NERVOUS SYSTEM

• Functions of the nervous system

  • To collect, process and respond to information in the environment. 
  • To co-ordinate the working of different organs and cells in the body 
• The nervous system is subdivided into the ...


  ... central nervous system (CNS) and the peripheral nervous system (PNS) 
• Central nervous system (CNS)

  The brain is the centre of all conscious awareness. The outer layer of the brain (the cerebral cortex) is highly developed in humans and is what distinguishes our higher mental functions from those of animals. The brain is divided into 2 hemispheres. 

  The spinal cord is an extension of the brain. It is responsible for reflex actions and receives messages to send to the brain. 
• Peripheral nervous system (PNS)


  The PNS transmits messages via neurons (nerve cells) and is subdivided into the autonomic nervous system (ANS) and the somatic nervous system (SNS)
• Autonomic nervous system (ANS)


  The ANS controls vital functions e.g. breathing, heart rate, digestion, sexual arousal and stress responses (smooth muscles such as lungs, heart, stomach, sexual organs). It transmits information to and from internal bodily functions and is automatic/involuntary.
• The ANS is subdivided into ... 


  ... sympathetic nervous system and the parasympathetic nervous system
• Parasympathetic nervous system (body at rest)

  • Eyes - constricts pupils
  • Heart - beats slower
  • Lungs - constricts airways
  • Digestion - stimulates digestion
  • Muscles - reduces blood flow to skeletal msucles
• Sympathetic nervous system (emergency)

  • Eyes - dilates pupils
  • Heart - beats faster and stronger
  • Lungs - relaxes airways for deeper breathing
  • Digestion - inhibits digestion
  • Muscles - increases blood flow to skeletal muscles