Fight or Flight – Peter Walker

The Defensive Cascade (Focus, Freeze, Flight, Fight and Flop)

The defensive cascade, commonly referred to as the “fight or flight response”, is a coordinated set of behaviours, supported by physiological changes, that promotes survival in the face of some form of threat. As threat escalates, the nature of the defense response changes in a predictable way and this is supported by our physiology. This will be described below. The response is normal and adaptive; in fact, we would be at great risk without it. The defensive cascade is prominent when experiencing distress, such as when we’re anxious or angry.

Consider the following, somewhat far-fetched, scenario. On the drive in to the appointment you have with your psychologist you hear on the radio that a dangerous black bear has been sighted roaming the streets close to the practice. At this point you would most likely to move into the “focus” stage of the defensive cascade. Your body will start becoming physiologically aroused. Your heart rate would increase (tachycardia), blood pressure would rise (hypertension), your pupils would dilate and your senses would scan the environment for threat, in this case, bear related threat. This increased attention, concentration and focus on threat increases our survival as we are better able to avoid the threat.

Let’s say you make it to your appointment without incident, however the bear is in the same geographical location and decides to climb the stairs of the psychology practice in which you’re situated, out of curiosity. It is likely that the close proximity you are maintaining in relation to the bear would lead you to enter the next phase of the defensive cascade, freezing. To support this behaviour, physiological arousal (heart rate increases, blood pressure elevation, increased respiration etc) would continue to increase and additionally the body would increase in tension and maintain a rigid posture. This response increases our chances of survival as it reduces the chance that the bear will detect us.

If, despite maintaining a freezing posture, the bear continues its advance toward you, attempts would be made to run or flee. This is the flight phase of the response. It is important that your body is prioritising functions that assist your escape. Energy will be diverted away from lower priority functions such as digestion (hence the dry mouth, nausea, occasional vomiting and voiding of bowels) and directed to our muscles to maximize our speed. We may also demonstrate a fear potentiated startle response, ie a more pronounced tendency to startle due to arousal, which allows us to leap into action and as they say “hit the ground running”.

Perhaps we are cornered and unable to successfully escape from the bear. With the escalating threat, we may enter the fight component of the defensive cascade. Here, attempts are made to confront the threat physically. An interesting physiological development is particularly useful here. The brain modulates our experience of pain in a variety of ways such that our pain

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sensitivity reduces. Most of us have experienced this phenomena when playing sport. In the excitement of the game we notice little physical pain and only after the game has finished and we have calmed down do we notice the cuts and scratches we have sustained. A reduction in the intensity of pain helps to lessen the distraction that would be associated with injury and in turn increases the chance we survive.

When escape appears impossible and an individual’s demise seems certain, the final stage of the defensive cascade can occur. This stage can be referred to as “flop” and consists of fainting (threat induced syncope) and quiescence. It is important to note that this is a very rare and only occurs in situation where death is imminent and appears unavoidable. A commonly cited example is described in the 19th Century Scottish explorer David Livingstone’s diaries, when he was attacked by a lion in Mabotsa in present day South Africa.

“I saw the lion in the act of springing upon me. He caught me by the shoulder and we both came to the ground together. Growling horribly he shook me as a terrier dog does a rat. The shock produced a stupor similar to that which seems to be felt by a mouse after the first gripe of the cat. It caused a sort of dreaminess in which there was no sense of pain nor feeling of terror though I was quite conscious of all that was happening. It was like what patients partially under the influence of chloroform describe: they see the operation but do not feel the knife. This placidity is probably produced in all animals killed by the carnivora and if so is a merciful provision of Creator for lessening the pain of death.
David Livingstone (1857). Missionary Travels (pp. 11-12). London: EW Cole.
Post threat recovery- Once we consider we have become safe our body rapidly enters a recovery state. This state is characterised by exhaustion, a strong desire to withdraw, remain still and often sleep. Our sensitivity to pain returns and this ensures that any wounds are protected and attended to, aiding the healing process. Cardiovascular function (heart rate and blood pressure) and respiration normalise. It has been suggested that this behavioural response is what accounts for the extreme exhaustion that occurs after people have been in a stressful or threatening state for a period. They appear to “run on adrenalin” and then experience profound fatigue. Interestingly, modern models of psychological therapy for post traumatic reactions encourage those who suffer trauma to “go with” this behaviour. They are encouraged to “lay low”, surround themselves with the support they need, sleep as much as they require and create surroundings that feel safe. It is only later that exposure based treatments are suggested, and then only if the individual is displaying signs that their adjustment has been compromised.
These are the normal, hardwired behaviours that humans have evolved to manage threat. They are not pathological themselves, but can become so when our experience of them is interrupted in various ways. Read the blog post about panic disorder for an example of when the response becomes a problem.


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