Epinephrine and norepinephrine
Epinephrine, commonly known as adrenaline, and norepinephrine, also referred to as noradrenaline, are hormones produced by the adrenal glands that play critical roles in the body's response to stress. Both hormones are classified as catecholamines, released during the fight-or-flight response. Epinephrine increases heart rate, elevates blood pressure, and enhances airflow to the lungs, preparing the body to react to perceived threats. It is also utilized as a medication to treat severe allergic reactions (anaphylaxis), cardiac arrest, and other medical emergencies. Norepinephrine, while functioning as both a hormone and a neurotransmitter, primarily helps regulate blood pressure and maintain alertness, playing a vital role in the central nervous system. Disruptions in the levels of either hormone can lead to various health conditions, including hypertension, depression, and attention deficit hyperactivity disorder (ADHD). Both hormones are essential for maintaining physiological balance but can have serious health implications when their levels are too high or too low. Understanding the functions and effects of epinephrine and norepinephrine can provide insight into their importance in both health and medical treatments.
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Epinephrine and norepinephrine
Epinephrine, also known as adrenaline, is both a hormone produced by the body and a medication. Norepinephrine, also known as noradrenaline, is a chemical in the body that acts as both a hormone and a neurotransmitter, which sends signals between nerve cells. Epinephrine and norepinephrine are nonessential (not required by the body to function) hormones released by the adrenal glands, which are located at the top of the kidneys. Epinephrine and norepinephrine are also known as catecholamines, which means they are released by the adrenal medulla, or inner part of the adrenal gland, as part of the nervous system's fight-or-flight response. During this process, the body uses energy to prepare for a dangerous or stressful situation; the hormones help to replace the energy stores of the muscles so the body can respond to the threat.
Epinephrine
When a person feels scared, nervous, anxious, stressed, or angry, the body releases epinephrine into the bloodstream via the adrenal glands. Epinephrine helps to keep the cardiovascular system healthy. The hormone causes the heart to beat faster and stronger, which increases blood pressure and sends more blood to the brain and heart. It also increases contraction, or the blood flow to the tissues and muscles of the body. It drives up blood sugar and aids in converting stored energy, called glycogen, to glucose in the liver. Epinephrine causes the hairs on the skin to raise by contracting the smooth muscle cells of the skin. In addition, epinephrine relaxes the breathing tubes, which allows a person to breathe more easily.
Several negative health conditions can be caused by too-high or too-low epinephrine levels. High levels in the bloodstream can elevate blood pressure and lead to serious cardiovascular conditions and other medical issues. High levels can also cause adrenal tumors. A condition called Addison's disease is marked by the lack of epinephrine in the bloodstream.
During times of stress, epinephrine and norepinephrine cause the kidneys to stop functioning. The release of epinephrine and norepinephrine constricts the blood vessels, which prevents blood flow to the nephrons of the kidney. This then triggers the renin-angiotensin-aldosterone system, which works to balance the body's fluids and blood pressure, to prevent kidney failure.
Epinephrine is also a medication utilized to treat a variety of conditions. It can be used during cardiac arrest (heart attack), to increase blood pressure during shock (a serious medical condition in which there is not enough blood flowing through the body), and as an inhaler for bronchial asthma. Most commonly, epinephrine is used to treat a severe allergic reaction known as anaphylaxis. Anaphylaxis can be life-threatening, causing the airway to swell or narrow and blood pressure to drop. Severe allergies to foods (nuts, shellfish, etc.), medications, latex, and insect bites or stings (from bees, wasps, etc.) can trigger anaphylaxis. Epinephrine usually is injected into the muscle of the thigh via an auto-injector (known as the brand name EpiPen) to help open the airways and increase blood pressure.
Norepinephrine
Norepinephrine works in two ways: as a naturally occurring hormone and as a neurotransmitter in the central nervous system. As a hormone, it is released by the adrenal medulla with epinephrine when the body is responding to stress. It combines with dopamine and then is released into the bloodstream and affects the brain's response to stressful situations.
It is more commonly produced by the nerves as a neurotransmitter. Norepinephrine is made in the nerve axons, which are the shafts or bodies of the nerves, and is stored in small fluid-filled sacs called vesicles. An impulse is sent down the nerve, which alerts the body to release norepinephrine. Norepinephrine then travels across two nerves and binds to the second one, alerting it to respond.
Norepinephrine has several purposes in the body. As a hormone, it maintains blood pressure; however, norepinephrine can cause blood pressure to rise by making the blood vessels narrow. Like epinephrine, norepinephrine increases the heart rate, releases sugar into the bloodstream, and sends more blood to the muscles of the body. As a neurotransmitter, it helps to speed a person's reaction time and increases alertness and arousal.
Norepinephrine levels that are too high or too low can cause several negative effects on health that affect a person's day-to-day life. Norepinephrine and dopamine help a person to focus. Low levels of norepinephrine can affect a person's ability to pay attention, negatively impacting concentration. This can lead to attention deficit hyperactivity disorder (ADHD). The disorder affects the parts of the brain that help people solve problems, understand others, control impulses, and plan for the future. Several medications (such as Ritalin and Adderall) can be taken to raise and/or maintain levels of norepinephrine and dopamine in the brain. One of these, Strattera, is specifically used to increase levels of norepinephrine.
Low levels of norepinephrine and the neurotransmitter serotonin can affect a person's mood and lead to depression. Depression is a serious condition that can cause feelings of sadness and hopelessness. Several medications (Cymbalta, Effexor, tricyclic antidepressants) can be used to increase norepinephrine and serotonin in the brain to treat or prevent depression.
Hypotension, or low blood pressure, is another side effect of low levels of norepinephrine. Low blood pressure can cause a person to become dizzy and faint. If blood pressure dips very low, the heart and brain can be affected, and the body can go into shock. Several types of shock can be life-threatening. Septic shock is an infection that causes organ failure, while neurogenic shock occurs when nerve signals are disrupted, usually because of an injury to the spinal cord. In these cases, norepinephrine is usually given intravenously to quickly raise the levels.
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