Human Nervous System (Edexcel IGCSE Biology): Revision Note

The human nervous system consists of:

• Central nervous system (CNS) – the brain and spinal cord

• Peripheral nervous system (PNS) – all of the nerves that branch out from the CNS to the rest of the body

Information is transmitted through the nervous system as electrical impulses – fast-moving electrical signals that pass along special cells called neurones

A nerve is a bundle of neurones

Nerves extends from the CNS to all areas of the body including the sense organs, allowing communication between the brain and different parts of the body

The CNS acts as the central coordinating centre processing incoming information from sense organs and coordinates the body's response

Receptors in sense organs detect stimuli (eg. light, sound, touch, temperature, chemicals)

When stimulated, receptors produce electrical impulses

These impulses travel along sensory neurones to the CNS

The CNS processes the information and sends impulses along motor neurones to effectors (muscles or glands)

Effectors carry out a response (eg. muscle contracts or gland secretes

This pathway allows rapid, automatic communication within the body

In summary:

• Stimulus → receptor → sensory neurone → CNS → motor neurone → effector → response