Adrenaline: The Fight or Flight Hormone Revision Notes | GCSE OCR Foundation Biology

What this lesson covers

Explore how adrenaline is produced by the adrenal glands during stress or fear, and learn how it prepares the body for 'fight or flight' by increasing h...

• Explain how adrenaline prepares the body for fight or flight responses
• Describe the role of adrenal glands in hormone production
• Analyse the effects of adrenaline on heart rate, breathing and blood flow
• Evaluate the advantages of the fight or flight response in survival situations

Key ideas to keep in view

Use this lesson to stay inside B3.2 Coordination and control - the endocrine system while connecting the detail back to the wider B3: Organism level systems topic.

• B3: Organism level systems
• B3.2 Coordination and control - the endocrine system
• GCSE OCR Foundation Biology

Lesson notes preview

Read the core explanations from Adrenaline: The Fight or Flight Hormone before testing yourself from memory.

• Picture this: you're walking alone at night when you hear footsteps behind you. Instantly, your heart pounds, your breathing quickens, and you feel a surge of energy. This isn't panic — it's your body's ancient survival system kicking in.
• This automatic response has kept humans alive for thousands of years. The chemical messenger responsible? Adrenaline — your body's emergency hormone.
• A hormone produced by the adrenal glands in times of fear or stress. It increases heart rate and boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for 'flight or fight'.
• Your adrenal glands sit like small caps on top of your kidneys. When your brain detects danger, it sends a signal down your spinal cord to these glands. Within seconds, they pump adrenaline into your bloodstream.
• Trap: Many students think adrenaline is produced by the heart because that's where you feel the effects. Actually, it's made by the adrenal glands and travels to the heart via the blood.
• When adrenaline floods your system, it triggers a coordinated response across multiple organs. Think of it as your body running through an emergency checklist:
• Heart: Rate increases from 70 beats per minute to over 100. This pumps more blood (and oxygen) to your muscles and brain.
• Lungs: Breathing rate increases and airways widen. More oxygen enters your bloodstream.
• Liver: Releases stored glucose into the blood. Your muscles need instant fuel for action.
• Blood vessels: Those supplying muscles dilate (widen) while those to the digestive system constrict. Blood gets redirected to where it's needed most.

Continue through the topic

Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.