Quote:
Originally posted by Bill Harsey
before all that.
|
Before anyone gets into listing the sympathetic nervous system responses... there is a key reaction much more important for some of you HIGHLY trained guys...
The prime ‘directive’ of the human brain is to promote survival and procreation. Therefore, the brain is ‘over-determined’ to sense, process, store, perceive and mobilize in response to threatening information from the external environment. All areas of the brain and body are recruited and orchestrated for optimal survival tasks during the threat. This total neurobiological participation in the threat response is important in understanding how a traumatic experience can impact and alter functioning in such a pervasive fashion.
In order for any experience to be dealt with, traumatic or not, it must be ‘sensed’ -- it must be experienced by the individual. The first step in experiencing is sensation. The first ‘stop’ of this sensory input from the outside environment (e.g., light, sound,etc) is the lower, more ‘regulatory’ parts of the brain(brainstem and midbrain).
As the sensory input comes into the brain stem and midbrain,
it is matched against a previously stored patterns of activation and if unknown, or if associated with previous threat, an initial alarm response begins. The alarm response begins a wave of neuronal activation in key brainstem and midbrain nuclei which contain neurons utilizing a variety of neurotransmitters (e.g., norepinephrine, dopamine, serotonin), neuromodulators and neuropeptides such as ACTH, corticotrophin releasing factor, vasopressin.
A cascade of activity is initiated in these primitive areas of the brain which moves up to more complex parts of the brain.
In addition to sending these signals to higher parts of the brain, this cascade of activity also initiates a set of brainstem and midbrain ‘responses’ to the new information from the environment, allowing the individual to react in a near-reflexive fashion. In many instances, the brain’s response to incoming sensory information will take place well before the signals can get to the higher, cortical parts of the brain where they are ‘interpreted’.
At the level of the brain stem and midbrain, there is very little subjective perception.
It is only after communication with cortical areas that the individual is able to make more complex, cognitive associations which allow interpretation of that internal state of anxiety or fear.
Simply stated, then, the fear response will involve a tremendous mobilization and activation of systems distributed throughout the brain. Because the system alter itself in a ‘use-dependent’ way in response to patterned, repetitive neuronal activation(training), a state of repetitive trauma's will result in a set of ‘memories.
This overview describes the sensing, storing and perceiving elements of the response to threat. At each level of the brain, as the incoming input is ‘interpreted’ and matched against previous similar patterns of activation, a response is initiated. The brain responds to the potential threat. This immediate response capability is very important for rapid response to potentially-threatening sensory signals – the classic example of this is the immediate motor action of withdrawal of the finger after being burned – or the jump that takes place following an unexpected loud sound (startle response). Clearly,
in order for the brain to react in this immediate, ‘un-interpreted’ fashion, the more primitive portions of the brain (i.e., the brainstem and the midbrain) must ‘store’ previous patterns of sensory input which are associated with the threat – there must be ‘state’ memories – memories of previous patterns of sensory input which were connected with the experience .
The classic ‘response’ to the threatening cues involves activation of the autonomic nervous system. This ‘fight or flight’ reaction involves the physiological manifestations of alarm, arousal and the emotion of anxiety (e.g., profuse sweating, tachycardia, rapid respiration). These physical symptoms are manifestations of activation of the autonomic nervous system and the hypothalamic-pituitary axis, again, an adaptive response to the impending threat.
