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The moment a threat to the heart first strikes the nervous system triggers a “fight or flight” response, every millisecond also triggers the most important component of the brain.
During times of fear, the amygdala – located deep in the medial orbitofrontal cortex – pumps out a series of proteins and chemicals into the brain that help send blood to muscles to amplify the effects of the hormone cortisol.
The number of cortisol spikes an individual experiences will be factored into a style of behaviour, from secrecy and avoidance to aggressive impulses to aggression.
It’s what applies to stalkers, who can affect a person’s relationships and careers for years.
These are some of the effects of fear triggered by triggers such as death threats.
Fear of death
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Fear of death or being harmed is a substantial component of human survival systems.
Its symptoms can vary. According to psychiatrist Dr Pina Hamann, fear triggers may include thoughts of being killed or seriously harmed, or hallucinations in which people hear noises, strange things or touch things, including themselves.
“These beliefs can be triggered by things people have seen or heard, such as being killed in war, or even by a first person shooter video game, a spooky real-life haunt or even a doctor telling someone that they are going to die,” says Dr Hamann.
“Many people imagine that if they had been hit by a car or stabbed that they would feel intense and immediate relief. But in fact the feeling is short lived and the next morning something will trigger it again.”
Body changes and behaviour
Image copyright Getty Images Image caption The amygdala is located deep in the medial orbitofrontal cortex
The amygdala can shift in size, which means that someone with a large amygdala – which is often the case with both obsessive-compulsive disorder and anxiety – will start functioning more flexibly.
This can include skipping their “regular” jobs and taking up work outside their usual field.
In some cases, these changes can lead to physical altercations. Such physiological changes can also have a psychological impact.
As our bodies adapt to cope with the intensity of fear, we experience changes in our social and personal interactions. We can lose touch with family, friends and colleagues, and get upset with a relaxed partner if things start to get out of hand.
Some people even develop issues with post-traumatic stress disorder – which refers to feelings of distress following a serious or life-threatening event – including suicide, where the objective isn’t to kill yourself, but to send a message to people about why someone should kill themselves, for example.
“Previous studies have shown that violent behaviour often goes unnoticed because it doesn’t give rise to obvious signs and a person might not recognise themselves in a typical violent situation,” explains Emily Reynolds, clinical psychology lecturer at Ulster University.
Images: A personal experiment
Image copyright Getty Images Image caption If you fear you will feel sick, dizzy or someone will make you feel physically ill, take some magnesium or glucose
Another “face-changing” side-effect is anxiety. There are two main examples of how our stress hormones impact our daily lives: DHEA and Zinc.
DHEA is the hormone that tells your brain that you feel happy. Zinc, meanwhile, slows your heartbeat and reduces the heart rate.
In situations of intense stress it is not unusual for our bodies to become more sensitive to DHEA, so when you’re pushed over the edge, your body can take the reaction and transfer it into a subsequent bout of worry.
This is a similar effect to having a heart attack.
“Being anxious often leads to blood pressure becoming elevated and this will affect your sense of feeling sick. So if you find you are often suffering from stomach upset or feeling dizzy – either easily or greatly – it’s worth being aware that your body’s often trying to send you a message about what’s going on,” says Dr Hamann.
This story was originally published on Channel 4 News.