Adrenaline is a hormone produced by the adrenal glands during high-stress or exciting situations. This powerful hormone is part of the human body’s acute stress response system, also called the “fight or flight” response.
It works by stimulating the heart rate, constricting the blood vessels, and dilating the airways, all of which work to increase blood flow to the muscles and oxygen to the lungs.
Also, it is used as a medical treatment for some life-threatening conditions, including anaphylactic shock. In the US, the medical community largely refers to this hormone as epinephrine, although the two terms can be used interchangeably.
Dangerous activities, like skydiving, can cause an adrenaline rush.
The adrenal glands are located directly above the kidneys in the human body and are approximately 3 inches (7.62 cm) long. Adrenaline is one of several hormones produced by these glands. Along with norepinephrine and dopamine, it is a catecholamine, which is a group of hormones released in response to stress.
These three hormones react with various body tissues, preparing the body to react physically to the situation that causes stress.
Fight or Flight Response
The term “fight or flight” is often used to characterize the body’s reaction to very stressful situations. It is an evolutionary adaptation that allows the body to react quickly to danger.
Dilated airways, for example, allow the body to deliver more oxygen to the lungs quickly, increasing physical performance for short periods of time.
Blood vessels constrict throughout most of the body, redirecting blood to the heart, lungs, and major muscle groups to help drive the reaction.
Adrenaline significantly increases the heart rate.
When a person is faced with a potentially dangerous situation, the hypothalamus in the brain signals the adrenal glands to release adrenaline and other hormones directly into the bloodstream.
The body’s systems react to these hormones in seconds, giving the person an almost instantaneous physical boost. Both strength and speed increase, while the body’s ability to feel pain decreases. This hormonal surge is often called an “adrenaline rush.”
High levels of adrenaline can cause insomnia.
Adrenaline Side Effects
In addition to a noticeable increase in strength and performance, this hormone often causes increased awareness and increased breathing. The person may also feel lightheaded, dizzy, and experience vision changes. These effects can last up to an hour, depending on the situation.
Too much adrenaline over time can cause the hippocampus to shrink, affecting memory.
When there is stress but no real danger, a person can feel restless and irritable. This is in part because adrenaline causes the body to release glucose, which increases blood sugar and gives the body energy that has no outlet.
Many people find it beneficial to “blow off” adrenaline after a particularly stressful situation. In the past, people handled this naturally through fighting or other physical exertion, but in the modern world, high-stress situations that involve little physical activity often arise.
Exercise can use up this extra energy.
Although adrenaline can play a key role in the body’s survival, it can also cause detrimental effects over time. Prolonged and elevated levels of the hormone can put enormous pressure on the heart muscle and, in some cases, cause heart failure.
Also, it can cause the hippocampus to shrink. High levels of adrenaline in the blood can cause insomnia and nervous nerves, and are often an indicator of chronic stress.
First synthesized in 1904, adrenaline is a common treatment for anaphylaxis, also known as anaphylactic shock. It can be given quickly to people showing signs of severe allergic reactions, and some people with known severe allergies carry epinephrine auto-injectors in an emergency.
For these people, the dose must be assigned by a licensed medical professional in advance and instructions must be given on how and where it should be administered.
Adrenaline is also one of the main medications used to treat low cardiac output (the amount of blood that the heart pumps) and cardiac arrest. It can stimulate the muscle and increase the person’s heart rate.
Also, by concentrating blood in vital organs, including the heart, lungs, and brain, it helps increase the chances of a more complete recovery.
Adrenaline can spark a flight response fight.