The Fight or Flight Response

• Fight or Flight Response

  During a stressful event, the endocrine and autonomic nervous systems work together. When a stressor (like a friend startling you) is detected, the hypothalamus activates the sympathetic branch, shifting the body from its resting parasympathetic state to an active, aroused state. This triggers the release of adrenaline from the adrenal medulla into the bloodstream, which increases heart rate and prepares the body for the fight-or-flight response.

  
• In an instant as soon as the threat is detected (an acute response) and is an automatic reaction in the body. Once the threat has passed, the parasympathetic nervous system returns the body to its resting state (the parasympathetic state.) The sympathetic and parasympathetic branches of the ANS are antagonistic to each other; this means that they have opposite effects. The parasympathetic system acts as a brake and reduces the activities of the body that were increased by the actions of the sympathetic branch. This is sometimes referred to as the rest and digest response.