Have you ever wondered what goes on in the brain when safety is threatened? It’s important for people (kids and adults alike) to have a basic understanding of brain anatomy and function. I typically explain it to children using Dan Siegel’s hand model of the brain.

It’s pretty simple, so long as you can make a fist. Tuck your thumb into the palm of your hand, and then close your fingers over that.

Your wrist now represents the brainstem, or what’s often referred to as the lizard brain. This is the oldest part of the brain, and we share this structure with other animals. The brainstem is responsible for basic drives for survival.

Now, your thumb tucked inside the structure represents the limbic system, which is pretty much the emotional powerhouse, among serving other functions. When strong emotions arise, the amygdala (part of the limbic system) sets off an alarm in the mind, and everything switches to high alert to assess for threats and promote survival.

Finally, the front of your knuckles and fingers represent the prefrontal cortex (PFC). The PFC is located in our heads behind our forehead. This is the part that most sets us apart as humans from other animals.

The PFC is where all executive functioning transpires – decision making, judgment, learning, etc. These functions take a backseat when the limbic system goes on high alert, which means that judgment can be skewed (what once seemed dangerous may now look like a good idea, or others around us who were once trusted as safe now appear as a threat); we may not make the most informed decisions that are in our best interest; and learning new information or skills is near improbable. 

Fear. One primary function of the middle prefrontal cortex is the conscious modulation of fear through gamma amino-butyric acid (GABA), a primary inhibitory neurotransmitter. When a fear-inducing stimulus registers in the brain, it does so in one of two ways.

The first route is known as the ‘low road,’ which means that it enters the thalamus and is directly routed to the amygdala, causing the individual to respond before meaning is assigned.

In the second pathway, known as the ‘high road,’ the fear eliciting stimulus also enters the thalamus but is sent to the sensory cortex before being sent on to the amygdala, providing the individual an opportunity to relate the current stimuli to past experiences and assess the threat level.

Research suggests that traumatized individuals tend to process information that evokes unprocessed implicit memories (such as physiological arousal, smells, objects) in a manner that mimics the fear response, even in the absence of danger. I will share more about how trauma affects memory in a future post. 

Body. When exposed to a threat, the body prepares itself to respond in three ways: flee, fight or freeze. When the mind perceives that escape is achievable, blood flow is redirected to the arms and legs, mobilizing the physical body to evade danger.

However, when those same neurobiological mechanisms determine that escape is unavoidable, physiological responses transpire to prepare the body to fight:

• heart rate and respiration increase
• blood flow is redirected to large musculoskeletal systems to fend off the attack,
• and blood flow is pulled away from other organs, especially in the stomach and intestines, resulting in gastrointestinal distress, or a ‘gut feeling.’

Yet when the mind perceives that neither fight nor flight is possible, the body freezes and enters a state of ‘tonic immobility.’ The purpose of tonic immobility is believed to promote survival by ‘faking death,’ as well as to lessen the experience of pain and provide the mind with an altered sense of reality.

When this happens, the intense energy created from readying the body to stay and fight, compounded with equally intense energy to flee, overloads the nervous system. The body must be able to discharge this energy in order for proper nervous system regulation; otherwise, the energy then manifests in the body as psychosomatic symptoms:

• headaches
• digestive issues
• fatigue
• aches and pains, among others

While the body is designed to discharge this energy and recover from a traumatic experience, we know that immediate recovery does not always take place for a variety of factors. From here, post traumatic stress disorder can result. Read more about PTSD here.