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Adrenaline is produced by the adrenal glands on top of the kidneys and prepares the body for fight or flight. Free notes and 13 questions answered.
Adrenaline: The Fight or Flight Hormone is part of Hormonal coordination in humans in GCSE AQA Higher Biology.
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GCSE AQA Higher
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Adrenaline is produced by the adrenal glands on top of the kidneys and prepares the body for fight or flight. Free notes and 13 questions answered.
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Use this lesson to stay inside Hormonal coordination in humans while connecting the detail back to the wider Homeostasis and response topic.
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.
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.
The fight or flight response evolved when our ancestors faced life-or-death situations daily. Imagine encountering a predator — you need to either fight it or run away. Both options require maximum physical performance.
Adrenaline gives you superpowers for a few minutes: increased strength, faster reflexes, and heightened awareness. Stories of people lifting cars off trapped victims? That's adrenaline at work.
But there's a trade-off. Non-essential functions shut down temporarily — digestion slows, immune responses reduce, and growth processes pause. Your body prioritises immediate survival over long-term maintenance.
Here's the issue: your body can't tell the difference between a charging lion and an upcoming exam. Both trigger the same adrenaline response, but running away from your maths test isn't exactly helpful.
Chronic stress keeps adrenaline levels elevated, which can lead to problems: high blood pressure, difficulty sleeping, and digestive issues. The system designed to save your life occasionally can become problematic in modern society.
Worked example: Worked Example: Applying Adrenaline: The Fight or Flight Hormone
Use this method to answer an exam-style question about when danger strikes.
Answer: A complete response links mechanism, evidence, and conclusion for adrenaline: the fight or flight hormone.
Exam depth extension: In adrenaline: the fight or flight hormone, connect when danger strikes to meet your body's alarm system using clear cause-and-effect statements. When you explain biological processes, include what changes, why it changes, and the consequence for cells, organisms, or populations. If calculations appear, show each step, include units, and end with a sentence that interprets the result in biological context.
For 6-mark questions about hormones, use this structure: define the hormone, explain where it's produced, describe its effects on the body, and link these effects to survival advantage.
Published by Revise Right. Use the official specification reference to check the requirements for your course. Content updated: 2026-03-20.
Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.
The fight or flight response is the body's automatic survival response to danger, caused by adrenaline, that prepares it to fight or run away. Heart rate and breathing increase, glucose is released, and non-essential functions such as digestion, immune responses and growth pause temporarily.
Adrenaline prepares the body for 'fight or flight'. It increases heart rate, increases breathing rate and widens airways, makes the liver release stored glucose, and redirects blood to the muscles, boosting the delivery of oxygen and glucose to the brain and muscles.
Adrenaline is produced by the adrenal glands, which sit like small caps on top of the kidneys, in times of fear or stress. It is not made by the heart; it travels to the heart and other organs in the blood.
Adrenaline increases heart rate, from about 70 beats per minute to over 100, to pump more blood, and so more oxygen and glucose, to the muscles and brain. Muscles need this extra oxygen and fuel for action in a fight or flight situation.
Chronic stress keeps adrenaline levels elevated, which can lead to high blood pressure, difficulty sleeping and digestive issues. The body cannot tell the difference between a charging lion and an upcoming exam, so both trigger the same adrenaline response.
Adrenaline makes the liver release stored glucose into the blood, giving muscles instant fuel for action. This is part of the fight or flight response, which also increases heart rate and breathing rate.
Adrenaline increases breathing rate and widens the airways, so more oxygen enters the bloodstream. This, together with a faster heart rate, boosts oxygen delivery to the brain and muscles for fight or flight.
Adrenaline makes blood vessels supplying muscles dilate (widen) while those supplying the digestive system constrict. Blood is redirected to where it is needed most for fight or flight.
Adrenaline is not made by the heart; it is made by the adrenal glands, which sit like small caps on top of the kidneys. It travels to the heart in the blood, where its effects are felt.
The fight or flight response evolved because ancestors faced life-or-death situations, such as meeting a predator, where they needed to fight or run away with maximum physical performance. Adrenaline gives increased strength, faster reflexes and heightened awareness for a few minutes.
When adrenaline is released, non-essential functions shut down temporarily: digestion slows, immune responses reduce and growth processes pause. The body prioritises immediate survival over long-term maintenance.
When the brain detects danger, it sends a signal down the spinal cord to the adrenal glands, and within seconds they pump adrenaline into the bloodstream. Adrenaline is produced in times of fear or stress.
An exam can trigger adrenaline because the body cannot tell the difference between a charging lion and an upcoming exam; both trigger the same response. Chronic stress keeps adrenaline levels raised, which can cause high blood pressure, difficulty sleeping and digestive issues.