📚 Nervous System Revision for GCSE AQA Biology | GCSE AQA 生物：神经系统 考点精讲
The nervous system is a rapid communication network that allows humans and other animals to detect stimuli, process information, and coordinate responses. Understanding its structure and function is essential for GCSE AQA Biology, covering everything from simple reflex arcs to the complexities of the brain and eye.
神经系统是一个快速的通信网络，使人类和其他动物能够检测刺激、处理信息并协调反应。理解其结构和功能对 GCSE AQA 生物学至关重要，涵盖从简单反射弧到大脑和眼睛的复杂性。
In this revision guide, you will find key points presented in English and Chinese, aligned with the AQA specification. Each section breaks down the topic into manageable chunks, helping you master the neurone, synapse, reflex actions, brain areas, and the eye’s focusing mechanism.
在本复习指南中，你将看到以英文和中文呈现的关键考点，与 AQA 大纲一致。每个部分将主题分解成易于掌握的小块，帮助你掌握神经元、突触、反射作用、大脑区域以及眼睛的聚焦机制。
1. Overview of the Nervous System | 神经系统概述
The nervous system enables organisms to react to their surroundings and coordinate their behaviour. It is made up of the central nervous system (CNS) – the brain and spinal cord – and a network of nerves running throughout the body.
神经系统使生物体能够对周围环境作出反应并协调行为。它由中枢神经系统（CNS）——脑和脊髓——以及遍布全身的神经网络组成。
Information flows in one general direction: from receptors to the CNS, and then from the CNS to effectors. The signals are called nerve impulses, which are electrical in nature and travel extremely fast along specialised cells called neurones.
信息通常按一个方向流动：从感受器到中枢神经系统，再从中枢神经系统到效应器。这些信号被称为神经冲动，本质上是电信号，沿着称为神经元的特殊细胞极快地传递。
2. Receptors and Effectors | 感受器与效应器
Receptors are specialised cells that detect changes in the environment, known as stimuli. Examples include light receptors in the eyes, sound receptors in the ears, touch receptors in the skin, and chemical receptors on the tongue and in the nose.
感受器是检测环境变化（即刺激）的特化细胞。例子包括眼睛中的光感受器、耳朵中的声音感受器、皮肤中的触觉感受器，以及舌头和鼻子中的化学感受器。
Effectors are parts of the body that bring about a response to a stimulus. Muscles contract to cause movement, and glands secrete hormones or other substances. The nervous system coordinates exactly which effectors should act and when.
效应器是身体中对刺激产生反应的部分。肌肉收缩引起运动，腺体分泌激素或其他物质。神经系统精确地协调哪些效应器应该作用以及何时作用。
3. Structure of Neurones | 神经元的结构
A typical neurone has a cell body containing a nucleus and most of the cytoplasm. From the cell body, many short branches called dendrites extend outwards; these receive impulses from other neurones or directly from receptors.
一个典型的神经元有一个包含细胞核和大部分细胞质的细胞体。从细胞体伸出许多称为树突的短分支；它们接收来自其他神经元或直接来自感受器的冲动。
The axon is a long fibre that carries the impulse away from the cell body towards other neurones or effectors. In many neurones, the axon is covered by a fatty myelin sheath, which insulates the fibre and speeds up impulse transmission.
轴突是一条长纤维，将冲动从细胞体传向其他神经元或效应器。许多神经元的轴突被脂质的髓鞘包裹，它起绝缘作用并加快冲动传递速度。
4. Sensory, Relay and Motor Neurones | 感觉、中间与运动神经元
There are three main types of neurones in the nervous system, each with a distinct role. Sensory neurones carry impulses from receptors to the CNS. Their cell bodies are located outside the spinal cord in structures called ganglia.
神经系统中有三种主要类型的神经元，各自扮演不同角色。感觉神经元将冲动从感受器传到中枢神经系统。它们的细胞体位于脊髓外的神经节结构中。
Relay neurones (interneurones) are found entirely within the CNS. They connect sensory neurones to motor neurones and process information. Motor neurones carry impulses from the CNS out to effectors such as muscles or glands.
中间神经元（联络神经元）完全位于中枢神经系统内。它们将感觉神经元与运动神经元连接起来并处理信息。运动神经元将冲动从中枢神经系统传送到效应器，如肌肉或腺体。
5. Synapses and Neurotransmitters | 突触与神经递质
A synapse is a tiny gap between the end of one neurone and the beginning of another. When an electrical impulse reaches the end of a neurone, it triggers the release of chemical messengers called neurotransmitters from vesicles.
突触是一个神经元末端与另一个神经元起始处之间的微小间隙。当电冲动到达神经元末端时，它会触发囊泡释放化学信使——神经递质。
The neurotransmitter diffuses across the synapse and binds to specific receptor molecules on the membrane of the next neurone. This binding can stimulate a new electrical impulse in the second neurone, allowing the signal to continue.
神经递质通过突触扩散，并与下一个神经元膜上的特异性受体分子结合。这种结合可以刺激第二个神经元产生新的电冲动，从而使信号继续传递。
Synapses ensure that impulses travel in one direction only and can filter out low-level signals. Many drugs and toxins affect the nervous system by altering synaptic transmission.
突触确保冲动只沿一个方向传递，并能过滤微弱信号。许多药物和毒素通过改变突触传递来影响神经系统。
6. The Reflex Arc | 反射弧
A reflex is a rapid, automatic response to a stimulus that does not involve conscious thought. It is a protective mechanism that minimises harm, such as quickly pulling your hand away from a hot surface.
反射是对刺激的一种快速、自动的反应，不涉及意识思维。它是一种保护机制，能减少伤害，例如迅速将手从热表面上移开。
The pathway of a reflex arc follows: stimulus → receptor → sensory neurone → relay neurone (in the spinal cord or brain stem) → motor neurone → effector → response. In spinal reflexes, the relay neurone connects directly within the spinal cord, bypassing the brain.
反射弧的通路为：刺激 → 感受器 → 感觉神经元 → 中间神经元（位于脊髓或脑干） → 运动神经元 → 效应器 → 反应。在脊髓反射中，中间神经元在脊髓内直接连接，绕过大脑。
The synapse between the sensory and relay neurone is a key point where transmission can be slowed or modified, but the overall reflex is still extremely fast because the signal does not travel all the way to the brain.
感觉神经元与中间神经元之间的突触是传递可能被减慢或修饰的关键点，但总体反射仍然极快，因为信号不需要一路传到大脑。
7. The Central Nervous System (CNS) | 中枢神经系统
The CNS consists of the brain and the spinal cord. The spinal cord is a column of nervous tissue protected by the vertebrae; it coordinates many reflex actions and carries impulses between the brain and peripheral nerves.
中枢神经系统由脑和脊髓组成。脊髓是受椎骨保护的神经组织柱；它协调许多反射动作，并在脑与周围神经之间传递冲动。
The brain is the body’s control centre, responsible for processing sensory information, initiating voluntary movements, memory, consciousness, and regulating vital functions such as breathing and heart rate.
脑是身体的控制中心，负责处理感觉信息、发起随意运动、记忆、意识，以及调节呼吸和心率等重要功能。
8. The Brain: Structure and Functions | 大脑的结构与功能
For GCSE, you need to know the roles of three key regions. The cerebral cortex (the outer part of the cerebrum) is responsible for conscious thought, intelligence, memory, language and voluntary movement.
GCSE 考试要求了解三个关键区域的功能。大脑皮层（大脑的外层部分）负责意识思维、智力、记忆、语言和随意运动。
The cerebellum sits underneath the cerebrum and controls balance, posture and the fine coordination of muscle movements. The medulla (medulla oblongata) is in the brain stem and controls unconscious activities like breathing rate, heart rate and blood pressure.
小脑位于大脑下方，控制平衡、姿势以及精细的肌肉协调动作。延髓位于脑干，控制无意识活动，如呼吸频率、心率和血压。
Scientists study the brain using several methods: observing patients who have suffered brain damage, electrically stimulating different areas during surgery, and using MRI (magnetic resonance imaging) scans to see active brain regions.
科学家通过多种方法研究大脑：观察脑损伤患者、在手术中电刺激不同区域，以及使用 MRI（磁共振成像）扫描观察活跃的脑区。
9. The Eye: Anatomy and Accommodation | 眼睛的结构与调视
The eye is a sensory organ that detects light. Light enters through the cornea, a transparent curved layer that starts the focusing process. It then passes through the pupil, whose size is adjusted by the iris to control the amount of light entering.
眼睛是检测光的感觉器官。光线通过角膜进入，这是一层透明的弯曲层，开始聚焦过程。然后光线穿过瞳孔，虹膜调节瞳孔大小以控制进入的光量。
The lens further refracts the light, and fine focusing occurs on the retina, which contains light-sensitive receptor cells: rods (for dim light) and cones (for colour perception). The optic nerve carries impulses from the retina to the brain.
晶状体进一步折射光线，精确聚焦在视网膜上，视网膜包含感光受体细胞：视杆细胞（用于弱光）和视锥细胞（用于色觉）。视神经从视网膜传递冲动到大脑。
Accommodation is the process by which the lens changes shape to focus on objects at different distances. To view a near object, the ciliary muscles contract, the suspensory ligaments loosen, and the lens becomes fatter and more convex, increasing its refractive power.
调视是晶状体改变形状以聚焦不同距离物体的过程。看近处物体时，睫状肌收缩，悬韧带松弛，晶状体变得更凸更厚，增加折射力。
To focus on a distant object, the ciliary muscles relax, the suspensory ligaments tighten, pulling the lens into a thinner, flatter shape. This reduces the bending of light rays so that they focus precisely on the retina.
对准远处物体时，睫状肌舒张，悬韧带拉紧，将晶状体拉成较薄较平的形状。这减少了光线的折射，使光线精确聚焦在视网膜上。
10. Defects of Vision | 视力缺陷
Myopia, or short-sightedness, occurs when distant objects appear blurred while near vision is clear. This happens because the eyeball is too long or the lens curves too strongly, causing light rays to focus in front of the retina.
近视（或称短视）发生时，远处物体看起来模糊而近处视力清晰。这是因为眼球过长或晶状体曲率过大，导致光线聚焦在视网膜前方。
Myopia is corrected by placing a diverging (concave) lens in front of the eye, which spreads out the light rays slightly before they enter the eye, shifting the focus back onto the retina.
近视通过在眼睛前放置发散（凹）透镜来矫正，它在光线进入眼睛前略微将它们散开，使焦点后移到视网膜上。
Hyperopia, or long-sightedness, means near objects are blurred while distant vision is clear. It is usually caused by the eyeball being too short or the lens being too flat, so light rays focus behind the retina.
远视（或称长视）意味着近处物体模糊而远处视力清晰。通常是由于眼球过短或晶状体过于扁平，光线聚焦在视网膜后方。
Hyperopia is corrected using a converging (convex) lens, which brings the rays together more strongly, focusing them onto the retina. Alternative treatments for both defects include contact lenses, laser eye surgery, and lens replacement.
远视通过使用会聚（凸）透镜矫正，它使光线更强地会聚，聚焦于视网膜上。两种缺陷的替代治疗包括隐形眼镜、激光眼科手术和晶状体置换。
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