The Hormone Adrenaline (Cambridge (CIE) O Level Biology): Revision Note

The Hormone Adrenaline

• Adrenaline is known as the 'fight or flight' hormone as it is produced in situations where the body may be in danger

  • Flight = remove oneself rapidly from a dangerous situation eg. run away

  • Fight = if flight is not possible, resort to physical combat to overcome danger

• It causes a range of different things to happen in the body, all designed to prepare it for movement (i.e. fight or flight)

• These include: 

  • Increasing blood glucose concentration to deliver more important glucose to muscle cells for increased respiration

  • Increasing pulse rate and breathing rate so glucose and oxygen can be delivered to muscle cells, and carbon dioxide taken away, from muscles cells more quickly

  • Diverting blood flow towards muscles and away from non-essential parts of the body such as the alimentary canal; again to ensure the reactants of respiration are as available as possible

  • Dilating pupils to allow as much light as possible to reach the retina so more information can be sent to the brain

• Examples of situations where these effects may occur are:

  • Being faced with danger

  • An adventurous activity e.g. riding a roller coaster

  • Extreme sport e.g. skydiving or bungee jumping

  • Risky behaviour/activity e.g. parkour

  • A scary incident e.g. a car accident