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The Role of Adrenaline in Fight or Flight Response

Updated on September 21, 2013
Chemical Structure of Adrenaline (Epinephrine). This is a hormone that plays an important role in fight or flight response
Chemical Structure of Adrenaline (Epinephrine). This is a hormone that plays an important role in fight or flight response

Adrenaline Junkie

The term ‘Adrenaline junkie’ is used to describe an individual who enjoys dangerous activities in order to get an adrenaline rush. For adrenaline junkies who are involved in extreme sports, ‘normal sports’ just doesn’t do it anymore. Adrenaline junkies tend to push their limits with the craziest, scariest, fastest activities such as hangliding, freeskiing, freediving, BASE jumping, cliff jumping, body boarding, canoeing, Extreme motorsport, ice climbing, free running and bungee jumping. Other Adrenaline junkies would go for shoplifting or even fighting to get high on adrenaline.

Fight or Flight Response

Have you even found yourself in the life-threatening situation? Say you were wondering in the forest and find yourself face-to-face with a mountain lion. Your nervous system and your endocrine system will communicate with each other to prepare your body for action.

The moment you have seen the threat and realize that you might die, information is sent to the brain. In response, an electrical signal will be sent from the brain down to the Adrenal glands (little glands located at the upper part of the kidney) by a portion of the brain called the Hypothalamus. The Adrenal gland is going to secrete Adrenaline (also known as Epinephrine) into the blood stream. In blood adrenaline level is now at a pick.

Adrenaline will then flow to the rest of the body and has different effects depending on where it goes. Adrenaline is going to cause vasodilation in the muscles to increase blood flow in the muscles. The increased levels of Adrenaline triggered by the fight or flight mechanism and its effects on different parts of the body is also referred to as ‘Adrenaline rush’.

Effects of Adrenaline (Epinephrine)

In the Eye

In the eye, Adrenaline will bind to adrenoceptors resulting in the contraction of the radial muscle of the iris there by making the pupils to dilate. That is, the pupils become enlarged. This will allow more light into the eye and result in brighter and sharper images. This is important because in the presence of a threat, you would want a clear view of your surrounding.

In the Liver

Adrenaline will bind to surface receptors of the liver to trigger a pathway inside liver cells. An enzyme called glycogen phosphorylase is released in the liver cells. This enzyme breaks down glycogen stored in the liver into individual glucose molecules. This process will lead to a rise in the blood sugar level and is known as Glycogenolysis. Glucose molecules will be transported to muscle cells to provide a boost of energy. This is important because glucose can be quickly broken down to produce Adenosine triphosphate (ATP).

In the Lungs

Adrenaline will bind to receptors on smooth muscle cells of bronchioles and causes the muscles there to dilate. This will relax these muscles hence allowing more oxygen to diffuse into the blood. Adrenaline will also cause dilation the arterioles and will speed up breathing rate in lungs. The purpose of increasing the rate of inspiration and expiration is for the body to absorb more oxygen into the blood stream and expel more carbon dioxide.

In the heart

Adrenaline will stimulate cells of the heart to beat faster. This will speed up the heart rate. This is important because oxygen, glucose, hormones and other chemicals can now circulate much faster throughout the body to cells that need them.

In the Skin

Adrenaline will bind to receptors on the smooth muscle cells in the skin and this will cause the muscle to contract. The hair on the surface of the skin will then be raised. Adrenaline also binds to receptor that causes the contraction of sweat glands resulting to beads of sweat.

In the Digestive System

Adrenaline is going to cause vasoconstriction to blood supply of the digestive system. This is because during a ‘fight or flight response’, digesting the burger you ate a couple of hours ago is not really a priority. This will shutdown in order to send more blood to other locations such as your muscles.

Adrenaline is an efficient messenger and an important player in the fight or flight response. It signals many different types of cells throughout the body and causes many different types of effects that will allow the body to response to the threat. You would now have to either stand and fight (the mountain lion) or flee.


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    • thebiologyofleah profile image

      thebiologyofleah 4 years ago from Massachusetts

      Great summary of Adrenaline actions in Fight or Flight- thanks for sharing. Wonder if there is anything to adrenaline junkies having attentuated effects of Adrenaline overtime and so they seek out bigger and scarier things in order to continue to feel the same rush?

      Interesting stuff-thanks for sharing!

    • profile image

      Scarlett 15 months ago

      Thanks greatly you really aid us

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