Adrenaline is produced by the adrenal glands in times of fear or stress. It targets vital organs, increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles. Preparing the body for 'flight or fight'. Adrenaline is not controlled by negative feedback.

When adrenaline is released into the bloodstream it creates multiple effects:

1. increases breathing rate, heart rate (therefore blood flow) and blood pressure
2. conversion of glycogen to glucose in liver cells, increasing blood glucose

These effects result in more glucose being delivered to the muscles and more energy being released by respiration in the muscles.

The effects of adrenaline allow the body to prepare for action in situations where a quick response may be needed.