The Nervous System

• The Human Nervous System


  Body wide system of nerve cells that collects information from the world, processes this information and then takes action by directing body organs and muscles via the transmission of electro chemical messages
• Central Nervous System (CNS)

  • Responsible for complex processing
• The Brain


  • Responsible for all conscious and most unconscious processing
  • Divided into two hemispheres and has many lobes
  • Provides conscious awareness and controls behaviour and regulation of the body’s physiological processes
  • Receives information from sensory receptors (eyes, skin, ears)
  • Able to send messages to muscle glands of the body
• The Spinal Chord


  • Receives and transmits information between the brain and the rest of the body
  • Extension of the brain
  • Contains circuits of nerve cells that enable us to perform reflex actions
• Peripheral Nervous System (PNS)

  • Responsible for relaying nerve impulses from the CNS to the rest of the body and vice versa
  • Body wide network of messenger neurons
• Components of the Peripheral Nervous System

  • Sensory (afferent) neurons
  • Motor (efferent) neurons
  • Divided into SNS and ANS
• Somatic Nervous System


  • Contains nerves that carry sensory signals from the body to the CNS
  • Contains nerves that carry motor signals from the CNS to skeletal muscles
  • Associated with voluntary movement
• Autonomic Nervous System


  • Carries signals from internal organs to the CNS
  • Carries signals from the CNS to the internal organs
  • Regulates digestion and heartbeat
  • Involved in regulating the internal environment and controls involuntary automatic processes
• Sympathetic Nervous System


  • Increases bodily activities
  • Primarily involved in responses that help deal with emergencies
  • Releases noradrenaline
  • Inhibits less important bodily processes such as digestion and urination
• Parasympathetic Nervous System


  • Decreases bodily activities
  • Primarily involved in returning the body to a rest state once the emergency has passed
  • Releases acetylcholine
  • Bodily processes inhibited by the sympathetic branch are returned to normal
• Sympathetic Nervous System activation

  Causes heart rate to increase, blood pressure to increase and sweating increases
• Parasympathetic Nervous System activation


  Stimulates digestion, increases salivation and slows heart rate