The nervous system and homeostasis

• Nervous system


  Enables humans to react to their surroundings and to coordinate their behaviour - this includes both voluntary and involuntary actions
• Nervous system responses


  1. Stimulus detected by receptors

  2. Receptor information passes along neurones to CNS as electrical impulses

  3. CNS coordinates body's response to stimulus

  4. Effectors bring about a response
• Structure of nervous system

  • Made up of central nervous system (brain and spinal cord) and a network of nerves
• Homeostasis


  Regulation of internal conditions (of a cell or whole organism) in response to internal and external changes, to maintain optimum conditions for functioning
• What homeostasis controls in the human body

  • Blood glucose concentration
  • Body temperature
  • Water levels
• Control systems of homeostasis

  • Involve receptor cells, coordination centres, and effectors
• Reflex actions


  Automatic and rapid responses of the nervous system that do not involve the conscious part of the brain
• Reflex arc structures


  • Sensory neurone, relay neurone, motor neurone, synapse
• Synapse


  Gap between neurones that allows electrical impulses to cross between them
• Factors affecting reaction time

  • Tiredness
  • Distractions
  • Caffeine
  • Alcohol
• The mechanism of homeostasis makes a good six-mark question