Fiducia TogetherThe nervous system
How signals travel, and why a reflex is faster than a decision.
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.
What it is
The nervous system carries electrical impulses along neurones. A reflex arc runs stimulus → receptor → sensory neurone → relay neurone in the CNS → motor neurone → effector → response, bypassing conscious thought.
Where it applies
GCSE biology and combined science.
How it works
Reflexes are fast because they do not go via the brain's decision-making — the relay happens in the spinal cord. That speed is protective.
A synapse is the gap between neurones, crossed by a chemical neurotransmitter, which is slower than the electrical impulse along the neurone.
How to use it in your work
Learn the reflex arc as a sequence and write it in order. Marks are per stage.
Explain synaptic transmission as chemical diffusion across a gap — that word 'diffusion' is a mark.
Distinguish the nervous system (fast, short-lived, electrical) from the hormonal system (slower, longer-lasting, chemical). That comparison is a standard question.
Where to get help
Your teacher, your board's specification for the depth required at your tier, and Bitesize for the diagrams.
Revise this with a song
These are ours. We write revision songs because a lot of people remember a tune when they cannot remember a page, and because revising out loud in the kitchen beats staring at a highlighter.
- The Biology Song The GCSE biology specification, set to music.
Where to read more
Last reviewed 2026-08-28 by Fiducia Together · Next review due 2027-08-28
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.