A near miss while driving, a thud on the front door after dark or waking at 2 am to the sound of a telephone are external factors capable of inducing fear or anxiety. Our pulse quickens and our muscles tense, even after the crisis is averted.
For a long time, emotions were considered to be unique to human beings, and were studied mainly from a philosophical perspective. (1) Fear and anxiety are evolutionary benefits which help us determine a threat, and plan for the future.
Anxiety and fear are adaptive behaviors. Sensory nerves perceive a danger and send a signal to the hypothalamus in the brain. The hypothalamus alerts the pituitary gland — which releases a chemical into the bloodstream — and simultaneously transmits a nerve signal down the spinal cord.(2)
The chemicals released by the pituitary gland combined with the nerve signals activate the adrenal glands, secreting adrenaline and energizing the body to react.(2) This is called the fight or flight response.
When a person experiences an unrelenting, repeated fight or flight response out of proportion to, or in the absence of, an external threat, he or she may have an anxiety disorder.