B5 - Homeostasis & Response.

• What is homeostasis?


  • To maintain a stable internal environment
  • Regulation of conditions inside body in response to changes (internal & external changes)
• Automatic control system. 


  • Includes nervous and hormonal communication systems
  • Maintains body temperature
  • Maintains blood glucose level
  • Maintains water content
• What is negative feedback?


  1. Counteracts change

  2. Brings level of something (e.g. water, glucose) back to normal when it gets too high or too low
• What is a stimulus?


  Change in environment
• Homeostasis process


  1. Receptor detects a stimulus level that is too high/low

  2. Communication centre receives and processes information & organises response.

  3. Effector produces response which counteracts change and restores optimum level (increases/decreases.
• What are Neurones? Neurones transmit information very quickly to and from the brain
• What is a Synapase?

  • Connection between two neurones
  • Chemicals set off an electrical signal in the next neurone
• Reflexes


  • They can reduce the chances of being injured
  • They don't require a decision from the brain
• Bright light shines in eyes


  Pupils automatically get smaller
• Getting a shock

  Body releases adrenaline automatically
• Reflex arcs go through the central nervous system
• What are reflexes? - Reflexes are rapid, automatic responses to certain stimuli.