OCR GCSE Biology 2026 – 400 Free Practice Questions to Pass the Exam

Adrenaline, also known as epinephrine, plays a crucial role in the body’s response to stress or danger, which is often referred to as the "fight or flight" response. When adrenaline is released, it activates a range of physiological processes that are aimed at preparing the body to respond quickly to a perceived threat.

One of the primary effects of adrenaline is to increase the supply of oxygen and glucose to vital organs, especially muscles and the brain, which are essential during times of stress or physical activity. The hormone accomplishes this by stimulating increased heart rate and dilating air passages to improve oxygen intake. Additionally, it promotes the breakdown of glycogen in the liver to release glucose into the bloodstream, thus providing a quick source of energy.

This shift in focus to oxygen and glucose supply is crucial for rapid energy production and improved physical performance, making it the correct and relevant answer in the context of what adrenaline activates in the body.