Structure & Function (AQA GCSE Biology): Revision Note

Nervous system: Basics

• The nervous system enables humans to detect change in the environment and to coordinate their behaviour in response

• The human nervous system consists of:

  • the central nervous system (CNS) - the brain and spinal cord

  • the peripheral nervous system (PNS) – all of the nerves in the body

• Information is sent through the nervous system as electrical impulses that pass along nerve cells known as neurones

• A bundle of neurones is known as a nerve

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Adaptations of the nervous system

• The features of the nervous system allow it to carry out its role effectively; examples include:

  • specialised cell structure

    • long axon

    • dendrites

    • myelin sheath

  • gaps between neurones

    • gaps known as synapses ensure transmission of impulses in one direction only

  • reflex arcs

    • Reflex arcs bypass the conscious brain, speeding up transmission of essential impulses

Structure of the nervous system

• Receptors detect stimuli in the environment

• Information from receptors passes along cells (neurones) as electrical impulses to the central nervous system (CNS)

• The CNS comprises the brain and spinal cord

• The CNS is the coordinator between receptors and effectors, such as muscles contracting or glands secreting hormones

• The pathway through the nervous system is:

stimulus → receptor → coordinator → effector → response