📚 KS3 CIE Muscles Exam Question and Mark Scheme | KS3 CIE 肌肉考试题与评分标准
Welcome to this KS3 CIE revision guide on muscles. In this article, you will find a focused exam-style question, a full mark scheme, and clear explanations of the key ideas you need to know about how muscles work in the human body.
欢迎阅读本篇 KS3 CIE 肌肉专题复习指南。本文提供一道紧扣考点的考试型题目、完整评分标准，以及关于人体肌肉工作原理的核心知识点解析。
1. Understanding the KS3 CIE Muscles Topic | 了解 KS3 CIE 肌肉主题
At KS3, the CIE science curriculum expects you to explain how muscles bring about movement at joints. You need to link muscle action to the skeleton, tendons, and antagonistic pairs such as the biceps and triceps.
在 KS3 阶段，CIE 科学课程要求你能够解释肌肉如何在关节处引起运动。你需要把肌肉活动与骨骼、肌腱以及肱二头肌和肱三头肌等拮抗肌对联系起来。
To succeed in exam questions on muscles, you need to use precise scientific vocabulary such as contract, relax, antagonistic pair, tendon, ligament, and joint. You also need to apply these ideas to real movements such as bending and straightening the arm.
要在肌肉类考题中取得好成绩，你需要使用准确的科学词汇，如收缩、放松、拮抗肌对、肌腱、韧带和关节。你还需要把这些知识应用到屈臂、伸臂等真实运动中。
2. Key Muscle Types and Their Roles | 主要肌肉类型及其作用
Humans have three types of muscle: skeletal muscle, smooth muscle, and cardiac muscle. Skeletal muscle is attached to bones and is under voluntary control; smooth muscle is found in organs such as the intestines and blood vessels; cardiac muscle is found only in the heart.
人体有三种肌肉：骨骼肌、平滑肌和心肌。骨骼肌附着在骨骼上，受意识控制；平滑肌存在于肠道和血管等器官中；心肌只存在于心脏。
Skeletal muscle is also called striated muscle because it has a striped appearance under a microscope. It is the type of muscle you use when you run, write, or lift an object, and it is the main focus of movement questions at KS3.
骨骼肌又称横纹肌，因为它在显微镜下呈条纹状。它是你跑步、写字或提物体时使用的肌肉类型，也是 KS3 运动类题目的主要考查对象。
For movement questions, you will almost always be discussing skeletal muscle. Skeletal muscles work by contracting, which means they get shorter and thicker, pulling on bones via tendons.
在运动类题目中，你讨论的几乎总是骨骼肌。骨骼肌通过收缩工作，也就是变短、变粗，并通过肌腱牵拉骨骼。
3. Antagonistic Muscle Pairs | 拮抗肌对
Muscles can only pull; they cannot push. Therefore, to move a bone back and forth, muscles must work in pairs called antagonistic pairs. One muscle contracts while the other relaxes.
肌肉只能拉，不能推。因此，要让骨骼来回运动，肌肉必须成对工作，这种配对称为拮抗肌对。一对肌肉中，一块收缩，另一块放松。
The classic example is the upper arm. The biceps is on the front of the upper arm, and the triceps is on the back. When you bend your elbow, the biceps contracts and the triceps relaxes. When you straighten your elbow, the triceps contracts and the biceps relaxes.
最典型的例子是上臂。肱二头肌位于上臂前侧，肱三头肌位于上臂后侧。屈肘时，肱二头肌收缩，肱三头肌放松；伸肘时，肱三头肌收缩，肱二头肌放松。
Another example is the knee joint, where the hamstrings at the back of the thigh work against the quadriceps at the front. When you bend your knee, the hamstrings contract and the quadriceps relax; when you straighten it, the quadriceps contract and the hamstrings relax.
另一个例子是膝关节，大腿后侧的腘绳肌与前侧的股四头肌相互拮抗。屈膝时，腘绳肌收缩，股四头肌放松；伸膝时，股四头肌收缩，腘绳肌放松。
Examiners often ask you to name the agonist and antagonist. The agonist is the muscle that contracts to produce the movement; the antagonist is the muscle that relaxes to allow the movement.
考官经常要求你说出主动肌和拮抗肌。主动肌是收缩产生运动的肌肉；拮抗肌是放松以允许运动发生的肌肉。
4. How Muscles Produce Movement | 肌肉如何产生运动
When a skeletal muscle contracts, it pulls on a tendon. The tendon is a tough, non-elastic cord that connects muscle to bone. Because the tendon is attached across a joint, the pulling force makes the bone move around the joint.
当骨骼肌收缩时，它会牵拉肌腱。肌腱是连接肌肉和骨骼的坚韧、无弹性的索状组织。由于肌腱跨过关节附着，牵拉力使骨骼围绕关节运动。
The point where a muscle attaches to a stationary bone is called the origin. The point where it attaches to the moving bone is called the insertion. At KS3 you may not need these terms in detail, but they help explain direction of movement.
肌肉附着在固定骨上的点称为起点，附着在运动骨上的点称为止点。KS3 阶段可能不需要深入掌握这些术语，但它们有助于解释运动方向。
Bones act as levers, and joints act as pivots or fulcrums. When a muscle contracts, it supplies the effort force that moves the bone against a load, such as lifting a book in your hand.
骨骼起到杠杆的作用，关节起到支点或转轴的作用。当肌肉收缩时，它提供动力，使骨骼克服负荷而运动，比如举起手中的书本。
5. Tendons, Ligaments and Joints | 肌腱、韧带与关节
It is easy to confuse tendons and ligaments. A tendon connects muscle to bone. A ligament connects bone to bone and holds joints together. Tendons transmit pulling forces; ligaments provide stability.
肌腱和韧带很容易混淆。肌腱连接肌肉与骨骼；韧带连接骨与骨，并固定关节。肌腱传递拉力；韧带提供稳定性。
Joints are places where two or more bones meet. Movable joints, such as the elbow and knee, are surrounded by a joint capsule and contain synovial fluid that reduces friction between the bones.
关节是两块或多块骨骼相遇的地方。肘关节和膝关节等可动关节由关节囊包裹，内含滑液，可以减少骨骼之间的摩擦。
Cartilage also covers the ends of bones in a synovial joint. It acts as a smooth, shock-absorbing layer, helping the joint move without pain or damage.
软骨还覆盖在滑膜关节的骨端。它作为光滑、可吸收冲击的保护层，帮助关节无痛、无损伤地活动。
6. Muscle Cells and Energy Supply | 肌肉细胞与能量供应
Muscle cells contain many mitochondria because contraction requires a lot of energy. Energy is released by aerobic respiration, which can be summarised as:
肌肉细胞含有大量线粒体，因为收缩需要大量能量。能量通过有氧呼吸释放，可概括为：
glucose + oxygen → carbon dioxide + water + energy
葡萄糖 + 氧气 → 二氧化碳 + 水 + 能量
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