The stress you know may look like this.

A stressed woman is gripping her head

But did you know it can also look like this?

Some signs of stress include sweating, dilated pupils, muscle tension, and no appetite.

Recognizing the signs of stress response in the body can help you manage how you deal with stress.

What Is Stress?

According to the definition of stress in both psychology and biology, stress is a pattern of physiological responses to a threat or stressor.

A man wearing boxing gloves gets into a fighting stance and says

The stress response is our body’s attempt to survive and cope with such threats.

The nervous system is the structure in our body that allows us to feel and deal with threats.

A Crash Course on the Nervous System

The nervous system is the body’s command and communication system.

It consists of the brain, spinal cord, and a network of nerves.

Someone pressing buttons in a command center

During stress response, these two nervous system's structures play a significant role:

Flaticon Icon

Sympathetic Nervous System (SNS)

  • controls the “fight or flight” response

  • stimulates the body when facing a stressful situation

Flaticon Icon

Parasympathetic Nervous System (PNS)

  • controls the “rest and digest” function 

  • relaxes your body after the stress has passed

The changes our body goes through when stressed can be explained using the 3 stages of the General Adaptation Syndrome (GAS).

1. Alarm Reaction Stage

When you encounter a threat, your senses send information to your brain, which triggers a stress response.

A woman warning someone:

The SNS releases the hormone adrenaline into the bloodstream. It prepares the body to either fight or flee from the threat.

This can cause:

Flaticon Icon

  • Increased heart rate to push blood to vital organs

Flaticon Icon

  • Increased oxygen for the brain (alertness) and muscles (strength)

Flaticon Icon

  • Dilated pupils for better vision and awareness

Flaticon Icon

  • Sweat production to regulate body temperature

2. Resistance Stage

After the initial shock of stress, the PNS takes over and the body begins to “rest and digest.

A woman with a face mask is relaxing while taking a massage

The body begins to slowly repair itself by normalizing biological responses. It may take a while for it to fully replenish the resources lost and return back to its pre-stress condition:

  • Energy conservation

  • Lowered heart rate

  • Improved digestion

  • Elimination of waste

However, if the stress persists for longer, the body will continue to stay on alert and move on to the next stage.

3. Exhaustion Stage

Prolonged or chronic stress causes the body to use up all its resources. At this point, it may no longer be able to deal with the threat.

A person gives up and falls to the ground, with the caption: 100% done.

This can look like extreme fatigue, burnout, and decreased stress tolerance.

Under chronic stress, cortisol (aka the “stress hormone”) levels remain high, which can cause:

Flaticon Icon

  • Headaches

Flaticon Icon

  • Increase or decrease in appetite

Flaticon Icon

  • Increased risk of health conditions

Flaticon Icon

  • Muscle pain

Flaticon Icon

  • Digestive problems

Flaticon Icon

  • Trouble sleeping


Prolonged stress brings about negative effects on your physical and mental health. Which of the following techniques can you use to manage stress?

Check Your Knowledge

Flaticon Icon

Jeremy just finished an important presentation at work.

Jeremy spent months working on and stressing over this presentation, so he's glad that he was finally able to finish it.

He has a bit of trouble shifting his focus to other tasks right away, but his pre-presentation jitters have stopped and his palms are no longer sweaty.


What stage is Jeremy likely in?

Take Action

A woman doing yoga. In front of her is a view of the ocean and sunset.

Understand the biology behind stress to better manage it!


Your feedback matters to us.

This Byte helped me better understand the topic.

Get support to take action on this Byte