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The physiological and psychological bases of fear

The physiological and psychological bases of fear

April 29, 2024

When in certain situations we are overwhelmed by fear, we experience sensations and reactions that are really alarming and unpleasant at the same time.

This response we offer naturally it is powerful enough to pierce the body and mind of the one who experiences it . The autonomous response of fear arises long before our reason could have decided anything about it, in a kind of chemical summit our organism has already been put into operation, preparing for the flight or for the imminent attack.

Fear is one of the most primitive emotions that exist, was responsible for maximize the chances of survival of our ancestors since it allowed them to respond to threats, but ...


... do we know what mechanisms are put into operation to cause such an avalanche of reactions in our body?

Physiological responses to fear

The sympathetic nervous system It is responsible for the body's maximum performance for a short period of time, just when the individual is in a panic. In the meantime, other functions that are less important in this type of situation decay in a timely manner.

Main physiological effects before the fear that carries out the sympathetic nervous system they are:

  • The muscles contract in an attempt to prepare for the flight, while causing some tremor and general cramps.
  • The number of enzymes in the stomach decreases considerably to ensure energy savings while causing us feeling nauseous.
  • Our heart beats hastily and the blood pressure increases. This causes us to have greater speed in the distribution of oxygen between the muscles. This action can lead to a sensation of tachycardia, tingling in the arms and legs and an annoying buzzing in the ears.
  • Lung breathing is accelerated considerably to increase the exchange between carbon dioxide and oxygen; This action is what causes this annoying feeling of tightness in the chest.
  • Our immune system decays with the intention of preserving energy, which is why we are more exposed to infections.
  • The pupils of the eyes dilate and the tear fluid decreases to increase visual perception.

Once the danger has passed ...

Once this period has elapsed, if we perceive a solution to the situation, the parasympathetic nervous system is reactivated, which will counteract the actions undertaken by your confidant:


  • The eyes will increase your tear fluid , which will cause an inescapable cry
  • The heart will start to beat more slowly and blood pressure will decrease, which can cause dizziness and fainting.
  • Lung breathing will slow down in an attempt to normalize it, which leads to an unpleasant feeling of suffocation.
  • Bowels and bladder empty to promote, if it is the case, a more accelerated flight, which can lead to suffer an uncontrolled urination.
  • Finally, lmuscular tension is lost suddenly , which is why rigidity and laziness arise in the knees.

When the parasympathetic nervous system takes control of our body, it can lead to a situation or state of shock. This set of biochemical responses respond under the name of "Fight or fly", or better known in English as "Fight or flight".


Surely more than one have suffered in our own flesh what is known as panic attack. Well, now we know the physiological functioning through which the organism acts and the functional responses it emits.

Fear-modulating factors

If we decide to introduce ourselves a little more into this construct that we call 'fear', we will see that its scientific study has been extensive.

It has distinguished itself normal fear and the pathological fear based on certain criteria, such as the length of time or the level of interference in daily functioning, among other factors (Miller, Barrett and Hampe, 1974). In order to properly classify it, we must first know the main existing fear factors , that is, its roots and the causes that generate it.

The causes and the initiators of fear

The most consistent factors for classifying the types of media seem to be, according to the classification offered by Gullon, (2000) the following:

  • Social rejection
  • Death and danger
  • Animals
  • The medical treatment
  • Psychiatric stress
  • The fear of the unknown

Types of fear

Assessing these factors we could a classification that discriminates the level of affect of fear in each person and in a particular situation, highlighting the types of fear most studied and treated to date, we find the following distribution:

  • Physical fear
  • Social fear
  • Metaphysical fear

How do we face fear?

First, we must learn to naturalize this emotion , otherwise it can manage to manipulate our lives to the point of becoming a pathological disorder. We must accept the fear of danger and understand its strictest connotations, in this way we will be able to learn to regulate it.

We must think about its main function, since it is a decisive impulse to defend ourselves from a danger, only we have to assess if when this sensation appears we are facing a real danger or an unreal threat elaborated pretentiously by our own mind.

This may seem simple but It is highly difficult to manage on many occasions , since fear tends to paralyze us and there is no point in trying to rationalize it. Fortunately, there are psychological therapies that allow us to influence the psychological mechanisms that install fear in our mind.

"Fear is my most faithful companion, has never cheated me to leave with another"

-Woody Allen

Bibliographic references:

  • Ekman, P. and Davidson, R. J. (1994). The nature of emotions. New York: Oxford University Press.
  • Gullone, E. (1996). Developmental psychopathology and normal fear. Behavior Change, 13, 143-155.

The Chemical Mind - Crash Course Psychology #3 (April 2024).


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