50+ Health Conditions

What Causes Your Fear

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In this Spotlight feature, we will explain the biology of fear: why it has evolved, what happens in our bodies when we are scared, and why it sometimes gets out of control. Scroll down…if you dare.

Everyone can get scared; fear is an unavoidable facet of the human experience.

People generally consider fear as an unpleasant emotion, but some go out of their way to trigger it — such as by jumping out of planes or watching scary movies.

Fear is justifiable; for instance, hearing footsteps inside your house when you know that you are the only one home is a valid reason to be terrified.

Fear can also be inappropriate; for example, we might experience a rush of terror while watching a slasher movie, even though we know the monster is an actor in makeup and that the blood is not real.

Many individuals consider phobias as the most inappropriate manifestation of fear. They can attach themselves to pretty much anything — such as spiders, clowns, paper, or carpets — and significantly impact people’s lives.

Why do we get scared?

As far as evolution is concerned, fear is ancient and, to a certain extent, we can thank fear for our success as a species. Any creature that doesn’t run and hide from bigger animals or dangerous situations is likely to be removed from the gene pool before it’s given the chance to procreate.

Fear’s essential role in survival helps explain why it sometimes seems a little trigger-happy.

In other words, it makes sense to be a little jumpy if you’re an animal in a hostile environment. It’s better to run and hide when your own shadow catches you by surprise than to presume that a shadow is safe, only to be eaten by a bear 5 seconds later.

What happens in the body?

People often refer to the physiological changes that occur when experiencing fear as the fight-or-flight response. Overall, as the name suggests, the changes prepare the animal to either fight or run.

Breathing rate increases, heart rate follows suit, peripheral blood vessels (in the skin, for instance) constrict, central blood vessels around vital organs dilate to flood them with oxygen and nutrients, and muscles are pumped with blood, ready to react.

Muscles — including those at the base of each hair — also become tighter, causing piloerection, which is colloquially called goosebumps. When a human’s hair stands on end, it doesn’t make much of a difference to their appearance, but for more hirsute animals, it makes them seem larger and more formidable.

Metabolically, levels of glucose in the blood spike, providing a ready store of energy if the need for action arises. Similarly, levels of calcium and white blood cells in the bloodstream see an increase.

Triggering the response

The fight-or-flight response begins in the amygdala, which is an almond-shaped bundle of neurons that forms part of the limbic system. It plays an important role in the processing of emotions, including fear.

The amygdala is able to trigger activity in the hypothalamus, which activates the pituitary gland, which is where the nervous system meets the endocrine (hormone) system.

The pituitary gland secretes adrenocorticotropic (ACTH) hormone into the blood.

At this time, the sympathetic nervous system — a division of the nervous system responsible for the fight-or-flight response — gives the adrenal gland a nudge, encouraging it to squirt a dose of epinephrine into the bloodstream.

The body also releases cortisol in response to ACTH, which brings about the rise in blood pressure, blood sugar, and white blood cells. Circulating cortisol turns fatty acids into energy, ready for the muscles to use, should the need arise.

Catecholamine hormones, including epinephrine and norepinephrine, prepare muscles for violent action.

These hormones can also: boost activity in the heart and lungs; reduce activity in the stomach and intestines, which explains the feeling of “butterflies” in the stomach; inhibit the production of tears and salivation, explaining the dry mouth that comes with a fright; dilate the pupils; and produce tunnel vision and reduce hearing.

source: medicalnewstoday.com

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