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The Stress Response: Everything You Need To Know

More than ever stress has become a part of everyday life. Work-life, financial challenges, health concerns, political and social chaos, and even life at home have become overwhelming to so many. Stress and burnout are everywhere and the impact is devastatingly real. Teachers, doctors, nurses, service workers, managers, and so many others are victims of job-related burnout. At a time when the whole country is stressed out, is there anything that can provide stress relief?

To know how you can beat stress or burnout by building stress resilience, you must first understand the stress response and what is going on inside your body before you can take appropriate action to get some relief.

The Physiologic Stress Response

Autonomic Nervous System Control of the Stress Response

The Physiologic Effects of Stress


The Physiologic Stress Response

Stress is a threat to an organism's homeostasis (or balance). This threat can be real (as in the form of a bear chasing you) or perceived (as in the form of worrying about dying when flying on a plane). A threat (stress) triggers an involuntary physiologic mechanism that involves multiple body systems, organs, neurotransmitters, and hormones. It does so to prepare the body to deal with "danger" to ensure one thing: survival.

Any real or perceived threat will activate the stress response. A stressor is perceived by you through your senses in the brain. If there is danger, even before you become conscious of the threat, your brain sounds the alarm: Danger! Need to survive! Through a series of nerve communications and hormones, your body is prepped to either fight or flee the situation.

The Stress Response

When a threat is perceived by your senses, your body starts to respond through nerve communications and hormones being released into your bloodstream. This neuroendocrine (neuro - nerve, and endocrine - hormone) response is automatic. It happens before your mind becomes conscious of what is going on. This explains why you might unknowingly hit someone when they jump out and scare you. Your brain sensed danger and responded by "fighting".

Ultimately there are 2 main products that are released by your adrenal glands: adrenaline and cortisol. These are released from the adrenal glands and are used throughout the body to turn on all the body systems that are needing to survive and shut down all those not needed to fight or flee. This happens so all the body's resources can be shifted to those things that will help you survive.

If, for example, you need to run away from a bear then your muscles will need as much oxygen and glucose (sugar) for energy as possible. Adrenaline will cause an increase in your heart rate and blood pressure to increase blood flow to your muscles. They also need energy in the form of glucose (sugar) so cortisol will increase your blood sugar levels. At the same time your digestive, reproductive, and immune systems are suppressed because there is no need for those functions when fighting a threat.

Stress Response Physiology

Autonomic Nervous System Control of the Stress Response

The stress response and recovery are controlled by the autonomic nervous system (ANS). Within the ANS, the sympathetic nervous system (SNS) initiates and mediates the stress reaction and response. When a threat is perceived, the SNS signals the adrenal glands to release adrenaline and cortisol in response to a threat.

After you have survived and are safe, your body will need to return to normal. To recover, the parasympathetic nervous system (PSNS) kicks in and balances out all the body systems that have been on high alert. Your body doesn't need immediate access to energy so it will store glucose rather than mobilize it. This is known as the "rest and digest" state. Here your body can focus on other essential functions like digesting your food properly, building your immune system, or reproducing.

In an acutely stressful situation, a healthy SNS will prepare the body to fight or flee. The body cannot remain in this state forever or there can be a number of unhealthy physiologic consequences. To return to balance, a healthy parasympathetic response is necessary.

If there is continued sympathetic activation (continued threats) or if there is an unhealthy parasympathetic response, it becomes difficult to recover and the body can enter a chronically unbalanced state (chronic stress).

The Physiologic Effects of Stress

The effects of adrenaline and cortisol are helpful when you need to run from a bear or fight an attacker. Inside a healthy person, adrenaline and cortisol will:

  • Increase heart rate

  • Increase blood pressure

  • Increase respiratory rate

  • Increase glucose (sugar) production

  • Increase the alert system

  • Increase arousal

  • Suppress insulin production

  • Suppress digestion

  • Suppress reproduction

  • Suppress immune system

  • Lower serotonin (“happy” neurotransmitter)

  • Deplete dopamine (“motivation/pleasure” neurotransmitter)

Problems arise when the body is chronically exposed to these chemicals because the physiologic effects can lead to physical health conditions including:

  • High blood pressure

  • Heart problems

  • Headaches

  • Muscle tension/pain

  • Fatigue

  • Diabetes

  • Skin conditions

  • Upset stomach, constipation, or other digestive problems

  • Sleep problems

  • Asthma

  • Arthritis

  • Sexual dysfunction

  • Depression

  • Anxiety

Knowing that the stress response is your body's danger alert system helps you understand why you physically and mentally feel a certain way when you are experiencing stress. It's not a personal weakness to feel "stressed". It is your body doing what it has evolved to do - protect you from threats. Don't know if you're stressed or not? Ask yourself, "Do I have any physical symptoms of stress?" This is the easiest way to see it in yourself or others around you.

Also, knowing that the stress response is a physiologic response helps you understand what you can do to become more balanced. Rather than rely on the common unhelpful advice to "avoid stress", "eat better", "get better sleep", or "just relax", now you are primed to know that you balance out the stress response with recovery. Your physiology controls the stress response, it also controls your recovery. Knowing how to recover is the key to being less stressed and more balanced.


For information on how to build stress resilience, see the article "Best Practices to Build Stress Resilience" or the Building Stress Resilience page on this site.

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