What is a Panic Attack?

Here is the actual definition of a "Panic Attack" as written in Wikipedia:

• Panic attacks are very sudden, discrete periods of intense anxiety, mounting physiological arousal, fear, stomach problems and discomfort that are associated with a variety of somatic and cognitive symptoms.
  
  The onset of these episodes is typically abrupt, and may have no obvious triggers. Although these episodes may appear random, they are a subset of an evolutionary response commonly referred to as fight or flight that occur out of context. This response floods the body with hormones, particularly epinephrine(adrenaline), that aid it in defending against harm.
  
  Experiencing a panic attack is said to be one of the most intensely frightening, upsetting and uncomfortable experiences of a person's life.
  
  According to the American Psychological Association the symptoms of a panic attack commonly last approximately thirty minutes. However, panic attacks can be as short as 15 seconds, while sometimes panic attacks may form a cyclic series of episodes, lasting for an extended period, sometimes hours. Often those afflicted will experience significant anticipatory anxiety and limited symptom attacks in between attacks, in situations where attacks have previously occurred.
  
  

  Panic attacks are commonly linked to agoraphobia and the fear of not being able to escape a bad situation. Many who experience panic attacks feel trapped and unable to free themselves.

  The effects of a panic attack vary from person to person. Some, notably first-time sufferers, may call for emergency services. Many who experience a panic attack, mostly for the first time, fear they are having a heart attack or a nervous breakdown.