Stress is closely related to the concept of the fight-or-flight response, a cascade of physical responses that occur in all animals during life-threatening encounters. Hormones--specifically adrenaline--flood the bloodstream and prepare the body either to stand and fight or to run away from danger. Throughout the animal kingdom, this response is crucial for survival. For example, the fight-or-flight response allows this zebra to react and run fast enough to escape the jaws of this lioness.
Click on each body system below to see how the fight-or-flight response affects it.
| Body System | Fight-or-Flight Response |
| Heart and Circulation | Heart rate (pulse) increases; blood pressure increases; blood is shunted from the organs of digestion to the muscles of the arms and legs. |
| Brain and Nervous System | Central nervous system activity increases; reaction time is shortened; focus and alertness increase; vigilance increases. |
| Respiratory System | Smaller airways dilate to allow more air to move in and out of the lungs. |
| Vision | Pupils dilate, improving vision. |
The fight-or-flight response allowed our earliest human ancestors to fight back against or escape from large predators. Today, that same "adrenaline rush" can give people the ability to lift immensely heavy objects or to endure unimaginable pain in order to rescue themselves or a loved one from danger. Clearly, stress is not all bad.
Review what you've learned about stress and its immediate effects. Match each physical stress response to the survival benefit it provides.
|
small airway dilation
increased alertness
blood shunted to arms and legs
increased heart rate
pupil dilation
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See a threat more clearly.
Access more oxygen for energy to run or fight.
Oxygen and nutrients circulate faster to provide energy.
Threats are less likely to surprise or outsmart you.
Your muscles have the strength to fight or run.
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Try again.
Question
Is there a difference between stress and the fight-or-flight response? If so, what is it?
