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Fear gets our hearts racing
Racing heart, dry mouth and nausea. They're just some of the things our bodies experience with fear. But why? SCOPE meets physiologist Áine Kelly to find out. She describes fear as "your brain's way of telling you that you are in a dangerous situation and your body is going to have to do something to help you out". To illustrate this, she put Kathriona in a scary situation so we could study her body's reaction. Fight or flight When Kathriona learned she had to abseil down a cliff, she immediately developed a racing heart and dry mouth. Both are signs of the fight or flight response we undergo when faced with danger. Says Áine: "You can either fight the danger in front of you or turn around and run away."
The first thing Áine measured was Kathriona's heart rate. "An increase in heart rate is a classic fight or flight response. You need to make sure your muscles have all the oxygen and nutrients they need, so you need plenty of blood pumping around the body." A normal heart rate is between 40 beats per minute and 100. At 90, Kathriona's was already verging on high. Blood pressure Next, Áine measured Kathriona's blood pressure. Increase in blood pressure is another classic fight or flight response and is necessary to make sure your muscles have enough blood. A normal measurement is 110 or 120 over 70 or 80. Kathriona's was higher than normal at 139 over 71. Saliva production Áine then measured Kathriona's saliva production. In fight or flight mode, your body shuts down any unnecessary systems, including the digestive system. This means your body produces less saliva as it is a digestive fluid. A spit measuring test confirmed that Kathriona's digestive juices were drying up in fear. Other physiological responses to fear include:
The brain We have no control over these responses, so where do they come from? Áine says: "They are coming from your brain. The particular part of your brain that is important is the amygdala." The amygdala is a neural centre involved with the expression of emotions, particularly fear. People with damaged amygdales have trouble feeling fear as well as recognising it in the faces of others. By the time Kathriona reaches the cliff edge, she is sweating, producing very little spit, has a heart rate of 106 beats per minute and a blood pressure of 149/78. Her body is well and truly in fight or flight mode. But in the name of science she fights her fear and away she goes over the cliff edge. Learn more: Check out the BBC's brain map Learn more about fight or flight Read how preparation can help to avoid exam panic |
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