Monday, November 26, 2012

All Magic Comes at a Cost.

Like most things in this life, anything worth having comes at a cost.  This rings true in the context of the fight or flight response.  This subconscious survival response has played it's part in keeping us and our ancestors safe through time but there have been some costs to our health, both physically and mentally.  We will take a look at both in this post.

As we have already seen, some of the feats the human body and perform when this response kicks in are quite breath taking, and often times unbelievable.  The increased speed, strength, endurance and pain resistance that the epinephrine induces comes with a pretty big side effect.  Like any high performance machine, the body can only work at this turbo boosted level for a limited period of time.  Once the immediate danger has passed or the large amounts of glucose released into the system are used up, you are left feeling an extreme level of exhaustion.  You're likely to feel light headed and barely able to move or exert any force.  This is the dreaded "adrenaline dump".
The effects of an "adrenaline dump" are quite temporary, with bodily service resuming once normal levels have been restored.  A sports drink containing simple sugars can help to replenish the vast amounts of glucose used up and increase recovery

Perhaps the most damaging effect that this survival response can have on the body is its role in the anxiety disorder PTSD (Post Traumatic Stress Disorder).  PTSD is a disorder that can effect people that have gone through times of extreme stress and trauma such as war and natural disasters.  PTSD is caused when the sufferer mentally re-lives the experience causing their fight or flight response or parts of it, to be constantly switched on. The effects of this can be crippling, not only mentally but physically.  Nightmares and phobias of places that trigger memory of the trauma are common, there is also the possibility for the loss of emotion too.  Physically, hyperarousal often manifests and leads into loss of sleep as well as the possibility of hypervigillance.  Prolonged activation of the response can also lead to complications with the sufferers immune system.
 Although this condition has been around a long time, relatively little is known of it and we are still searching for a better understanding.  At the current time, the best responses to patient recovery have come through group and individual psychotherapy.  There are also a few pharmaceuticals on the market that can help ease some of the symptoms.

Mind Control

So far we have been focused on the physiological mechanisms and effects of an adrenaline surge, this post is going to take a look at how the brain deciphers the signals and activates the fight or flight response.

The entire fight or flight process is a complex one that takes place in our subconsciousness.  For ease of explaining the process I will break it down into steps.
  1. Sensory information is taken in by the eyes, ears and body, and directed towards the brains Thalamus.
  2. Sitting atop of the nerve stem in the middle of our brain, the Thalamus is the brains nerve center.  From here the sensory information is split and routed in two directions.
  3. One destination is the frontal cortex, located in the neocortex.  This area of our brains is what separates us from the chimps, it is where all our higher mental functions take place.
  4. The second destination is the Amygdala, located just in front of the Thalamus, this is the brains threat evaluation center.  As the sensory information flows into here it is evaluated for any signs of danger. 
  5. Before a response can be initiated the Amygdala will project the information of the perceived threat to the neocortex.  It is here that our higher mental capacity analyses the threat in greater detail and decides if there is threat or not.  If the coast is clear it will tell the Amygdala to "stand down" and not initiate the reaction.

As well as threat perception the Amygdala is also where our brains learn emotional association.  For example, being stung by a bee as a infant.  Whilst consciously we may not remember the incident, the Amygdala will store the information that involved so that as an adult, the sound of a bee buzzing past your ear will illicit a fearful response.
With this system being kept in check by the neocortex it is understood that situational training can condition the mind to react to stress and fearful situations.  A key skill for a soldier in combat where the difference between fight or flight can mean safety or mortal danger.

  •   LR Mujica-Parodi, HH Strey, B Frederick, R Savoy, D Cox, Y Botanov, D Tolkunov, D Rubin, J Weber: Chemosensory cues to conspecific emotional stress activate amygdala in humans. PLoS One 2009, 4:e6415. 
  • LeDoux, J. E. The Emotional Brain: the Mysterious
    Underpinning of Emotional Life (Simon & Schuster, New
    York, 1996).

Tuesday, October 23, 2012

Real Life Avengers

We've all grown up watching superhero cartoons/movies and have all been obsessed by Marvel Avengers (well, maybe just me then).  Many of you will have asked the question amongst your friends "If you could have a super-power what would it be"?  Most people respond with the classics "Flight" or "Invisibility".  While they may be out of our reach (for the moment) there is one power that, to a degree, we all have within us.  Super-strength.  Admittedly it is a far cry from the gamma fueled rage ball that is the Incredible Hulk, but compared to the usual parameters that the human body functions within it can allow us to perform some quite extraordinary feats.

Let's look at the case of  Lydia Angyiou of Ivujivik in Quebec, Canada.  41 year old Lydia was with her children outside of a local youth center after their local hockey game.  Everything was fine until Lydia spotted a wild Polar Bear eying the children up.  It is at this point her trusted fight or flight response kicked in.  Now, most of our subconscious' would realize that hand to hand combat with a 1000lb wild bear is bad business and use all that extra energy and muscle capacity to run as fast our legs could carry us.  In Lydia's case her motherly instincts over-rode the flight aspect and ran at the bear to utilize the "fight" aspect.  What ensued was nothing short of miraculous.  Fighting the beast bare-handed, Lydia managed to harass and occupy the bear long enough for one of her neighbors to run home and retrieve their gun to shoot the bear.  After four shots the bear was finally downed.  Despite being bloodied, Lydia was otherwise fine.  

 So, how does a 41 year old Canadian mother with no training whatsoever, go toe-to-toe with a 1000lb wild beast and live to tell the tale.  First off it must be noted that there was an immense degree of luck involved.  One swipe with those huge claws connecting on a vital artery and its curtains for Lydia.  Outside of the luck needed there was still a physiological response within Lydia that allowed her to fight without being completely overwhelmed. 
Let's map it out.  First, the sight of the bear threatening her boys stimulates Lydia's hypothalamus.  Form here a chemical signal is sent directly to the adrenal glands and activating the sympathetic system, which kicks her body into an excited state.  The release of epinephrine and norepinephrine raise Lydia's heart rate, respiration and a huge release of glycogen into the blood stream, ready to fuel her action.  The increased blood flow and glucose provides the muscles with a super charge of energy, allowing Lydia's muscles to function at a capacity way beyond her usual means.

In the next post we will look at the aftermath of these superhuman exploits on the body.

  • George, Jane. "Polar bear no match for fearsome mother in Ivujivik." Nunatsiaq News. February 17, 2006.
  •  Marsden, C.D. and Meadows, J.C. "The effect of adrenaline on the contractions of human muscle." The Journal of Physiology. 1970. &blobtype=pdf

Thursday, September 27, 2012


We've all experienced it in one way or another.  The kid being bullied in the playground, his heart racing and his hands shaking, time seemingly slowing down for him as he throws a wild hay-maker at the bullies; or being chased by the vicious dog from next door, you feel as if you could have given Usain Bolt a run for his money.  How about the stories of people ripping off car doors at the hinge to save a loved one from a car wreck?  These scenarios are all linked by a survival response passed down to us by some of our earliest ancestors.  This response is most commonly known as the "Fight or Flight" response.



The  "Fight or Flight" response is the human bodies emergency reaction to grave danger.  Once the body is threatened, a chain reaction occurs designed to prime it ready for fighting/fleeing the immediate danger.  Once a imminent threat as been identified, the sympathetic nervous system sends a signal down to the adrenal glands situated at the top of the kidneys.  This causes the glands to release adrenaline (also known as epinephrine), norepinephrine and cortisol into the blood stream.  From here several systems are pressed into action.  Glucose is released into the blood stream from the kidney ready to supply energy, The heart rate speeds up, increasing blood pressure to insure that all necessary functions have an ample supply.  Pupils dilate and tunnel vision occurs, there is a momentary loss of hearing (think about the last time you experienced this, can you remember any sounds?).  In effect, all power is routed to the bodily functions that give you the best chance of confronting or escaping the potential danger, with those not needed being reduced dramatically or switched off.  This involuntary priming of your physiological survival functions happens in an estimated 1/100th of a second!

This subconscious survival reaction has played a large part in the survival and evolution of our species. From helping our ancestors to escape the predators of their time, through to giving them the ability to fight for and defend their food.  In more modern times this response can be used to explain some of the more incredulous stories of human feats of strength when faced with tragedy.  

In later posts we shall look a closer at this phenomenon and discuss some of the good and bad effects of this most primal of responses.  

  • Cannon, Walter B (1936). Bodily Changes in Pain, Hunger, Fear and Rage.
  • Henry Gleitman, Alan J. Fridlund and Daniel Reisberg (2004). Psychology (6 ed.). W. W. Norton & Company.