Understanding Fight or Flight

They exist as a true survival mechanism that is hardwired into our brains, as surely as an electronic fuse will trip when a short occurs.

Fight or Flight: The Physical and Psychological Effects.

It’s been long known that when under extreme stress (including when under attack) the human body will undergo a series of involuntary changes as part of the “fight or flight” mechanisms built into our systems.



Anecdotal evidence from the last five wars (including the current two) plus a number of law enforcement studies, have all confirmed that these effects happen, yet very few delve into why they happen. The largest collection of data was compiled by Dr. Alexis Artwohl and Loren Christensen in their book “Deadly Force Encounters,” and subsequent research papers by Dr. Artwohl, which included interviews with 157 police officers involved in deadly force shootings.

Highlights from the study are shown in the chart, which shows that approximately 80 percent of the officers interviewed experienced the most well-known physiological effects, including tunnel vision and diminished sounds, and that more than 50 percent experienced time distortions or memory loss. Most surprising, more than one in five experienced false memories; that is, they remembered something that never actually happened.

These and other physical and psychological effects have long been attributed to adrenaline or other natural chemicals that flood our bodies during extreme stress, but the “fight or flight” mechanisms that are part of our systems go well beyond a simple chemical dump by our adrenal glands. They exist as a true survival mechanism that is hardwired into our brains, as surely as an electronic fuse will trip when a short occurs.

In this four part series, we’re going to go well beyond explaining what kind of physiological effects you’re likely to experience during a critical incident; we’ll explain why these effects occur and how you can work them into your training regimen. To do that, we’re going to explore the inner workings of the brain and nervous system, as well as offer a visual explanation for each for these amazing effects.

As you read the detail surrounding the remarkable transformations that we’ll undergo during critical incidents, pay particularly close attention to the “Training Tips” that we’ve outlined for each topic. These tips are designed to help you embrace each of the physiological effects into your training plan, so they’ll work to your advantage, rather than your disadvantage.

This is part one of a four-part series, with content and illustrations derived from the book Concealed Carry Fundamentals (www.keyhousepress.com) by Michael Martin.

The “Switchboard” Thalamus

CCW Info: The “Switchboard” Thalamus

The “Switchboard” Thalamus

Our senses (things like sight, sound, and touch) provide sensory and emotional input to our brain, which is routed through a structure called the thalamus. The thalamus used to be thought of as nothing more than a relay station, simply passing signals from the senses to the sensory cortex. Now, scientists think of the thalamus as more of a “switchboard” within the brain, making determinations about where input is routed, and which information is filtered or blocked. As it receives sensory input, the thalamus routes that input to the cortex (the long route) and the amygdala (the short route). Under periods of extreme stress, scientists believe that the thalamus can block any sensory input that it doesn’t consider necessary to the situation.

The “Thinker” Sensory Cortex

CCW Info: The “Thinker” Sensory Cortex

The “Thinker” Sensory Cortex

The cortex not only allows us to plan and reason, it also contains sub-structures to interpret sensory input that has been routed from the thalamus (the “Switchboard). Like the thalamus, the sensory cortex will selectively process or ignore input based upon the task at hand. For example, when we’re focused on a TV program (visual input) we don’t always hear our spouse’s request to take out the garbage; or, when we’re focused on a radio program in the car (audio input), we might ignore the visual input of a stop sign and blow right by it. When we’re under extreme stress, this selective processing and prioritization becomes pronounced.

The “Engineer” Motor Cortex

CCW Info: The “Engineer” Motor Cortex

The “Engineer” Motor Cortex

The motor cortex receives most of its instructions from the thinking and planning part of the brain, but the amygdala (the “Fire Alarm”) also has a direct connection to the motor cortex for those times when it’s necessary for us to do something right now, such as freezing, ducking, raising our hands, or crouching.






The “Fire Alarm” Amygdala

CCW Info: The “Fire Alarm” Amygdala

The “Fire Alarm” Amygdala

Sitting next to the thalamus is a tiny, almond- shaped structure called the amygdala. The amygdala contains most of the brain’s alarm circuits designed to react to any imminent threat passed on by the thalamus. When its alarm circuits are tripped, the amygdala has a direct connection to the motor cortex (that is, it skips the reasoning and planning part of the brain) in order to take immediate action (such as making us duck if something is thrown at our heads), and to the hypothalamus (the “Pharmacy”), to kick our endocrine system into gear. “Evolved” alarms are contained within the amygdala, such as a fear of large, roaring carnivores, while “learned” alarms are accessed by the hippocampus (the “Scrapbook”) such as a fear of snakes with rattles




The “Pharmacy” Hypothalamus, Pituitary gland & Adrenal Gland

CCW Info: The “Pharmacy” Hypothalamus, Pituitary gland & Adrenal Gland

The “Pharmacy” Hypothalamus, Pituitary gland & Adrenal Gland

The sympathetic nervous system involves two additional structures in the brain, namely the hypothalamus and the pituitary gland, as well as the adrenal glands, situated on top of the kidneys. Upon hearing the alarm bells fired by the amygdala, the hypothalamus signals the pituitary gland to release ACTH and endorphins into the bloodstream. ACTH alerts the adrenal glands to release adrenaline (also known as epinephrine), and endorphins act as a natural painkiller by blocking the body’s pain receptors.

The “Scrapbook” Hippocampus

CCW Info: The “Scrapbook” Hippocampus

The “Scrapbook” Hippocampus

The hippocampus provides access to our memories and personal experiences, including any “learned” threats. That recall will include more than just a visual snapshot of the learned threat; it will also recall information about the context and situation surrounding the object. For example, if an individual had been attacked by a thug wielding a baseball bat, the sight of another individual carrying a baseball bat might fire the alarm circuits if the rest of the context met other stored criteria, such as an aggressive facial expression on the part of the person with the bat. On the other hand, a baseball bat in the hands of a smiling little leaguer most likely would not fire those circuits.

The Brain and Central Nervous System

The brain is made up of a variety of interconnected structures, but the ones we’ll concentrate on are those involved in sensory input and sensory processing, reasoning and planning, movement, and the brain’s “alarm circuits.” We’ll also take a look at a key component of the nervous system called the sympathetic nervous system. To make it a bit easier to understand, we’re going to use everyday descriptive terms (such as the “Switchboard”) in addition to using the technical term (such as the “thalamus”).

Training Tip No. 1

Practice your stance using the body position that the short route will force you to take anyway. Square your body to the target, and take up a short crouch. When drawing from the holster, begin with your hands up near your face in the startle position, rather than at your sides. Include point / intuitive / index shooting as part of your training regimen, in addition to sight shooting. In other words, you’ll need to be prepared for your motor cortex forcing your eyes to lock onto a six-foot tall attacker, rather than a 3-millimeter wide front sight.

CCW Info: The manual dexterity that we’ll lose under the effects of adrenaline just happens to be the same dexterity required to manipulate holster retention devices, safeties, and slide releases.

The manual dexterity that we’ll lose under the effects of adrenaline just happens to be the same dexterity required to manipulate holster retention devices, safeties, and slide releases.


Training Tip No. 2

Learn to manipulate your firearm’s controls as though you were missing your fingertips. That means ignoring your slide release, and racking (or releasing) the slide by grasping it between the palm and four fingers of your support hand. If you want a taste of what your hands might actually feel like under the affects of adrenaline and extreme stress, try this: Run through a malfunction drill (using dummy rounds mixed with live rounds), after soaking your hands in a sink full of water and ice cubes for a minute or two. The resulting hand shake and lack of feeling will give you a small taste of the real thing.

The Brain’s Long Route and Short Route

Of the components discussed, the amygdala (the “Fire Alarm”) is responsible for initiating the body’s “fight or flight” defenses whenever it receives sensory input that matches predefined alarm circuits. Sensory input reaches the amygdala from the thalamus (the “Switchboard”) along two paths. One path is a direct connection, while the second path is first routed through the sensory cortex (the “Thinker”). The route through the cortex is known as the long route, and the direct connection is known as the short route. The components along the long route are often referred to as the higher brain, while the components along the short route are often referred to as the lower brain or reptilian brain. Although input is passed from the thalamus along both paths, in most cases, the lower brain remains passive, and our movement and other activity is driven by our higher brain as it processes and “thinks about” the input that it’s receiving.


Side effects will include a loss of manual dexterity in our extremities (most importantly, our hands) and our hands may shake from the loss of blood and the influx of adrenaline.


In cases where the information flowing along the paths matches a predefined alarm circuit, the amygdala effectively throws a switch, and within microseconds, it executes a series of tasks that may include signaling the motor cortex (the “Engineer”) to duck into a crouch, rotate toward the perceived threat and lock our eyes on that threat; and it might send a message to the hypothalamus (the “Pharmacy”) to get adrenaline and endorphins moving into the system. Much faster than it would take to think through the situation, the short path through our brain has already prepared us for fight or flight, and it might have already saved us from serious injury or death if it froze our motor cortex before we stepped in front of a speeding bus, or ducked our head to protect us from a flying rock.


The Effects of Adrenaline & Endorphins

As mentioned in the introduction to the structures of the brain and nervous system, the sympathetic nervous system is responsible for releasing adrenaline and endorphins into the system. Adrenaline immediately prepares the body for “fight or flight” by increasing blood, oxygen, and glucose to the major muscles including the heart. It increases heart rate and oxygen consumption by the lungs, and it dilates the pupils.

Side effects will include a loss of manual dexterity in our extremities (most importantly, our hands) and our hands may shake from the loss of blood and the influx of adrenaline. In addition, the lack of blood on the surface of our skin and the effect of endorphins released by the pituitary gland will provide us with an elevated pain threshold. This can allow us to fight long after we might have given up from injuries, but it also means that we’ll need to check ourselves and loved ones for injuries in the immediate aftermath.


Adrenaline immediately prepares the body for “fight or flight.”


Next month’s topic: In part two, we’ll explore how the physical structure of the eye and the filtering ability of the brain combine to cause tunnel vision and heightened visual clarity. We’ll also look at the causes of auditory exclusion, and how we can work that expectation into our training regimen.



[ Michael Martin is a firearms instructor and author, living in Woodbury Minnesota with his wife Sara and two little boys, Jack and Sam. Michael is the author of “Concealed Carry Fundamentals” and “Minnesota Permit to Carry a Firearm Fundamentals,” www.keyhousepress.com. Michael is also the owner and director of Minnesota Tactics (www.mntactics.com), a firearms training organization specializing in introducing beginners to the world of self-defense, firearms, and the shooting sports. Michael is also a certified NRA instructor, and a member of the International Association of Law Enforcement Firearms Instructors (IALEFI). ]



Fight or Flight: Summary of Physical and Psychological Effects.

Fight or Flight: Summary of Physical and Psychological Effects.







FIGHT OR FLIGHT: Summary of Physical and Psychological Effects



Effects of the Brain’s “Alarm Circuits”

  • Reflexive Crouch
  • Hands Elevated to Protect the Face
  • Head Turned and Eyes Locked on Threat


Effects of Brain’s Signals Being Prioritized or Filtered

  • Tunnel Vision
  • Heightened Visual Clarity
  • Diminished Sounds
  • Slow Motion Time
  • Memory Loss
  • Memory Distortion or False Memories
  • Inability to Count


Effects of Adrenaline and Endorphins

  • Increase in Strength
  • Heightened Pain Threshold
  • Decrease in Fine Motor Skills

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