The Human Nervous System

The nervous system detects stimuli, which helps us react and adapt to changes in our environment, It consists of:

  • Central nervous system (CNS) – The spinal cord and the brain
  • Peripheral nervous system (PNS) – The part of the nervous system outside the central nervous system. It carries information to and from the central nervous system.


Neurones (also called nerve cells) are specialised cells which have adapted to carry electrical impulses.

  • A nerve is a cluster of neurons

Axons have a long and thin structure, which is insulated by the fatty myelin sheath. Also containing sections that are not insulated, called nodes.

The axons carry messages around the body that are received by many extensions called dendrites. This means that neurones are connected to each other by a network, allowing for easy communication.

Receptors detect stimuli and send electrical impulses along neurones to the central nervous system (which is the coordination centre). Then electrical impulses are sent along neurones to effectors, which produce a response.

  • Effectors are just parts of the body that produce a response, for example, muscles (which contract) or glands (which secrete substances).

So the path through the nervous system is:

Stimulus → receptor → coordinator → effector → response