The nervous system is composed of the brain, spinal cord, and nerves that go throughout the body. The nervous system is the command center of the body, responsible for our thoughts, movements, and automatic processes such as breathing and digestion. Importantly, the nervous system is also responsible for our experience of emotion. Understanding your nervous system can help you become more aware of your emotions and how you can manage them without becoming overwhelmed.

Let’s start with a brief overview of the brain using this handy model created by Dr. Dan Siegel and based on the triune brain model by Paul McLean. It can be helpful to familiarize yourself with three major parts of the brain: (1) the brainstem (responsible for basic survival functions like breathing and heart rate); (2) the limbic system (the emotional center of the brain, responsible for our fight/flight/freeze response) and (3) the cortex (the “thinking and reasoning” part of our brain, responsible for managing big emotions, connecting with others, and helping us make thoughtful decisions).

hand model of the brain, triune brain — (Image from Kerra-Lee Wescombe, 2021)

When all three parts of the brain are working together, we feel safe and connected to others. This is the optimal zone of nervous system arousal, known as our window of tolerance, or our social engagement system.

Window of Tolerance

Window of Tolerance, a term coined by Dr. Siegel, refers to the zone of nervous system arousal in which we are able to function and engage with other people most effectively. In this zone, our brain can process stimuli without becoming overwhelmed. This means the thinking part of our brain, the cortex, is online and helping us keep our nervous system (and emotions) regulated. This state is associated with our parasympathetic nervous system and is also known as the “rest and digest” state.

When we are within our window of tolerance and difficulties arise in our day, we are able to handle them without our nervous system becoming dysregulated. This means that we can manage our emotions without getting overwhelmed.

Within this zone, we feel safe and socially connected. We are grounded, open, curious, flexible, and able to take on challenges. We feel calm but not exhausted, energized but not anxious. When emotions like frustration or sadness take us closer to the edge of our window, our thinking brain is able to use strategies to keep our nervous system regulated so we can stay within our window. This diagram shows how our nervous system ebbs and flows when we are within our window and our brain is able to regulate our emotions:

Sometimes, however, we can get thrown out of our window of tolerance when our limbic system sends our thinking brain offline. This happens when it senses danger and sends our nervous system into an automatic fight, flight, freeze, or collapse response. This state is associated with our sympathetic nervous system.

Fight/Flight/Freeze/Collapse

Our limbic system contains the part of our brain responsible for sensing threat and protecting us from danger. It can make split-second decisions to keep us safe, whereas our thinking brain wouldn’t be able to respond as efficiently to danger. Therefore, when our limbic system senses danger, it can turn our thinking brain offline and trigger our fight/flight/freeze/collapse response, moving us outside our window of tolerance in its attempt to keep us safe.

When we are in this state, our nervous system is over-activated, or hyperaroused. Our body is alert and ready to fight or flee danger—or it may freeze to avoid danger. Our breathing and heart rate quicken, our hearing becomes sharper, our skin sweats, our muscles tense, and our pupils dilate. Here we can feel anxious, panicked, angry, or out of control.

In the collapse response, on the other hand, our nervous system is under-activated, or hypoaroused. Our heart rate drops, our breathing slows (we may even hold our breath), and we feel immobilized. It can be easy to confuse the freeze and collapse responses, so it may be helpful to imagine you are playing a high stakes game of hide and seek. The seeker is right outside your hiding place. You are tense, alert, hyperaroused because you know they might find you: this is freeze. Suddenly, they lock eyes with you, and you’re defeated, hopelessness: this is collapse. In collapse, we can experience exhaustion, numbness, dissociation, depression, shame, and hopelessness.

window of tolerance, somatic therapy seattle — (Image from Mind My Peelings, 2019)

The fight/flight/freeze response evolved over ages to keep you safe and alive. It was very useful in our early hunting and gathering days when we encountered regular threats to our survival, like dangerous wild animals. And it is still useful when you are faced with real threats to your safety, like when you have to slam on your brakes to avoid hitting the car in front of you. In this case, you want to be dysregulated so you can respond effectively: You don't want to be in your window all the time.

However, our fight/flight/ freeze response is also frequently triggered by non-life-threatening occurrences, like a first date, a bad grade, a deadline, an argument, or a visit from your in-laws. While these are stressful events that can result in ebbs and flows in your nervous system and move you toward the edges of your window, sometimes our nervous system responds as if these events are life-threatening, sending us outside our window into fight/flight/freeze.

fight or flight response, trauma therapy seattle

Why do I react so strongly to stress? Your window of tolerance can narrow and widen based on a number of factors, even throughout the day. If you have experienced trauma or you are going through a stressful time, your window can become very narrow. When your window is narrow, your nervous system is even more attuned to potential dangers, triggering your fight/flight/freeze response more often and for even smaller “threats.” This means your limbic system may sense danger when there is none. Unfortunately, by trying so hard to protect you, your limbic system is unintentionally sending your nervous system on a roller coaster ride that can keep you from experiencing safety and connection.

Expanding your window

How can you expand your window of tolerance? An important step in expanding your window is getting to know your nervous system a little better (you’re already doing this!) and starting to notice what it feels like both when you are within your window and when you are outside your window. You can start to notice what your body feels like when you are calm and connected—and what your body feels like when your emotions are dysregulated. You can start to take note of the types of triggers and situations that your limbic system labels as dangerous.

An equally important step is taking care of your body’s most basic needs like sleep, healthy food, and exercise. Even factors like feeling tired or hungry can narrow your window. Do you tend to snap at others more easily when you’re hungry for dinner? That’s because when your body is running low on something it needs for survival, your window can shrink. Anything that puts your body on high alert-–like physical or emotional pain, perfectionism, self-criticism, and disconnection-–can be a force that narrows your window.

Learning strategies for managing stress and finding ways to connect with other people are also ways to expand your window. Additionally, mindfulness and self-compassion are practices that can make your window bigger over time. Working with a mental health professional to process trauma and difficulties can also help you expand your window and get back to feeling safe and connected.

Coming back into your window

How can you come back into your window once you’ve gone outside? When your limbic system has sent your thinking brain offline and you are outside of your window of tolerance, there are many things you can do. As a general rule of thumb, if you are in fight/flight/freeze mode (hyperarousal), you may need to release energy and then sooth. If you are in collapse mode (hypoarousal), you may need to add energy to your system.

To release energy and then decrease arousal from fight/flight/freeze: First, you might try releasing the energy. Dance, go for a walk, run up and down the stairs, shake your body all around. Then, find something soothing. This might include: deep belly breathing (with exhales longer than inhales), laying on the ground, using a weighted blanket, drinking tea, listening to soothing music, making comforting food, stretching your body, giving yourself a hug, meditating, practicing yoga, or engaging in the 5-4-3-2-1 grounding exercise (find 5 things you see, 4 things you can touch, 3 things you can hear, 2 things you can smell, and 1 thing you can taste).

To increase arousal from collapse: Try out some physical activity like dancing, walking, or even just simply sitting up straight or standing and feeling your feet on the ground. You can also try listening to energizing music, rubbing your arms and legs, or stomping your feet on the ground.

Additional ways to regulate include taking a cold shower or dunking your face in ice water, journaling, doing something creative like drawing or playing an instrument, and increasing your emotional vocabulary (get out that emotion wheel and put a name to what you are feeling!).

Co-Regulation: All of the above tools are focused on what we call self-regulation (tools that you can use on your own). However, co-regulation (tools that are used with others) can be just as important for coming back into your window (as well as widening it). This might look like asking for a hug, petting your dog or your cat, or calling a friend. The people in our lives we feel safe with are one of our greatest resources when it comes to reducing stress, so reaching out for support is a great way to come back into your window of tolerance.