统及其作用：

双循环系统：

The right side of the heart collects deoxygenated blood from the body and pumps it to the lungs.右侧集中了无氧血，会进入肺部携带氧气并将二氧化碳排出体外。The left side collects oxygenated blood from the lungs and pumps it to the body.左侧则主要集中了含氧血，将会进入全身循环供给各个组织（Tissue）氧气以维持呼吸作用。This is called a double circulation system, because the blood travels through  the heart twice on one complete journey around the body。所谓双循环系统就是血液需要两次进入心脏。作用：Oxygenated blood is kept separated from deoxygenated blood and the septum（隔膜） in the heart ensures this complete separation, which will increase the respiration rate.有氧血和无氧血被隔膜完全分开，双循环系统可以提高呼吸作用效率。

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心脏结构以及供血过程：

首先给大家把这些专有名词的意思以及功能作出解释：血管类Superior vena cava上腔静脉  and Inferior vena cava下腔静脉——deoxygenated blood flows back through vena cava to right atrium.无氧血通过腔静脉进入右心房。Aorta主动脉——help pump oxygenated blood to our body.主动脉输送血液至全身。Pulmonary artery肺动脉——help pump deoxygenated blood to lung for oxygen.将无氧血输送至肺部。Pulmonary vein肺静脉——Oxygenated blood flows back to left atrium含氧血通过肺静脉进入左心房。房室Atrum心房——collect deoxygenated blood from Vena cava and oxygenated blood form pulmonary vein.储存来自腔静脉的无氧血以及来自肺静脉的含氧血。Ventricle心室——pump the deoxygenated blood to lung and oxygenated blood to the body.将无氧血输送至肺部以及将含氧血输送至全身。心脏瓣膜Tricuspid valve三尖瓣——stop the blood flows back to right atrium.阻止血液回流到右心房。Mitral valve两尖瓣——stop the blood flows back to left atrium.

阻止血液回流到左心房。

Pulmonary valve肺动脉瓣——stop the blood flows back to right ventricle.阻止血液回流到右心室。

Aortic valve主动脉瓣——stop the blood flows back to left ventricle.

阻止血液回流到左心室。

心脏泵血的过程：Atrial systole(心房收缩)——The atrium contract, this forces the tricuspid and mitral valves open and blood flows into the ventricles.心房收缩，三尖瓣与两尖瓣打开血液进入心室。Ventricular systole(心室收缩)——The contraction of the ventricles makes the tricuspid and mitral valve to close and  forces the semilunar valve to open, thus this allows blood to leave the left ventricle through the aorta and right ventricle through the pulmonary artery.心室收缩三尖瓣与两尖瓣因压力而关闭阻止血液回流入心室，肺动脉瓣与主动脉瓣打开血液进入肺部以及全身。Cardiac diastole(心脏舒张) ——Atriums and ventricles relax and pressure inside the heart chambers decreases. This causes semilunar valve in the aorta and pulmonary artery close, preventing backflow of blood.心房与心室在完成动作后都会有短暂的舒张，房室内压力下降，肺动脉瓣与主动脉瓣闭合防止血液回流。 语言应用是一门技能Language learning is a skill.理解仅仅是第一步

Understanding is just the beginning.

有效练习是掌握这门技能的关键

Effective practice makes perfect.