The stress hormones: Adrenaline


By Line Bloch, 14. June 2016

Welcome to part 3 of a series of 5

This series takes you through the physics of stress, and how to prevent it. Start here – and dig deeper into each element.

The impact on our ‘fight-or-flight’ response

The most important hormones when it comes to stress are – as you perhaps already know – Adrenaline and Cortisol.

But what do they do and how do they actually work? Are they dangerous and why?

Adrenaline is the major player in your body’s ‘fight-or-flight’ response to dangerous situations. You know of an adrenaline kick, and you know how it feels: sweaty palms, fast heart beat, cold skin, blushing, a bit of shaking, but overall a sharp focus and heightened awareness.

The production and release of adrenaline is triggered by the sympathetic part of your autonomic nervous system as a response to dangerous situations.


The specific effects in the body that create a feeling of adrenaline rush is:

  • Increased glucose production by the liver. This releases readily available energy to the large muscles, to enable you to get away fast or hit hard.
  • Increased dilation of lung bronchioles. To get more oxygen fast into the blood.
  • Increased heart rate, so that the glucose and oxygen can reach the muscles and brain fast.
  • Increased dilation of blood vessels to ease the passage of the blood and get the blood faster out in the body. This is why you blush: the small blood vessels in the skin holds more blood.
  • Increased pupil dilation to be able to see more clear.


  • Decreased saliva production.
  • Decreased gastrointestinal and bladder activity.

Last two are there to save energy and fluids. You don’t need spit when you run or fight, and you have not time finding a bathroom.

Effect on Amygdala

Amygdala is part of the system triggering release of adrenaline, but there is a feedback loop, where adrenaline boosts the amygdala-driven emotional learning, and also induces more fear and aggressiveness.

Read more on amygdala here.

Effect on hippocampus

Adrenaline also hit hippocampus, and stimulates the creation of lasting memories of the event.

Read more on hippocampus here.

The good thing about adrenaline – apart from the vital role it plays in our survival in dangerous situations, is that it is in the blood very fast, and out again very fast. Within 1-2 hours after the event, your body is back to normal.

Facts on Adrenaline

Adrenaline is also known as epinephrine and is produced by the adrenal glands, located on top of the kidneys. Biologic half time is 2 minutes. Its systematic name is (R)-4-(1-Hydroxy-2-(methylamino)ethyl)benzene-1,2-diol

Read More Nerdy Stuff

What happens if we get too much, too long?

Adrenaline kicks can give dizziness, lightheaded-ness and vision changes – and basically it is a strain on the body. Adrenaline is intended to be in the body only short, and is exhausting if prolonged.

This was part 3 of a series of 5

This series takes you through the physics of stress, and how to prevent it.

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