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Adrenaline AKA Epinephrine 101 Guide

People who enjoy frequently practicing extreme high-risk sports have been known to explain that the adrenaline rush they get from their activities keeps them coming back for more. They develop a kind of adrenaline craving. Indeed adrenaline is a powerful hormone that can trigger multiple reactions within our system in a matter of seconds. 

A Brief History of Adrenaline and Epinephrine

The word adrenaline has its origins in Latin, formed by the word ad that means “next to” and the word for kidneys renes, literally meaning “next to kidney”. The adrenaline hormone was discovered by a Japanese chemist named Jokichi Takamine and his assistant Keizo Uenaka in the 1900s. However, until 1904, Fried Stolz and Henry Drysdale were able to synthesize adrenaline in a laboratory and named it epinephrine… called “epi” in medical jargon. (1)

What is Adrenaline?  

Adrenaline or Epinephrine is a hormone and neurotransmitter released from the adrenal medulla at the center of the triangular-shape adrenal glands located on top of each kidney. The adrenal glands produce hormones like cortisol, aldosterone, adrenaline, and noradrenaline. At the same time, they are regulated by the pituitary gland. Also, adrenaline is produced in some neurons, and is part of the central nervous system. 

When adrenaline is released into the blood system due to a physical, emotional, or threatening situation it serves as a chemical mediator transmitting nerve impulses to various organs. By stimulating the sympathetic nervous system, adrenaline activates the fight-or-flight response. 

How Does An Adrenaline Rush Feel?

When the fight-or-flight response is activated, and the adrenaline or epinephrine is released in the body, we can observe signs such as:

  • The capability of lifting heavy objects or running faster. 
  • Rapid heart rate.
  • Excessive sweating. 
  • Shallow breathing. 
  • Dilated pupils which may make things look brighter. Some individuals suffering from anxiety can experience light sensitivity.
  • Dizziness.
  • Shaky hands, arms, and legs. 
  • Excessive nervousness.

What Does Adrenaline Do To The Body?

A sudden and quick surge of adrenaline is called an adrenaline rush. It starts in the brain when we recognize danger within our surroundings. The signal of a possible threat is sent to the amygdala, the part of the brain responsible for emotional processing. 

Later, this signal travels to the hypothalamus that acts as the brain’s control center, and alerts the body of a possible menace using the sympathetic nervous system. When the message sent by the hypothalamus reaches the adrenal medulla, it responds by releasing adrenaline into the bloodstream. Adrenaline travels throughout the body rapidly, causing changes in various parts of the body:

Epinephrine’s Effect on the Lungs 

Adrenaline enables the bronchi and muscles located in the lungs to relax and dilate, increasing the breathing rate. When respiratory capacity is improved, oxygen levels are augmented in the cells. The more oxygen present in the blood allows for better physical performance. 

Adrenaline’s Effect on the Heart and Blood Pressure

Epinephrine or adrenaline works with the heart receptors. As a result, the heart contracts with a higher force, increasing the heart rate and blood pressure. When more blood is pumped by the heart, the muscles intake more oxygen that enables better performance, permitting us to run faster, jump higher or hit harder.

Epinephrine’s Effect on the Eyesight

An adrenaline rush dilates the pupil allowing more light to enter, improving the capacity of seeing and perceiving. This way, we can be aware of everything that happens in our surroundings. 

Adrenaline’s Effect on Energy Reserves

When danger, tension, or alert are present, the body uses an emergency supply of energy stored in the glycogen molecules activated by releasing epinephrine into the bloodstream. These glycogen molecules are derived from glucose. 

Adrenaline’s Effect on Intestinal Function 

When we face dangerous circumstances, the release of adrenaline in the body shuts down the digestion process as this uses a substantial amount of energy that the body may require to face a threatening situation. 

Epinephrine’s Effect on the Metabolism

The discharge of epinephrine triggers a series of metabolic changes in the body, like obstructing the release of insulin into the pancreas, stimulation of glycogen in the liver and muscles. It also raises the blood glucose level and increases lipolysis in adipose tissue to meet energy needs.  

What is the Difference Between Epinephrine and Norepinephrine?

Norepinephrine and Epinephrine are neurotransmitters and hormones with similar chemical structures. However, their main difference is in the effects they have on the body. While epinephrine acts on alpha and beta receptors, norepinephrine works in beta receptors only. Alpha receptors are present in the arteries, and beta receptors are in the lungs, heart, and the arteries of the skeletal muscles. Epinephrine and norepinephrine can:

  • Raise heart rate 
  • Elevate blood sugar levels
  • Increase contractility (the intensity the heart squeezes)

However, norepinephrine boosts vasoconstriction, making the blood vessels narrower, increasing blood pressure. While the epinephrine relaxes the airways, smoothing out and improving breathing. 

Medical Uses Of Epinephrine

The synthetic version of the adrenaline, epinephrine, has made it possible to treat individuals in emergencies.  Like when suffering a cardiac arrest, anaphylactic shock (immunological reaction to food, medication, or insect bites), asthma attacks, bleeding, and more. 

  • In a severe allergic reaction (Anaphylaxis), epinephrine is used because of its immunological properties.
  • In the case of a cardiac arrest, epinephrine is used to increase peripheral resistance by means of vasoconstriction. (2)
  • Epinephrine is present in injectable anesthetics (bupivacaine and lidocaine) as it helps to prolong the anesthetic action due to its vasoconstrictor characteristics.

It is important to note that this type of treatment should be used only in emergency scenarios because of its significant side effects. Furthermore, it should not be employed in patients with glaucoma, cerebral atherosclerosis, or heart failure.

“Excess Adrenaline” Problems 

Research has shown that excess adrenaline levels can cause a series of health problems such as high blood pressure, clogged arteries, and brain changes contributing to developing anxiety, depression, and addiction. The constant release of adrenaline for a long term period can cause:

  • Cardiovascular disease
  • Weight gain 
  • Headaches
  • Lightheadedness, dizziness, and vision changes
  • Metabolic issues
  • Digestive problems 
  • Difficulty concentrating and retaining information. 
  • Sleep disorders

To help control the excess of adrenaline is essential to activate the parasympathetic nervous system, the rest-and-digest response that promotes balance in the body. Activities that stimulate the parasympathetic nervous system are yoga, meditation, deep breathing exercises, tai-chi, together with a healthy balanced diet, and mild to moderate exercise.


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