Adrenaline - GCSE Biology Definition

Adrenaline, also known as epinephrine, is a hormone produced by the adrenal glands, which sit above the kidneys. It plays a crucial role in the 'fight or flight' response, a physiological reaction to stress or danger. When a threat is detected, adrenaline is released into the bloodstream. This increases heart rate, widens air passages in the lungs, and triggers the liver to convert glycogen into glucose, providing more energy for muscles. Adrenaline helps prepare the body for quick action and is an example of how the body responds to external stimuli and maintains homeostasis.