The Nervous System | 神经系统 考点精讲

📚 The Nervous System | 神经系统 考点精讲

The nervous system is the body’s rapid communication network, detecting changes in the internal and external environment and coordinating appropriate responses. For IGCSE CCEA Biology, mastering this topic means understanding how nerve cells (neurones) transmit signals, how reflex arcs produce quick involuntary reactions, and how sense organs like the eye convert stimuli into electrical impulses. This article covers all the key points you need to know, from the structure of a neurone to the comparison of nervous and hormonal control.

神经系统是人体内快速的通讯网络，它探测体内外环境的变化，并协调合适的反应。对于IGCSE CCEA生物学考试，掌握这一主题意味着要理解神经细胞（神经元）如何传递信号、反射弧如何产生快速的不随意反应，以及像眼睛这样的感觉器官如何将刺激转化为电冲动。本文将涵盖你需要知道的所有要点，从神经元结构到神经控制与激素控制的比较。

1. Organisation of the Nervous System | 神经系统的组织

The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord, which act as the coordination and processing centres. The PNS comprises all the nerves that branch out from the CNS to the rest of the body, carrying messages to and from the CNS.

神经系统分为中枢神经系统（CNS）和周围神经系统（PNS）。中枢神经系统由脑和脊髓组成，起到协调和处理中心的作用。周围神经系统则包含从CNS发出并连接到身体其余部分的所有神经，负责将信息传入和传出CNS。

In the PNS, nerves are bundles of many neurones. The neurones that carry impulses from sense organs to the CNS are sensory neurones; those that carry impulses from the CNS to muscles or glands are motor neurones. The cell bodies of sensory neurones are located in small swellings called ganglia just outside the spinal cord.

在周围神经系统中，神经是由许多神经元组成的束。将冲动从感觉器官传送到CNS的神经元称为感觉神经元；将冲动从CNS传送到肌肉或腺体的则是运动神经元。感觉神经元的细胞体位于脊髓外称为神经节的小膨大中。

2. Structure and Types of Neurones | 神经元的结构与类型

A typical neurone has a cell body containing a nucleus, several branching dendrites that receive impulses, and a long axon that carries impulses away from the cell body. Many axons are surrounded

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