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Understanding the Stress Response and How to Complete the Cycle

Have you been wondering what all this talk is about burnout and the stress response? During 2020 this became a common topic as more and more people suffered from the stress of the pandemic, working from home and the self-isolation of quarantine. Understanding how the stress response works can help you recognize it and learn how to respond to it in more healthy ways.

There are many articles that focus on how to recognize chronic stress and burnout. The goal for this article is to help you understand the process itself and techniques to turn it off.

How Does The Stress Response Work?


The stress response begins in the brain. Once the eyes and/or ears detect danger, like a large barking dog, they send a signal to the amygdala. This input is received by the amygdala, an emotional processing center in the brain, and registers the encounter as a threat. It then sends the processed information to the hypothalamus.


The hypothalamus acts as a command center of the brain. It connects with the rest of the body through the autonomic nervous system (ANS). The ANS controls all of the automatic functions in the body- from breathing to digestion to heart rate and blood vessel dilation.

Sympathetic Nervous System

The autonomic nervous system has 2 parts- the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS). The SNS triggers the ‘fight or flight’ response, increasing heart rate and blood pressure, opening up the lungs and releasing glucose into the bloodstream.

Parasympathetic Nervous System

In contrast, the PNS controls the ‘rest and digest’ system. As a result, it calms the body, directing blood flow to the gut and reducing stress hormones. The PNS takes over to calm the body once the stressor is gone.

Initiating the Stress Response

To activate the stress response, the amygdala sends a signal to the hypothalamus. In response, the hypothalamus activates the autonomic nervous system through the adrenal glands. Once activated, the adrenal glands release a hormone called epinephrine that activates the SNS and triggers the ‘fight or flight’ response.

Maintaining the Stress Response

After the initial surge of epinephrine wears off, the hypothalamus-pituitary-adrenal (HPA) axis kicks in and continues to fuel the stress response by releasing corticotropin-releasing hormone (CRH). CRH then activates the pituitary gland to release adrenocorticotropic hormone (ACTH), which causes the adrenal glands to release cortisol.

What Hormones Are Important In The Stress Response?

Once the stress response is activated, the adrenal glands produce adrenaline (aka epinephrine), noradrenaline (aka norepinephrine) and cortisol.


Adrenaline is a hormone that is produced by the center (medulla) of the adrenal glands and some of the nerves in the central nervous system. Once released, adrenaline acts as a chemical mediator that stimulates the SNS and subsequently, the ‘fight or flight’ response.

Adrenaline is responsible for the following physical effects of stress:

  • Increased heart rate
  • Increased blood pressure
  • Opened airway passages (bronchodilation)
  • Increased size of the pupils


Noradrenaline is closely related to adrenaline, and primarily responsible for the maintenance of cardiovascular tone. Even when the stress response is not activated, noradrenaline is circulating to maintain cardiac and vascular function. To do this, it acts on specialized receptors in heart cells, the nervous system and in the kidneys.


Cortisol is considered the primary stress hormone. It releases blood sugar into the bloodstream, which gives you the energy to fight or flee. In addition, it improves the brain’s utilization of glucose, to help you think quicker on your feet.

The other primary role of cortisol is to limit non-essential functions during the stress response. In other words, cortisol essentially shuts down the immune system, digestive system, reproductive system and growth processes while the stress response is active. 

All of your energy can now be directed towards fighting or fleeing. However, when the stress system is chronically activated your body is unable to heal and repair. Therefore, while your cardiovascular systems is over-activated, the rest of your body is being ignored.

What Triggers The Stress Response?

Acute Stressors

The stress response is intended to respond to an immediate life-threatening event. It evolved to protect us from danger. Once upon a time, this meant running away from a lion and a raging hippo. Most importantly, you were prepared to fight or flee.

Chronic Stressors

In today’s world, the response is still vitally important whether you are a pedestrian about to be hit by a car or a surfer who spots a shark in the water. The response to fight or flee is automatic. You don’t even have time to think about it.

That being said, the response is also activated by many other events that are not life-threatening. This might be a triggering email from your boss, heavy traffic on the way home from work, a frustrating response from your partner, or a public speaking engagement.

Stress Accumulation

Unfortunately, we are exposed to low grade stressors all day. This means that the stress response can be activated over and over and over again throughout just a single day. Literally, from the moment you wake up until the moment you go to bed (assuming you check your email first thing in the morning and watch the nightly news).

How Do You Complete The Stress Response Cycle?

Without properly shutting off the stress cycle, the hypothalamus will keep producing hormones that maintain it. Because the stress response is activated by mildly stressful events that don’t have a clear beginning and end, the stress response can be continuous. 

As I mentioned above, the problem with a chronically activated stress response is that it shuts down the ‘rest and repair’ functions. This means that you are set up for health problems if you do not learn how to turn off the response.

These repeated loops of uncompleted stress cycles build up and can have long term consequences. The Nagoski sisters write about completing the stress cycle to avoid the build of stress leading to burn out. Evidence-based methods of completing the stress cycle include:

  • Physical activity – go for a run or on a bike or hop in the ocean for a quick swim
  • Creativity – pull out some watercolors or crayons and go wild on a blank canvas
  • Laughing – watch a funny movie or spend some time with good friends who make you laugh (laughing activates the PNS)
  • Crying – sometimes you just need to release that pent-up emotional energy with a few good tears. It’s ok to get it all out!
  • Physical affection – a comforting hug or a deep long kiss can help calm your nervous system
  • Deep breathing – breathwork activates the vagal nerve 

Does this cycle of stress apply to you?

I hope this post has given you a better understanding of how the stress response works. When it comes down to it, stress will always be present in your life. Understanding how it works and how to handle it will give you the power to approach stress in a more positive way.

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Kelly Bruno MD Homepage Glacier

Hi! I’m Kelly. I created Recharged Daily to help you reduce stress and burnout by focusing on what’s important to you.




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