📚 GCSE WJEC Biology: The Nervous System | GCSE WJEC 生物：神经系统 考点精讲
The nervous system is the body’s master controlling and communicating system. It uses electrical impulses to enable rapid responses to changes in the internal and external environments. For GCSE WJEC Biology, understanding the structure of neurones, the reflex arc, synaptic transmission and the effects of drugs is essential.
神经系统是人体的主要控制和通信系统。它通过电信号来对内外环境的变化做出快速反应。对于 GCSE WJEC 生物课程，掌握神经元的结构、反射弧、突触传递以及药物的影响至关重要。
1. The Nervous System: An Overview | 神经系统概览
The human nervous system is divided into two major parts: the central nervous system (CNS), which consists of the brain and spinal cord, and the peripheral nervous system (PNS), which comprises all the nerves that branch out from the CNS to the rest of the body. Its primary role is to detect stimuli, process information, and coordinate effectors to produce a response.
人体神经系统分为两个主要部分：由脑和脊髓组成的中枢神经系统（CNS），以及由从中枢向身体各处发出的所有神经构成的周围神经系统（PNS）。神经系统的主要功能是探测刺激、处理信息并协调效应器产生反应。
Compared with the endocrine system, nervous communication is extremely fast, uses electrical impulses, and has effects that are short-lived but highly specific. This makes it ideal for instantaneous reactions, such as pulling your hand away from a hot object.
与内分泌系统相比，神经通信速度极快，以电信号传递，持续时间短但特异性强。这使它非常适合于即时反应，例如手碰到烫物时迅速缩回。
2. Neurones: The Building Blocks | 神经元：基本组成单元
Neurones are specialised cells adapted to carry electrical impulses. A typical neurone has a cell body containing the nucleus, branching dendrites that receive signals, and a long axon that conducts impulses away from the cell body to other neurones or effectors. Many axons are surrounded by a myelin sheath made of Schwann cells, which insulates the fibre and speeds up impulse transmission.
神经元是特化来传导电脉冲的细胞。一个典型的神经元包含含有细胞核的细胞体、接受信号的分支树突以及将冲动从细胞体传向其他神经元或效应器的长轴突。许多轴突被由施万细胞构成的髓鞘包裹，这层绝缘层能加速冲动的传递。
The junction at the end of the axon is called the axon terminal. Here the electrical signal is converted into a chemical signal to cross a synapse to the next cell. The high degree of cellular specialisation ensures one‑way, rapid communication.
轴突末端的连接点称为轴突末梢。在此处，电信号转变为化学信号以越过突触传给下一个细胞。高度的细胞特化确保了单向、快速的通信。
3. Types of Neurones | 神经元的类型
Three types of neurones work together in a coordinated pathway: sensory, relay (or interneuron), and motor. Each has a distinct shape and location that reflect its function.
三种类型的神经元在协调的通路中协同工作：感觉神经元、中继（中间）神经元和运动神经元。它们各自的形状和位置都反映了其功能。
| Type | Structure & Location | Function |
|---|---|---|
| Sensory neurone 感觉神经元 |
Long dendrite from receptor; cell body located in a ganglion just outside the spinal cord; short axon carrying impulse into the CNS. | Carries impulses from a receptor to the CNS. |
| Relay neurone 中继神经元 |
Short dendrite and short axon; entirely within the CNS (spinal cord or brain). Many interconnections. | Connects sensory and motor neurones; processes information in reflexes. |
| Motor neurone 运动神经元 |
Cell body in the CNS; long axon running out to an effector (muscle or gland). | Carries impulses from the CNS to an effector to bring about a response. |
The differences in length and placement of cell bodies ensure a short reflex pathway and rapid protective actions. Being able to identify each neurone in a diagram is a common WJEC exam requirement.
细胞体长度和位置的差异确保了反射通路的简短和快速保护动作。在 WJEC 考试中，常常要求能够在示意图中识别每一种神经元。
4. The Nerve Impulse: How Signals Travel | 神经冲动的传导
A nerve impulse is a self-propagating wave of electrical disturbance that travels along the axon membrane. At rest, the inside of an axon is negatively charged relative to the outside; this is the resting potential, maintained by the sodium–potassium pump that moves 3 Na⁺ out for every 2 K⁺ moved in.
神经冲动是一种沿轴突膜自行传播的电扰动波。静息时，轴突内部与外部相比带负电；这称为静息电位，由钠钾泵维持，该泵每运出 3 个 Na⁺ 的同时运入 2 个 K⁺。
When a stimulus reaches the threshold, sodium ion channels open, Na⁺ flood in, and the membrane depolarises rapidly. This creates an action potential – a brief reversal of charge. Immediately afterwards, potassium ion channels open, K⁺ rush out, and the membrane repolarises. The impulse is ‘all or nothing’; its magnitude does not vary, and it jumps between the gaps in the myelin sheath (nodes of Ranvier), a process called saltatory conduction, which increases speed.
当刺激达到阈电位时，钠离子通道开放，Na⁺ 涌入，膜迅速去极化，产生动作电位——一个短暂的电性反转。之后钾离子通道开放，K⁺ 快速流出，膜复极化。冲动是“全或无”的，其幅度不变。在有髓鞘的轴突上，冲动在髓鞘间隙（郎飞结）之间跳跃传导，称为跳跃式传导，从而提高了传导速度。
5. Synapses: Junctions Between Neurones | 突触：神经元之间的连接
A synapse is the small gap between the axon terminal of one neurone and the dendrite of the next. When an action potential arrives at the presynaptic terminal, it triggers vesicles to fuse with the membrane and release neurotransmitter molecules (such as acetylcholine) into the synaptic cleft.
突触是一个神经元轴突末梢与下一个神经元树突之间的小间隙。当动作电位到达突触前末梢时，它促使囊泡与膜融合，并将神经递质分子（如乙酰胆碱）释放到突触间隙中。
The neurotransmitter diffuses across the cleft and binds to specific receptors on the postsynaptic membrane. This opens ion channels and initiates a new electrical impulse in the receiving neurone. Because receptors are only on the postsynaptic side, synapses ensure one‑way transmission. Excess neurotransmitter is rapidly broken down by enzymes (e.g., acetylcholinesterase) or reabsorbed to prevent continuous stimulation.
神经递质扩散穿过间隙，与突触后膜上的特异性受体结合，打开离子通道，在接收神经元中引发新的电冲动。由于受体仅存在于突触后侧，突触确保了单向传递。多余的神经递质会迅速被酶（如乙酰胆碱酯酶）分解或被重新吸收，以防止持续刺激。
6. Reflex Arc: A Rapid Response | 反射弧：快速反应
A reflex is an automatic, involuntary response to a stimulus that protects the body from harm. The reflex arc is the simplest nerve pathway and does not involve the conscious brain. The sequence is: stimulus → receptor → sensory neurone → relay neurone in the spinal cord → motor neurone → effector (muscle or gland).
反射是对刺激的自动、不随意反应，能保护身体免受伤害。反射弧是最简单的神经通路，不需要大脑有意识的参与。其顺序为：刺激 → 感受器 → 感觉神经元 → 脊髓中的中继神经元 → 运动神经元 → 效应器（肌肉或腺体）。
A classic example is the withdrawal reflex: touching a hot object activates heat‑pain receptors in the skin, the impulse travels to the spinal cord where it passes directly to a motor neurone, causing the biceps muscle to contract and withdraw the hand. At the same time, other interneurons inhibit the antagonist muscle (triceps) to allow smooth movement. Reflexes are rapid because the pathway is short and involves few synapses.
一个经典的例子是缩手反射：触摸热物会激活皮肤中的热痛感受器，冲动传到脊髓，在那里直接传递给运动神经元，引起肱二头肌收缩，将手缩回。同时，其他中间神经元会抑制拮抗肌（肱三头肌），使动作顺畅。反射之所以迅速，是因为通路短、涉及的突触数量少。
7. The Central Nervous System (CNS) | 中枢神经系统
The CNS is the processing centre of the body, consisting of the brain and spinal cord. The brain can be divided into several regions: the cerebrum, responsible for conscious thought, memory, and voluntary movement; the cerebellum, which coordinates balance and fine muscle control; and the medulla oblongata (brain stem), which controls vital autonomic functions like heart rate and breathing.
中枢神经系统是人体的处理中心，由脑和脊髓组成。脑可以分为几个区域：大脑负责有意识的思维、记忆和随意运动；小脑协调平衡和精细肌肉控制；延髓（脑干）控制心跳和呼吸等生命攸关的自主功能。
The spinal cord acts as a relay between the brain and the body and is also the site of integration for simple reflexes. It is protected by the vertebral column, meninges, and cerebrospinal fluid. Damage to the spinal cord can interrupt communication and cause paralysis below the injured site.
脊髓在脑和身体之间起到中继作用，也是简单反射的整合部位。它受到脊柱、脑膜和脑脊液的保护。脊髓损伤会中断通信，导致损伤部位以下的瘫痪。
8. The Peripheral Nervous System (PNS) | 周围神经系统
The PNS connects the CNS to limbs and organs. It is composed of 12 pairs of cranial nerves arising from the brain and 31 pairs of spinal nerves from the spinal cord. Functionally, it is divided into the sensory (afferent) division, which carries impulses from receptors to the CNS, and the motor (efferent) division, which carries signals from the CNS to effectors.
周围神经系统将中枢神经系统与四肢和器官连接起来。它由 12 对脑神经（发自脑）和 31 对脊神经（发自脊髓）组成。按功能可分为感觉（传入）部分，将冲动从感受器传向中枢；以及运动（传出）部分，将信号从中枢传向效应器。
The motor division can be further subdivided into the somatic nervous system, which controls voluntary skeletal muscles, and the autonomic nervous system, which regulates involuntary actions such as digestion and gland secretion. The autonomic system has two branches—sympathetic and parasympathetic—that often work antagonistically to maintain internal balance.
运动部分可进一步细分为控制随意骨骼肌的躯体神经系统，以及调节消化和腺体分泌等不随意动作的自主神经系统。自主神经系统又分为交感神经和副交感神经两支，它们常常拮抗地工作以维持内部平衡。
9. Effects of Drugs on the Nervous System | 药物对神经系统的影响
Many drugs alter synaptic transmission and can profoundly affect mood, coordination, and reaction time. Stimulants, such as caffeine and nicotine, increase the rate of nerve impulses by promoting neurotransmitter release or blocking re‑uptake, leading to heightened alertness and faster reaction times. Depressants like alcohol enhance the effect of inhibitory neurotransmitters (e.g., GABA), slowing down neural activity, impairing judgment and reflexes.
许多药物能改变突触传递，深刻影响情绪、协调能力和反应时间。兴奋剂，如咖啡因和尼古丁，通过促进神经递质释放或阻断其再摄取来加快神经冲动，从而提高警觉性并缩短反应时间。抑制剂如酒精则会增强抑制性神经递质（如 GABA）的作用，减慢神经活动，削弱判断力和反应能力。
Hallucinogens, such as LSD, interfere with serotonin pathways and distort perception. Long‑term drug misuse can lead to tolerance, where more drug is needed to achieve the same effect, and physical dependence, with withdrawal symptoms upon stopping. Understanding synaptic mechanisms helps explain why certain drugs are dangerous and addictive.
致幻剂（如 LSD）会干扰血清素通路并扭曲感知。长期滥用药物会导致耐受性（需要更多剂量才能达到相同效果）和身体依赖（停药时出现戒断症状）。理解突触机制有助于解释为什么某些药物危险且易成瘾。
10. Required Practical: Investigating Reaction Time | 规定的实验：探究反应时间
In the WJEC GCSE Biology course, students must be able to measure reaction time using the ruler drop test. One person holds a ruler just above the open hand of the test subject and releases it without warning. The subject catches the ruler as quickly as possible; the distance the ruler falls before being caught is measured and converted to reaction time using a calibration table or the equation t = √(2d/g).
在 WJEC GCSE 生物课程中，学生必须能够使用尺子下落测试来测定反应时间。一人将尺子悬在受试者张开的手上方，并在无预兆的情况下释放。受试者尽可能快地抓住尺子；记录抓住前尺子下落的距离，并利用对照表或公式 t = √(2d/g) 转换为反应时间。
The investigation can explore the effect of factors such as caffeine, practice, or distraction. The independent variable is the condition tested (e.g., caffeinated vs non‑caffeinated drink), the dependent variable is the reaction time, and controlled variables include the height of drop, the ruler size, and the distance between fingers and ruler. Repeats are essential to ensure reliability, and outliers should be noted.
该探究可以考察诸如咖啡因、练习或分心等因素的影响。自变量是所测试的条件（如含咖啡因饮料与不含咖啡因饮料），因变量是反应时间，控制变量包括释放高度、尺子尺寸以及手指与尺子的间距。重复实验对于保障可靠性至关重要，并应记录异常值。
11. Homeostasis and Nervous Coordination | 稳态与神经协调
Homeostasis is the maintenance of a constant internal environment. The nervous system works together with the endocrine system to detect changes and trigger corrective mechanisms. For example, if blood glucose rises, pancreatic receptors detect this and the brain can stimulate insulin release via the vagus nerve. However, most homeostatic responses involve purely hormonal pathways.
稳态是指维持内环境恒定的状态。神经系统与内分泌系统共同探测变化并启动纠正机制。例如，血糖升高时，胰腺感受器检测到变化，大脑可通过迷走神经刺激胰岛素分泌。不过，大多数稳态反应是通过纯激素途径进行的。
The nervous system is especially vital in rapid homeostatic adjustments like shivering or sweating when body temperature deviates from 37 °C. Thermoreceptors in the skin and hypothalamus send impulses to effectors such as muscles and sweat glands. Thus, nervous and endocrine systems provide an integrated control network that keeps the body functioning optimally.
神经系统在快速的稳态调整中尤为关键，例如体温偏离 37 °C 时的发抖或出汗。皮肤和下丘脑的温度感受器向肌肉和汗腺等效应器发送冲动。因此，神经与内分泌系统构成了一个整合的控制网络，保持身体最佳运作。
12. Key Points to Remember | 关键要点总结
To succeed in the WJEC GCSE Biology examination on the nervous system, focus on the sequence of neurones in a reflex arc, the mechanism of synaptic transmission, the role of neurotransmitters and the all‑or‑nothing nature of nerve impulses. Be able to label and compare sensory, relay and motor neurones, and explain how myelination speeds up conduction.
要在 WJEC GCSE 生物考试中成功应对神经系统部分，应重点关注反射弧中神经元的顺序、突触传递的机制、神经递质的作用以及神经冲动的“全或无”特性。要能够标记并比较感觉、中继和运动神经元，并解释髓鞘化如何加速传导。
Additionally, understand the effect of common drugs on synaptic activity and be prepared to describe the ruler drop practical, including variables and reliability. Clear, precise use of scientific terminology and data analysis skills will be rewarded.
此外，要了解常见药物对突触活动的影响，并准备好描述尺子下落实验，包括变量及可靠性。清晰、准确地使用科学术语和数据分析技能将获得加分。
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