14.4 - Adrenaline

Adrenaline and the fight-or-flight response

• Adrenaline is a hormone released by the adrenal glands, which sit just above the kidneys.
• It's released in response to a stressful, dangerous, or exciting situation - for example extreme sports (skydiving, bungee jumping), the start of a race or a test, and emergencies.
• When the brain detects fear or stress, it sends nerve impulses to the adrenal glands, which respond by secreting adrenaline into the blood.
• This happens automatically and quickly, readying the body for the fight-or-flight response - preparing either to stand its ground against a threat or to run away from it.

Adrenaline brings about several changes that prepare the body for sudden physical effort

• Increases heart rate - The heart beats faster.
• Increases breathing rate - Air is moved in and out of the lungs more quickly.
• Widens the pupils - Their diameter increases.

Together these changes ready the body to react to the threat.