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Understanding
What Stress Is
Definition
What is stress?
Stress is a natural reaction of your body and brain when you face pressure, change, or danger. In reality, stress is the body’s natural defence mechanism, activated in response to a real or perceived threat.
eXaMPLES
Examples of situations that can trigger a stress response:
A deadline or heavy workload, speaking in public, a conflict, a near accident — but also positive events like moving house, achieving something at school, or an important celebration, because your body still has to adapt, even when you're happy. Your body reacts by releasing hormones such as adrenaline and cortisol: your heart rate speeds up, your muscles tense, and your alertness increases.
fight-or-flight
The beginning of stress: your brain reacts
It’s your brain that sounds the alarm: the amygdala (in the brain) detects danger, and the hypothalamus sends the signal to the nervous system. At that moment, you may feel nervous, restless, or even scared — this is your body getting ready to react. The amygdala has detected a threat, the hypothalamus has raised the alert, and now your body enters what we call the “fight-or-flight” response — the body’s first reaction to stress.
THE KEY PLAYERS IN STRESS IN YOUR BODY
Hover your mouse over each box to discover the definition.
The amygdala
Adrenaline
WHO DOES WHAT?
Cortisol
The hypothalamus
HOW ADRENALINE SHOWS UP
Here are a few concrete examples to help you recognise how adrenaline shows up in your body depending on the situation. Click on + to read and on X to close the window.
What you feel / do
Situation
Why?
What you feel / do
Situation
Why?
Why?
What you feel / do
Situation
Adrenaline acts very quickly — it puts you into a state of alertness and immediate action.
How Cortisol Shows Up
Here are some concrete examples to help you recognise how cortisol shows up in your body, depending on the situation. Click on + to read and on X to close the window.
What you feel / do
Situation
Why?
What you feel / do
Situation
Why?
Why?
What you feel / do
Situation
Cortisol helps you stay focused and alert during demanding periods. But if it stays too high for too long, it tires both your body and your mind.
In Summary
You now know what stress is, how it starts in your brain, and how your body reacts through adrenaline and cortisol. Understanding this mechanism is the first step to no longer being surprised or overwhelmed by what you feel.
Activities to check understanding
Activities to check understanding
Activities to check understanding
Activities to check understanding
Activities to check understanding
Activities to check understanding
Activities to check understanding
Activities to check understanding
Continue
Well done!
You've completed this exploration.
Start
Situation
You’re about to speak in front of the whole class.
Situation
You’re going through a period of change (new school, moving house).
What you feel / do
You stay focused, motivated, and alert.
What you feel / do
You become alert, you freeze, your breathing gets faster.
Why?
Cortisol supports your attention, but it can create tension if the effort lasts too long.
Situation
You’re working on an important project over several days.
Why?
Adrenaline sends your body the message: “You need to defend yourself or run.”
What you feel / do
You feel restless, emotional, or have trouble sleeping.
Why?
Adrenaline helps you react instantly, without needing to think first.
What you feel / do
Your heart is racing, you’re sweating, and your hands are shaking a little.
Situation
A ball is coming towards you at full speed.
Situation
You have to manage several responsibilities at the same time.
Why?
Cortisol helps your body adapt, but it can disrupt your balance if the stress continues.
Why?
Cortisol helps you maintain your energy level and vigilance during the effort.
Why?
Adrenaline is getting your body ready to react quickly to what your brain sees as a threat — other people looking at you and what they might think of you.
What you feel / do
You’re organised, but sometimes tense or distracted.
Situation
You hear a loud noise in the middle of the night.
What you feel / do
You duck or block it without even thinking.
What Stress Is
Muriel Akahi
Created on December 8, 2025
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Transcript
Use the arrows to navigate
Understanding
What Stress Is
Definition
What is stress?
Stress is a natural reaction of your body and brain when you face pressure, change, or danger. In reality, stress is the body’s natural defence mechanism, activated in response to a real or perceived threat.
eXaMPLES
Examples of situations that can trigger a stress response:
A deadline or heavy workload, speaking in public, a conflict, a near accident — but also positive events like moving house, achieving something at school, or an important celebration, because your body still has to adapt, even when you're happy. Your body reacts by releasing hormones such as adrenaline and cortisol: your heart rate speeds up, your muscles tense, and your alertness increases.
fight-or-flight
The beginning of stress: your brain reacts
It’s your brain that sounds the alarm: the amygdala (in the brain) detects danger, and the hypothalamus sends the signal to the nervous system. At that moment, you may feel nervous, restless, or even scared — this is your body getting ready to react. The amygdala has detected a threat, the hypothalamus has raised the alert, and now your body enters what we call the “fight-or-flight” response — the body’s first reaction to stress.
THE KEY PLAYERS IN STRESS IN YOUR BODY
Hover your mouse over each box to discover the definition.
The amygdala
Adrenaline
WHO DOES WHAT?
Cortisol
The hypothalamus
HOW ADRENALINE SHOWS UP
Here are a few concrete examples to help you recognise how adrenaline shows up in your body depending on the situation. Click on + to read and on X to close the window.
What you feel / do
Situation
Why?
What you feel / do
Situation
Why?
Why?
What you feel / do
Situation
Adrenaline acts very quickly — it puts you into a state of alertness and immediate action.
How Cortisol Shows Up
Here are some concrete examples to help you recognise how cortisol shows up in your body, depending on the situation. Click on + to read and on X to close the window.
What you feel / do
Situation
Why?
What you feel / do
Situation
Why?
Why?
What you feel / do
Situation
Cortisol helps you stay focused and alert during demanding periods. But if it stays too high for too long, it tires both your body and your mind.
In Summary
You now know what stress is, how it starts in your brain, and how your body reacts through adrenaline and cortisol. Understanding this mechanism is the first step to no longer being surprised or overwhelmed by what you feel.
Activities to check understanding
Activities to check understanding
Activities to check understanding
Activities to check understanding
Activities to check understanding
Activities to check understanding
Activities to check understanding
Activities to check understanding
Continue
Well done!
You've completed this exploration.
Start
Situation
You’re about to speak in front of the whole class.
Situation
You’re going through a period of change (new school, moving house).
What you feel / do
You stay focused, motivated, and alert.
What you feel / do
You become alert, you freeze, your breathing gets faster.
Why?
Cortisol supports your attention, but it can create tension if the effort lasts too long.
Situation
You’re working on an important project over several days.
Why?
Adrenaline sends your body the message: “You need to defend yourself or run.”
What you feel / do
You feel restless, emotional, or have trouble sleeping.
Why?
Adrenaline helps you react instantly, without needing to think first.
What you feel / do
Your heart is racing, you’re sweating, and your hands are shaking a little.
Situation
A ball is coming towards you at full speed.
Situation
You have to manage several responsibilities at the same time.
Why?
Cortisol helps your body adapt, but it can disrupt your balance if the stress continues.
Why?
Cortisol helps you maintain your energy level and vigilance during the effort.
Why?
Adrenaline is getting your body ready to react quickly to what your brain sees as a threat — other people looking at you and what they might think of you.
What you feel / do
You’re organised, but sometimes tense or distracted.
Situation
You hear a loud noise in the middle of the night.
What you feel / do
You duck or block it without even thinking.