Defense physiology is a term used to refer to the symphony of body function (

physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...

) changes which occur in response to a stress or threat. When the body executes the "

fight-or-flight The fight-or-flight or the fight-flight-or-freeze response (also called hyperarousal or the acute stress response) is a physiological reaction that occurs in response to a perceived harmful event, attack, or threat to survival. It was first des ...

" reaction or stress response, the nervous system initiates, coordinates and directs specific changes in how the body is functioning (

), preparing the body to deal with the threat. (See also

General adaptation syndrome Stress, either physiological, biological or psychological, is an organism's response to a stressor such as an environmental condition. Stress is the body's method of reacting to a condition such as a threat, challenge or physical and psycholog ...

Definitions

Stress : As it pertains to the term ''defense physiology'', the term ''stress'' refers to a ''perceived threat'' to the continued functioning of the body / life according to its current state. Threat : What constitutes a ''threat'' as it pertains to ''defense physiology''? A ''threat'' may be consciously recognized or not. A physical event (a loud noise or car collision), a chemical or a biological agent which alters (or has the possibility to alter) body function (

) away from optimum or healthy functioning (or away from its current state of functioning) may be perceived as a ''threat'' (also called a

stressor A stressor is a chemical or biological agent, environmental condition, external stimulus or an event seen as causing stress to an organism. Psychologically speaking, a stressor can be events or environments that individuals might consider demandin ...

). Life circumstances, though posing no immediate physical danger, could be

perceived Perception () is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous system ...

as a threat. Anything that could change the continuing of the person’s life as they are currently experiencing it could be perceived as a ''threat''.

Physiological reactions to threat (or perceived threat)

A threat may be either ''empirical'' (an outside observer may agree that the event or circumstance poses a threat) or ''a priori'' (an outside observer would not agree that the event or circumstance poses a threat). What is important to the individual, in terms of the body’s response, is that a threat is

. The

perception Perception () is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous system ...

of a ''threat'' may also trigger an associated ‘feeling of distress’. Physiological reactions triggered by mind cannot differentiate both the physical or mental threat separately, Hence the "fight-or-flight" response of mind for the both reactions will be same.

Duration of threat and its different physiological effects on the nervous system.

Acute Stress Reaction - The body executes the “

Fight-or-flight The fight-or-flight or the fight-flight-or-freeze response (also called hyperarousal or the acute stress response) is a physiological reaction that occurs in response to a perceived harmful event, attack, or threat to survival. It was first des ...

” reaction to get the body out of danger quickly. When the timing between the ''threat'' and the resolution of the ''threat'' are close, the “

" reaction is executed, the ''threat'' is handled, and the body returns to its previous state (taking care of the business of life - digestion, relaxation, tissue repair etc.). The body has evolved to stay in this mode for only a short time. Chronic Stress State - When the timing between the ''threat'' and the resolution of the ''threat'' are more distant (the ''threat'' or the perception of ''threat'' is prolonged or other ''threats'' occur before the body has recovered), the “

" reaction continues and becomes the new ‘standard operating condition’ of the body, chronic Defense Physiology. Continuing in this mode produces significant negative effects ( distress) in many aspects of body functioning (physical, mental and emotional distress).

References

{{Physiology types Physiology Stress (biology) Endocrine system