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  • Writer's picturePatricia Faust

Your Brain on FEAR!

BOO!! Did I scare you? Not likely but I am sure that you have experienced some bone chilling fear at some point in your life. Your brain is uniquely wired to meet fear head-on. In fact, that is a universal trait we all possess. This blog is a summary of an excellent article from How Stuff Works: How Fear Works by Julia Layton. She takes a very complex brain process and explains it in easy terms for us all to understand.

Fear is a chain reaction in the brain that starts with a stressful stimulus and ends with the release of chemicals that cause a racing heart, fast breathing and energized muscles – also known as the fight or flight response. We have more than 100 billion nerve cells that make up the complex communications that are the starting point of what we sense, think and do. These communications function on two different levels of the brain: some lead to conscious thought and others produce autonomic responses. The fear response is almost entirely automatic – we do not consciously trigger the response and, it runs its course before we are even aware of the reaction.

The Fear Response

Neurons are constantly transferring information and triggering responses resulting in dozens of areas of the brain that are at least peripherally involved in fear. Research has found that there are certain parts of the brain that play core roles in the process:

· Thalamus: decides where to send incoming sensory data (eyes, ears, mouth and skin)

· Sensory cortex: interprets sensory data

· Hippocampus: stores and retrieves conscious memories; processes sets of stimuli to establish context

· Amygdala: decodes emotions; determines possible threat; stores fear memories

· Hypothalamus: activates ‘fight or flight’ response.

The process of creating fear starts in the brain and is entirely unconscious. There are two paths involved in the fear response: the low road (quick and messy) and the high road (takes more time and delivers a more precise interpretation of the events). We get the benefit of both paths as they are occurring simultaneously.

The Low Road: take no chances;

· Shoots first and asks questions later (wind or burglar rattling door?)

· Process:

o Door knocking – stimulus

o As soon as you hear sound and sense motion -> sensory data is sent to the thalamus

o At this point thalamus doesn’t know if the signals are signs of danger – or not

o Since it might be danger -> forwards information to the amygdala

o Amygdala receives neural impulses and takes action to protect you

o Amygdala -> hypothalamus – initiate fight-or-flight response

The High Road: considering all the options:

· Process:

o Eyes and ears sense sound and motion -> information sent to thalamus

o Thalamus -> sensory cortex – interpreted for meaning

o Sensory cortex – more than one interpretation of data -> goes to hippocampus

o Hippocampus consolidates information; picks up additional information

o Makes decision based on all information

o Hippocampus sends message to amygdala that there is no danger

o Amygdala sends information to hypothalamus to shut off the fight-or-flight response

The sensory data regarding the door – stimulus – follows both paths at the same time. The high road takes longer than the low road. That is why you have a moment or two of terror before you calm down. No matter which path we are discussing – all roads lead to the hypothalamus. This is the portion of the brain that controls the ancient survival reaction of the fight-or-flight response.

Now a little more detail about the fight-or-flight response: To produce the fight-or-flight response, the hypothalamus activates two systems – the sympathetic nervous system (uses nerve pathways to initiate reactions in the body) and the adrenal-cortical system (uses the bloodstream). The combined effects of these two systems are the fight-or-flight response.

The Sympathetic Nervous System

When the hypothalamus activates the sympathetic nervous system – the body speeds up, tenses up and becomes generally very alert. The sympathetic nervous system sends out impulses to glands and smooth muscles and tells the adrenal medulla to release epinephrine (adrenalin) and norepinephrine (noradrenaline) into the blood stream. These are the stress hormones and cause several changes in the body, including an increase in heart rate and blood pressure.

At the same time, the hypothalamus releases corticotrophin-releasing factor (CRF) into the pituitary gland. The pituitary gland (a major endocrine gland) secretes adrenocorticotropic hormone (ACTH). ACTH moves through the bloodstream and ultimately arrives at the adrenal-cortex, where it activates the release of approximately 30 different hormones that get the body prepared to deal with a threat.

Changes in the Body

The flood of epinephrine, norepinephrine, and dozens of other hormones causes changes in the body that include:

· Heart rate and blood pressure increase

· Pupils dilate to take in as much light as possible

· Veins in skin constrict to send more blood to major muscle groups (responsible for the ‘chill’ sometimes associated with fear – less blood in the skin to keep it warm)

· Blood-glucose level increases

· Muscles tense up, energized by adrenaline and glucose (responsible for goose-bumps – when tiny muscles attached to each hair on surface of skin tense up, the hairs are forced upright, pulling skin with them)

· Smooth muscle relaxes in order to allow more oxygen into the lungs

· Nonessential systems (like digestion and immune system) shut down to allow more energy for emergency functions

· Trouble focusing on small tasks (brain is directed to focus only on big picture in order to determine where threat is coming from)

This blows me away – all of the fight-or-flight process happens before we are even aware of it. This takes my perception of ‘awe of the brain’ to a whole new level. All of these physical responses are intended to help you survive a dangerous situation by preparing you to either run for your life or fight for your life. Fear – and the fight-or- flight response in particular – is an instinct that every animal possesses.

Dial It Down

I subscribed to the DailyOM for the ‘A Year to Clear What is Holding You Back’ course by Stephanie Bennett Vogt.

The following is Lesson 45: Your Indicator to Dial It Down:

What is one thing or issue in your home or life that continues to annoy you, or rattles your cage every time you think about it?

That is your indicator to dial it down. Or back off.

Unleashing a host of stress chemicals is not going to serve you. In fact, it will stop you dead in your tracks.

Today, try noticing when your fight-or-flight kicks in unnecessarily. What can you do to remember to dial it back?


Layton, J. How Fear Works. Retrieved January 31, 2017 from

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