The nervous system

• Functions of the nervous system

  • The nervous system is a specialised network of cells in the human body and is our primary internal communication system
  • It is based on electrical and chemical signals, whereas the endocrine system is based on hormones
  • To collect, process and respond to information in the environment
  • To coordinate the working of different organs and cells in the body
• The central nervous system (CNS)

  • The CNS consists of the brain and spinal cord
  • The brain controls conscious awareness and has a cerebral cortex (3mm thick), found only in mammals
  • The human brain is highly developed, enabling higher mental functions than other animals
  • The spinal cord is an extension of the brain, transmitting signals and linking nerves to the PNS, as well as controlling reflex actions, like withdrawing from heat
  • Some animals, like jellyfish and sea sponges, do not have a brain
• Peripheral nervous system (PNS)

  • The PNS transmits messages via millions of neurons to and from the CNS
  • The PNS is divided into:
  • Autonomic nervous system (ANS) governs vital functions in the body such as breathing, heart rate, digestion, sexual arousal and stress responses
  • Somatic nervous system (SNS) governs muscle movement and receives information from sensory receptors