Do you find yourself experiencing frightening physical sensations that come out of the blue?
Do you wake up in the middle of the night with impending thoughts of doom?
In certain situations where an understanding of anxiety is minimal, anxiety can increase to such levels that panic follows.
Anxiety can be considered as a normal response to danger or threat. Immediate or short term anxiety is named the fight/flight response. It is so called due to its effects being aimed towards either fighting or fleeing the present danger. Therefore, the primary purpose for anxiety is to protect the individual.
In our evolutionary history, it was necessary to our survival to have automatic responses when faced with dangers. These fight or flight responses resulted in us having the ability to take immediate action that maintained our safety.
Whilst we are no longer faced with dangers such as those posed by sabre toothed tigers etc, we are occasionally faced with dangers such as those experienced when crossing the road. In such cases if you experienced no anxiety as a car was speeding toward you blasting its horn, the results may be serious.
Fortunately, it is more likely your fight/flight response would take over and you would run out of the way to be safe. This indicates the purpose of anxiety is to protect the organism, not to harm it. As suggested by Barlow and Craske (1988), it would be totally ridiculous for nature to develop a mechanism whose purpose is to protect an organism and yet, in doing so, harm it.
Anxiety manifests itself through the mental system (which includes the actual feelings of nervousness, anxiety and panic and thoughts such as "there is something wrong"); the physical system (which includes all the physical symptoms such as dizziness, sweating, palpitations, chest pain, and breathlessness); the behavioural system (which includes the actual activities such as pacing, foot tapping and avoidance).
In panic attacks the physical system becomes the most important since it is these symptoms which are most easily mistaken as indicating some serious disease.
When danger is anticipated, the brain sends messages to the autonomic nervous system. This has two branches, the sympathetic nervous system and the parasympathetic nervous system. These control the body's energy levels and preparation for action. The sympathetic nervous system is the fight/flight system which releases energy and gets the body ready for action, whilst the parasympathetic nervous system is the restoring system which returns the body to a normal state.
Unfortunately, the sympathetic nervous system tends to be primarily an all or none system. As a result, when it is activated, all of its parts respond, so either all or no symptoms are experienced, which may explain why most panic attack involve many symptoms and not just one or two.
The sympathetic nervous system releases chemicals called adrenalin and noradrenalin from the adrenal glands situated on the kidneys. These chemicals are used as messengers by the sympathetic nervous system and their action often continues for some time.
The sympathetic nervous system activity is stopped in two ways. Adrenalin and noradrenalin are eventually mopped up by other chemicals in the body, and the parasympathetic nervous system (which generally has opposing effects to the sympathetic nervous system) becomes activated and restores a relaxed feeling. Eventually the body will activate the parasympathetic nervous system to restore a relaxed feeling. This means anxiety cannot continue forever, nor spiral to ever increasing and possibly damaging levels. This process of adjustment is called habituation.
An important point is that the adrenalin and noradrenalin take some time to be destroyed. Therefore, even after the danger is over and the sympathetic nervous system has stopped responding, you are likely to continue feeling edgy or apprehensive for some time because the chemicals are still in your system, although this is perfectly natural and harmless.
Source: Craske, M.G., & Barlow, D.H. (1988). A review of the relationship between panic and avoidance. Clinical Psychology Review, 8, 667-685.