Lions and Tigers and Snakes, Oh, My

The Reptilian Brain: Our Ancient Guardian

Long before the human brain evolved to be the complex problem-solving organ we possess today, its primary job was to keep our ancestors alive. To do this, the primary function of our ancestors’ brains was to maintain homeostasis (regulating breathing, heart rate, body temperature, blood sugar, etc.) and ensure self-preservation (personal safety, reproduction, and preservation of offspring). The part of the brain involved in controlling these most basic human functions is often referred to as the reptilian or lizard brain. Composed of the brainstem and basal ganglia, these structures are the most primitive component of the human brain found in almost all vertebrate life forms, including fish, amphibians, and reptiles.

The Role of the Reptilian Brain in Survival

In addition to keeping our body’s basic functions operating in unison, the reptilian part of our brain was responsible for activating emergency systems to keep our ancestors safe. This system of organs can increase our heart and respiration rates to supply increased blood and oxygen to our muscles, increase blood glucose to provide needed energy, and stop processes that are unnecessary in the face of immediate danger, such as digestion and ovulation. In other words, this set of structures gets us ready to deal with impending danger which can be either confrontation/fight or avoidance/flight.

The Mammalian Brain: The Commanding Officer

With the above in mind, the interesting part is that this primitive part of our brain, the reptilian brain (basil ganglia and brainstem), does not act independently.  Instead, it needs to be called to action by, if you will, a commanding officer, a part of the brain referred to as the mammalian brain.  The main job of this set of neural structures is to detect danger, assess what is needed to fend off perceived threats, alert the reptilian brain to ready for action (sound the alarm), and set out to mobilize the troops (heart, lungs, liver, muscles, etc.) to either fight or flee.  This part of the brain, doing the perceiving, alerting, and mobilizing, has been coined the mammalian brain because it is found in most all mammals.  Its first presence in humanoids dates back hundreds of thousands of years.  More scientifically, the structures that make up the mammalian brain have been termed the limbic system and is composed of four cerebral structures: the hypothalamus, amygdala, thalamus, and hippocampus. For the purpose of this discussion related to fear, I am going to focus on the amygdala, two almond size structures located close to the center of the brain.

Brain Digram

The Lookout for Danger

So, if we view the mammalian brain, the limbic system, as the “Commanding Officer” of this complex, then the amygdala’s role would best be described as the “lookout.”  Always on the alert, at the sign of the slightest threat, the amygdala will sound an alarm announcing, “all hands on deck”, thereby soliciting the reptilian brain to go into action!  Sounds pretty slick, right?  Well, perhaps not. The problem with this prehistoric system is its orientation to perceive so much of what we encounter, especially novel experiences, as something to be wary of or even as a threat.  As previously mentioned in my Caveman Mind blog, this proclivity was a necessity for the survival of our ancestors. Still, for modern-day humans, this negatively biased, hypervigilant, and often overly reactive system can give rise to unnecessary worry and stress.

The Impact of Modern Life on Our Fear Response

Living in today’s busy and tumultuous world, we are bombarded by endless streams of information from an almost uncountable array of sources, coming at us non-stop, 24/7.  And with all this going on, we are walking around with a brain composed, in part, of a prehistoric system that is constantly on guard for potential threats.  Can anyone say ANXIETY?

woman afraid in major crowd

In my next blog, I will look further into the physiology of the Fight and Flight system so that we might gain a better understanding of why we break out in sweats when we have a close call while driving to work or crossing a street, why we have a racing heart while lying in bed in the middle of the night as our mind ruminates about an upcoming medical test, an upcoming interview or recollects saying something stupid to our boss that previous day.  Why do we get weak in the knees, nausea, and sweaty palms when we are ready to go on stage or get ready to compete in a big game?  In the meantime, remember a lot of what you experience, as fear, stress, and anxiety is a natural part of being human. And while there is no way to avoid our brains’ built-in fearful proclivities, with deliberate practice, committed action, and regular mindfulness practice, we can take back control of how we behave, thereby living a life on purpose.  Living a life informed by our values and ultimately being who and how we want to be as we navigate this adventure we call life.


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