AQA GCSE Biology – [UNIT 5]The Human Nervous System – Revision Notes

AQA GCSE
The Human Nervous System
Contents
Structure & Functions
The Reflec Arc
The Brain
The Eye
Control
Study Notes Of Body

, Structure & Function
Your notes

Nervous System: Basics
The human nervous system consists of:
Central nervous system (CNS) – the brain and spinal cord
Peripheral nervous system (PNS) – all of the nerves in the body
The nervous system enables humans to react to their surroundings and to coordinate
their behaviour
Information is sent through the nervous system as electrical impulses – electrical signals
that pass along nerve cells known as neurones
A bundle of neurones is known as a nerve

Adaptations of the nervous system
Neurones have a cell body (where the nucleus and main organelles are found) and
cytoplasmic extensions from this body called axons and dendrites
Some human neurones have axons over a metre in length (but only 1 - 4 micrometres
wide)
This is far more efficient than having multiple neurones to convey information from the
CNS to effectors – less time is wasted transferring electrical impulses from one cell to
another
The axon is insulated by a fatty myelin sheath with small uninsulated sections along it
(called nodes) which the impulse jumps along




© 2026 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 2

, Your notes




The human nervous system is comprised of the CNS and the PNS

Structure of the Nervous System

© 2026 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 3