14.1 Mammalian Nervous System

2026 Syllabus Objectives

By the end of this topic, you should be able to:

  1. State that the nervous system (brain, spinal cord and nerves) coordinates and regulates body functions
  2. Describe the mammalian nervous system in terms of the CNS (brain and spinal cord) and PNS (nerves outside the brain and spinal cord)
  3. Identify sensory, relay and motor neurones on diagrams
  4. State that electrical impulses travel along neurones
  5. Describe simple reflex arcs in terms of receptor, sensory neurone, relay neurone, motor neurone and effector
  6. Describe a reflex action as a rapid and automatic response to a stimulus
  7. Describe a synapse as a junction between two neurones
  8. Describe the structure of a synapse, including vesicles, neurotransmitter molecules, the synaptic gap and receptor proteins
  9. Describe the events at a synapse step by step
  10. State that synapses ensure impulses travel in one direction only

Main Content

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1. The Role of the Nervous System

Your body is constantly receiving information from the world around you — sounds, temperature, pain, light — and it needs to respond to all of it. The nervous system is the body's communication network. It coordinates (organises) and regulates (controls) all body functions.

The nervous system is made up of three main parts:

  • The brain
  • The spinal cord
  • Nerves (which run throughout your entire body)

Together, these allow you to sense what is happening around you and respond to it quickly and accurately.

2. The Two Divisions of the Nervous System

The mammalian nervous system is divided into two main parts:

(a) Central Nervous System (CNS)

The CNS consists of the brain and the spinal cord.

  • The brain is found inside the skull and is the main control centre. It processes all the information coming in and decides on a response.
  • The spinal cord is a long bundle of nerve tissue running down your back, protected by the spine (backbone). It connects the brain to the rest of the body and also handles some fast responses on its own (more on this in the reflex arc section).

Think of the CNS as the headquarters of the entire system.

(b) Peripheral Nervous System (PNS)

The PNS consists of all the nerves found outside the brain and spinal cord.

These nerves branch out from the spinal cord and brain and reach every part of your body — your fingers, toes, organs, skin, and muscles.

📌 Important distinction: A neurone is a single nerve cell. A nerve is a bundle of many neurones bundled together — like a cable made of many wires.

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