When the instinctual part of brain (limbic system) perceives danger, it sends messages to your Autonomic Nervous System (ANS). The ANS has two parts, being:

• SNS (sympathetic) is activated with effort & stress, gets the body primed for action; and
• PNS (parasympathetic) is activated in states of rest & relaxation

SNS & PNS function inbalance, generally when one is activated, the other is suppressed, and this does not go through the logical part of your brain (neocortex).

The following images provide a few different ways off looking at the system, with more discussion below these.







Fight or Flight

During traumatic events the SNS kicks in and produces a huge adrenalin rush, ie. survival strategy to mobilise body for fight or flight. The reaction:

• Increased breathing & heart rate, more oxygen, blood into big muscles for quick movement,
• No oxygen to stomach (nausea) or brain (lightheadedness), and
• Fast acting system

After the danger or enough time, the feedback loop to the brain says enough adrenalin, PNS then kicks in and relaxation occurs. The chain reaction:

• Halts alarm reaction & adrenalin production, restoring restful state, and
• Is the slow acting system.

Freeze

If fight or flight is not possible, or trauma is prolonged, ANS & PNS can be simultaneously activated, causing a state of freezing/tonic immobility (eg. mouse going dead with cat, rabbit freezing in headlights). The process contains:

• System shuts down and trauma victim enters an altered reality,
• Heart rate slows down, skin goes pale, as if dead,
• Time slows down, no / less intense fear and pain (eg. people falling from heights or mauled by animals), and
• Freezing increases chances of survival & can save life.

An attacker loses interest if the victim appears dead (cat gives up on lifeless mouse, hijacker leaves woman for dead).

Fight, Flight or Freeze?

Fight, flight & freeze are automatic, instinctive survival responses, not thoughtful or considered responses. Which one occurs depends on the limbic system's perception of the strength & time available. For example:

• If time & strength to run away - flee
• If no time but strength - fight
• If no time or strength & death imminent - freeze

What Goes Wrong?

The ANS continues to be chronically aroused even though the threat has passed & is survived. Usual fight / flight response is truncated & the trauma gets "stuck" in the body. Animals don't get PTSD for their instinctual "shiver down the spine" allows trauma to be sequenced through their body (wish we had this ability). Survivors physiological housekeeping systems are messed up by the trauma. Therapy needs to pay attention to the trauma in the body, ie. body therapies, mindfulness and grounding.