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Fight or Fight: The Evolution

Mental Health issues is a big subject ranging from psychology to politics and ethology. MysteriousT presents this article based on research.


The Five Defence States

The main defense mechanisms consist of freeze-alert, flight or fight, freeze-fright, and collapse(Cantor, 2009). Freeze-alert is believed to be evolved from our ancestors naturally as it promoted higher survival chance in their environments (Long & Fanselow, 2012). It occurs as a result of a threat that overpowers our coping abilities and causes vagal withdrawal in one’s body through surrendering to the parasympathetic processes (Cantor, 2009). This causes increased heart rate to 100bpm and is known as the ‘bated breath’ and freezing in one spot. Thus, it believed that the freeze-alert defense mechanism is inherited since it allows for the evaluation of the environment and the threat present (Cantor, 2009). Furthermore, it will permit for the human or animal to consider options of response. This defense mechanism in action was observed in rats where they were placed in a threatening environment and it was noted that they froze and were alerted (Cantor, 2009). Their heart rates were recorded to be in tachycardia which implies that their sympathetic activity has elevated their heart rate due to the persisted defense state (Long & Fanselow, 2012).

With regards to Flight or fight, both are controlled by the sympathetic activity and both are considered to be active defenses that switch with one another if necessary (Cantor, 2009). These two states are differentiated by their association with blood flow to certain areas of the body (Perusini et al., 2015. If the blood flows vigorously to the arms and jaws, then ‘fight’ is in state and if the blood is flowing to the legs then they’re positioned in ‘flight’ state (Cantor, 2009). Thus, they enable particular responses that are appropriate for a threat. It’s believed that flight or fight defense state was enabled in the mammalian eras which disproves the notion that these defensive states were developed in the reptilian era (Cantor, 2009). Research studies have stated there is partial levels of aerobic capabilities of ancient reptiles, therefore not enough energy conserved to be able to fight or run away (Perusini et al., 2015. Hence, it is believed that flight or fight has evolved for the purpose of species to have increased awareness of potential threats, and therefore higher chance of survival (Cantor, 2009).

Likewise, the defence state Freeze-fright also is facilitated for the purpose of responding best to a specific threat (Zanette et al., 2019). Freeze-fight differs from freeze-alert as it is controlled by the dorsal vagal activity of the parasympathetic nervous system and it conveys limitation of other response options considering that the threat is more eminent (Cantor, 2009). This defensive state halts physical movement, even shock or facial reactions, resulting in immobility. Majority of the time and in most documented studies, fear is always present when freeze-fight occurs (Cantor, 2009). The sympathetic nervous system of the body along with the dorsal vagal activation enables an increase in blood flow and therefore stronger heart contractions (Cantor, 2009). This explains why PTSD patients wake up with a pounding heart after flashbacks or nightmares. Similarly, any threatful attack on our ancestors caused the same defence state to occur (Zanette et al., 2019). PTSD patients who suffer from nightmares are proposed to be in a state of freeze-fight and an evolutionary perspective theorises

that nightmares are a symptom evolved for survival purposes (Cantor, 2009). It’s supposed that since the process of storing memories related to survival takes approximately 2 years (hippocampus and cortex replay information for storage processing during sleep), the brain has therefore evolved to ensure the memories are not forgotten by relaying them in the form of nightmares (Cantor, 2009).

The last resort to an attack or to a threatful environment is the defense state of ‘collapse’. Many researchers have given alternative phrases for this defense state, such as submission, faint and death feigning (Cantor, 2009). This defense state is dominated by the parasympathetic nervous system, and it occurs in most organisms (Zanette et al., 2019). For example, a fish who encounters a shark, will go into collapse as its parasympathetic system responds by activating the dorsal vagus nerve, in which enables dorsal vagal shutdown, hence, to collapse. It causes bradycardia and lifeless display of a body (Cantor, 2009).

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