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

It is worth learning this list of effects of adrenaline as it is a fairly common exam question and can be worth several easy marks.

The Hormone Adrenaline (Cambridge O Level Biology)