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Epinephrine is a hormone that helps in regulating many bodily functions. It is usually secreted by some neurons and the medulla of the adrenal glands. It is also known as the adrenaline hormone and is used to regulate visceral functions. It increases the levels of glucose in the blood and increases cardiac output. Epinephrine prepares an individual for the “fight or flight” response. It is a key component of the sympathetic nervous system. It is responsible for controlling the pupil dilation response. A methyl group is present in the nitrogen side chain of epinephrine. This is what differentiates it from norepinephrine. In this article, we will discuss in detail Epinephrine and its functions.
Key Terms: Epinephrine, Adrenaline, Endocrine Glands, Muscles, Oxygen, Medulla, Nervous System, Fight or Flight
What is Epinephrine?
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Epinephrine or adrenaline is a hormone secreted by the medulla in the adrenal glands. The adrenal glands are a part of the ductless endocrine glands. Adrenaline is released in the bloodstream when the body experiences emotions like anger or fear which are very strong. Feeling such emotions causes an increase in heart rate, blood pressure, respiratory rate, pupil dilation, piloerection (goosebumps) and sugar metabolism. This causes the Fight or Flight reaction; it helps in preparing the body for tough situations.
- These hormones give extra energy to the body with the release of excess epinephrine causing the adrenaline rush.
- It helps in preparing the body for arduous activities like skydiving, bungee jumping or jumping out of the way on seeing a car.
- Epinephrine is a neurotransmitter serving as a hormone. They influence different parts of our central nervous system and send blood to body tissues that are under stress.
Functions of Epinephrine
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Epinephrine performs multiple functions in the human body which are as follows:
- In a stressful environment, the hormone is released into the bloodstream to various organs to enable the body to make a selected response.
- It causes air passages and blood vessels to dilate and supply the muscles with oxygen to either fight or flee.
- It triggers the blood vessels to contract to re-direct blood toward major muscle groups, including the guts and lungs.
- The body's ability to feel pain decreases as a result of adrenaline.
- Blood vessels constrict in our alimentary canal to slow digestion.
- Kidneys make more renin (to increase blood pressure).
- Glucose production increases, for energy.
- Breakdown of lipids and proteins takes place.
Positive Effects of Adrenaline on the body
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Adrenaline has some positive effects on our body such as:
- Heart = Adrenaline increases heart rate and contractility. This increases the flow of blood in the body, with blood pressure getting high. Epinephrine injections are specifically given during Cardiac arrest to increase blood flow to arteries.
- Liver = Adrenaline causes glycogen breakdown into glucose. This helps in increasing blood glucose levels as well as free fatty acids. These are used by the body as fuel in situations of fight or flight.
- Muscles = Adrenaline improves muscle reaction to improve breathing. The epinephrine dilates the blood vessels in muscles. It increases oxygen flow to the muscles for better reaction and increased alertness.
- Lungs = Epinephrine or adrenaline causes relaxation of airway muscles. The lungs have smooth muscles which become relaxed with the release of epinephrine. It enables better oxygen flow and intensified respiration. Epinephrine doses in small quantities can help temporarily subside the shortness of breath and wheezing experienced by an asthma patient.
Fight or flight response of the body
Stress Response Cycle & Adrenaline
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The stress response cycle begins in the brain. The brain perceives the danger and sends a signal of distress to the Hypothalamus.
- The Hypothalamus is called the ‘command centre’ as it communicates with the entire body through the nervous system. The signal is forwarded to the sympathetic and parasympathetic nervous systems.
- The sympathetic nervous system further sends a signal to the adrenal glands. These glands release the hormone epinephrine in excess in the body and this triggers the flight or fight action.
- The body is provided with a sudden burst of energy to respond to stressful situations. Whereas, the parasympathetic nervous system helps the calm down after the situation has passed.
- Epinephrine brings several physiological reactions with it. The person going through this might have high blood pressure and rapid breathing.
- Lungs open up, oxygen travels to the brain to increase alertness. Epinephrine also releases glucose from storage sites which gives energy to the body.
These changes are so rapid that many people don’t even realise these.
Stress Response System
Differences between Epinephrine and Norepinephrine
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The differences between epinephrine and norepinephrine are as tabulated below:
| Epinephrine | Norepinephrine |
|---|---|
| Epinephrine affects the heart more. | Norepinephrine affects the blood vessels. |
| It dilates the blood vessels to increase blood flow. | It narrows the blood vessels to increase blood pressure. |
| Epinephrine is produced only in Medulla. | Norepinephrine is produced in the medulla and sympathetic nerves. |
Similarities between Epinephrine and Norepinephrine
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Epinephrine and Norepinephrine are also similar in many ways such as:
- Both are neurotransmitters belonging to the group catecholamines.
- Both of them influence the central nervous system.
- Epinephrine and Norepinephrine both are secreted in response to an emergency.
Things to remember
- Epinephrine or Adrenaline is released by the Medulla of the adrenal glands.
- It’s released in stressful situations and helps the body respond by either taking a flight or fight.
- It belongs to the catecholamines group.
- It increases heart rate, blood pressure, breathing and blood vessel dilation.
- Epinephrine and Non-Epinephrine are similar to each other with just a little difference in structure.
Sample Questions
Ques. What are the functions of the epinephrine hormone? (3 Marks)
Ans. The adrenaline or epinephrine is secreted by the endocrinal adrenal glands. It is also known as the emergency hormone. As soon as the human body experiences a stressful situation, within minutes, this hormone is secreted which increases one’s alertness, reactivity, blood pressure, gives one goosebump, increases breathing rate as well as leads to sweating.
Functions:
- Increases blood sugar levels
- Higher heart contractility and blood flow
- Breakdown of glycogen into glucose
- Increased production of fatty acids
- Breakdown of lipids and proteins
- Relaxes smooth muscles for increased oxygen flow
- Dilates blood vessels for better blood flow
Ques. Explain in detail the importance of epinephrine in the stress response cycle. (5 marks)
Ans. The stress response cycle has many phases and epinephrine is the emergency hormone that plays a very vital role to play in it along with other organs of the body.
- The stress response cycle begins in the brain. The brain perceives the danger and sends a signal of distress to the Hypothalamus.
- The Hypothalamus forwards the signal to the sympathetic and parasympathetic nervous systems.
- The sympathetic nervous system further sends a signal to the adrenal glands.
- The body is provided with a sudden burst of energy to respond to stressful situations. Whereas, the parasympathetic nervous system helps the calm down after the situation has passed.
- Epinephrine brings several physiological reactions with it. The person going through this might have high blood pressure and rapid breathing.
Ques. Explain what is epinephrine and from which gland is it secreted. (2 Marks)
Ans. Epinephrine or adrenaline is a hormone that is released directly into the bloodstream in an emergency. It is primarily responsible for increasing the blood flow output of the heart and raising glucose levels in the blood. Epinephrine is secreted during acute stress, and it prepares an individual for either “fight or flight”
epinephrine is secreted by the medulla of the adrenal gland when it gets a signal from the sympathetic nervous system.
Ques. Draw a diagram of the gland which secretes the epinephrine. (2 Marks)
Ans. Adrenal Gland secretes epinephrine
Ques. List the differences between Epinephrine and Norepinephrine. (3 Marks)
Ans. The difference between epinephrine and norepinephrine are:
- Epinephrine affects the heart more while norepinephrine affects the blood vessels.
- Epinephrine dilates blood vessels while norepinephrine narrows the blood vessels.
- Epinephrine is only placed in the medulla while norepinephrine is produced in sympathetic nerves and medulla.
Ques. List 3 similarities between Epinephrine and Non-Epinephrine. (3 Marks)
Ans. The similarities are:
- Both are neurotransmitters belonging to the group catecholamines.
- Influence the central nervous system.
- Both are secreted in response to an emergency.
Ques. Give examples of some activities that result in epinephrine release and why do you think it happens? (3 Marks)
Ans. Activities like skydiving, bungee jumping, scuba diving or almost experiencing an accident. These are some activities that result in epinephrine release. When the body faces such exciting, adventurous and strong emotions like avoiding an accident, the brain sends a signal to the nervous system which results in the release of adrenaline. This brings a surge of energy to the body also called the adrenaline rush. That’s why when doing any of the above-mentioned activities there is an increase in heart rate, blood pressure and breathing.
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