Are you a Tiger, Gazelle or Opossum?: Part one, the nervous system’s response to stressors.

​Lindsay M. Adler, LMFT, CEDS, E-RYT 200 

Have you ever watched a nature show where you see a tiger being approached by a predator? How does that tiger respond? How about a gazelle grazing on grass when a tiger comes along? How does that gazelle respond? Lastly, have you even seen a dog corner an opossum in a backyard? What does the opossum do? 

The tiger will attack, the gazelle will flee and the opossum will play dead. Although each of these responses is different, the animals use each technique for survival.

As humans, we may not be faced with the threat of being eaten, but we experience our own types of stressors and threats. These stressors can include arguing with a loved one, approaching work deadlines, sitting in rush-hour traffic or experiencing a traumatic event. 
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Even though we have evolved to be different from the tiger, gazelle and opossum, we still have similar responses to threatening experiences. 
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Today, let’s take a look at how our brain functions under stress, and in a later blog, I will share with you how to work with your nervous system to function in a healthy way under stress. 

Exploring the brain from the bottom up

Our brain has three parts and each part has a specific role in helping us deal with stressors. Here they are listed from the bottom up, meaning the most primitive to the most advanced.

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1. Reptilian Brain (AKA the brain stem and cerebellum). This part of our brain is the most primitive, hence the word reptilian. Its role is to control our basic life-sustaining functions such as maintaining and regulating our heart rate, breathing, balance and body temperature.
2. Mammalian Brain (AKA the limbic system). This part of our brain first emerged with mammals. The main components of limbic system are the hypothalamus, amygdala and the hippocampus. The limbic system is shaped partly by genetics such as temperament and partly by our early childhood experiences. It is the part of the brain responsible for our emotions and helps us judge if is something is pleasurable or scary.
3. Rational/Cognitive Brain (AKA the neocortex or prefrontal lobe). This part of our brain makes us uniquely human. It is more developed in humans and is the center of language and abstract thought. The rational brain helps us to understand concepts, accomplish goals and manage time. ​

When each of these parts are in balance, we are likely feeling good physically and mentally. However, when there is a stressor, perceived stressor or threat, our brain begins to kick into overdrive, leaving some parts of our brain more active than others. 
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The parts of our brain that are the most active when stressed are the reptilian and mammalian parts, which we often call our emotional brain. Our emotional brain becomes more or less active, depending on the intensity of the current stressor and our past experiences with stressors or trauma. (For example, someone who has experienced a past trauma might experience a current stressor with more intensity than someone who has not experienced a trauma. Therefore, the person who had a trauma might have a more active emotional brain in the face of the stressor.) 

It is important to understand how our brain and body function under stress, so we can work with our body to decrease the negative effects of stress. For instance, besides mental health concerns, chronic stress is also linked to pain, heart disease, high blood pressure, hormone imbalances and digestive problems.

Under pressure

When we experience a stressor, such as work-related issues, a car accident or an argument with a friend, our brain begins to sense a danger through the use of our senses. This information is gathered in the thalamus and then sent to our limbic system, which uses our perceptions and past experiences to interpret what could be happening. The amygdala (the center of our emotional reactions in our limbic system) helps our brain detect if what we are experiencing is related to survival, such as fighting back an attacker. It does this with the help of the hippocampus, which links the sensory information to old experiences. Then, if the situation is interpreted as threatening, the amygdala adds intense emotions associated with the stressful or threatening situation in order for us to take action. It is important to note that our limbic system has been wired to often interpret uncertain situations as threatening. This is because we have been wired to protect ourselves as much as possible. 

The engagement of our limbic system is unconscious and the information moves very fast. This is why when we are experiencing an emotionally heightened experience, such as an argument, we respond without thinking. For instance, in an argument, we don’t typically think, “I am going to yell now to get my point across.” Instead, we suddenly begin raising our voices without noticing.

The rational brain also plays a role in our reaction to stress. However, it often is left in the back seat. This is because information is sent to the pre-fontal cortex at a slower rate. Using the example above, “I am going to yell now to get my point across” would be a rational brain response to a stressor because it is using higher levels of functioning such as reason.  Since the limbic system is so much faster than the rational brain, we typically don’t make this decision consciously but only realize much later that we have raised our voices.

Fight or Flight 
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Once the information from the threat is processed through the limbic system and our brain says, “YES, DANGER!”, our brain tells our body to start to react. This reaction comes from our hypothalamus and brain stem, releasing stress hormones such as cortisol and adrenaline. This activation tells our autonomic nervous system to activate. Our autonomic nervous system controls bodily functions such as our heart rate, breathing and blood pressure. So, our heart rate starts to increase, we begin to sweat and breathe rapidly. Our body is ready for action. 

So, do we respond like the tiger and fight back? For instance, do you argue back, raise your voice or anger easily?

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Or do we run away like the gazelle? Meaning, in face of stress do you isolate, avoid or walk away?

Each of these responses is part of our animal instinct; a way to protect ourselves from something, which seems threatening. Although adaptive, these responses can become harmful when we are reacting to something as if it is a threat when in fact it is not.
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If we respond in flight or flight mode because of heightened emotions or because our brain has been wired to be more hypervigilant of stressors due to trauma, then it can have negative impacts on our mental, physical and social wellbeing. ​

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Freeze/Collapse

Now, you might be wondering, well what about the opossum? 
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Just as our body responds through the autonomic nervous system when we face a stressor, our body can also use another part of our nervous system, the parasympathetic nervous system to deal with a stressor.

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The parasympathetic nervous system is the rest and digest system. It works in opposition of the autonomic nervous system, meaning if the autonomic nervous system is activated, then the parasympathetic nervous system will not be activated. This makes sense because if you were running from a attacker, you wouldn’t want to be calm and relaxed, otherwise you wouldn’t take action to save yourself from being hurt. We need our autonomic nervous system to help us survive. But we also need our parasympathetic nervous system to return us back to a state of balance. 

Since we live in a world of constant stressors, most people have overly activated autonomic nervous systems and under activated parasympathetic nervous systems. So, often I am encouraging people to work on activating their parasympathetic nervous system more. However, there are a few cases where the over activation of the parasympathetic nervous system leads to a state of freeze, AKA playing opossum. 
This often occurs for those who have experienced a trauma in which they felt trapped or if they have had multiple traumas. Instead of moving into a state of fight or flight to protect themselves, they move into a state of freeze or collapse. 

Freeze is a function of the reptilian portion of our brain. In the event of a threat that feels unavoidable, the individual’s body shifts to a state of shutdown. Their body systems slow down and they lose any activation of the pre-frontal cortex in order to survive. This allows them to save energy and stall reactions in the brain so they cannot experience physical or emotional pain. 

Let’s look at two examples. 

1. The opossum is cornered by a dog in a fenced yard. Knowing it can’t defend itself or run away, it becomes frightened and instead of taking action, it goes into shock. An automated response occurs and the opossum goes into a comatose state appearing dead. The dog doesn’t want to eat a dead animal, so plays with it, and then runs away. The opossum gets up, shakes it off and runs away to safety. 
2. A woman is in a car accident. She is pinned in her car and can’t get out. There are flames around her and she begins to feel as if she might die. All of a sudden, she becomes numb in her body and mind. A firefighter comes to save her from the car. When she is out of danger, the firefighter asks her if she is “okay”, but she can’t seem to respond. She feels disconnected and can’t remember what happened. 

The freeze or collapse response also has its purpose, by helping us cope with an unavoidable threat. However, it too can be harmful. Examples include, when we experience numbing but it would be healthier to take action and feeling disconnected when there is no danger. For example, say your brain was wired to respond in freeze, because of a past traumatic event in which you couldn’t move, and you get into a disagreement with your significant other. However, instead of being able to shift into rationally discussing the topic, you find yourself completely numb. You can’t find the right words and you don’t feel any emotions. Your partner then wonders if you even care about them because you seem so disengaged. 

Understanding our nervous system

Now that you have the knowledge about the different responses: fight, flight and freeze, I encourage you to take notice and think about how your body reacts to stressors. Often times, we will respond differently depending on the situation. This also makes sense because if we feel we can fight, we will and if we feel we can flee, we will. And if neither option is available to us, we freeze.

Most importantly, knowing how you typically respond to stressors will help you learn how to respond more healthfully in the future. Sometimes this takes working with a therapist. For now, take notice and in an upcoming blog, I will share some tools to help you shift your reactions.

Resource: van der Kolk, Bessel. (2014). The body keeps the score: brain, mind, and body in the healing of trauma. New York: Viking.