Norepinephrine and epinephrine--also known as noradrenalin and adrenaline--are chemical hormones located in the adrenal glands. Norepinephrine and epinephrine are chemicals that dictate metabolic responses within the body, such as oxygen release in muscles, blood vessel dilation and constriction and raising blood pressure. These processes are activated when the body needs to respond to emergency situations and then recover from them. The two chemical processes compliment each other and have only slight differences.
Epinephrine contains two amino acids known as tyrosine and phenylalanine that join to make one compound. Two-carbon chains and this newly combined amino acid compound help the body to make blood-binding proteins that encourage epinephrine's circulation through the bloodstream.
Norepinephrine, produced by the enzyme dopamine hydroxylase, is similar to epinephrine in that it contains two combined amino acids and two-carbon chains. Norepinephrine however, includes hydroxyl, a form of additional hydrocarbon that binds to a nitrogen atom. Interestingly, specific cells in the adrenal gland can change norepinephrine to epinephrine as needed for different biological functions, according to the Textbook of Physiology, 8th Edition.
During emergencies, when the body needs to be alert, responsive, and self-preserving, epinephrine sends chemical hormonal messages throughout the body to allow for greater muscle strength, stronger lung functions, greater blood volume, and enhanced senses. This newly formed ability allows for greater strength, timing and endurance. After the emergency passes, the body needs to be restored to its original functioning level to remain healthy. Norepinephrine and epinephrine work to return the muscles to a resting state, calm breathing, decrease the senses and allow other bodily functions, such as hunger, thirst and elimination, to reactivate. Without these safety valves, the human body could not protect itself and would burn out like an abused transmission in an automobile. These processes in the body are sometimes referred to as the "Fight or Flight Syndrome."
Effects of Norepinephrine
Norepinephrine works like epinephrine in that it also increases blood pressure and stimulates respiration and gastrointestinal contractions, but the two chemicals balance each other. Norepinephrine decreases heart rate and increases the actions of the peripheral nervous system by constricting blood vessels. It also constricts blood vessels in the muscles and skin, and decreases stimulation of the bronchial airways in the lungs to return the body to a state of homeostasis or of basic daily functioning. Every minute the body readjusts to its environment, the blood pressure changes, the heart rate increases or decreases depending on the activity, and the body adapts and regulates its internal temperature and organ functions. The body normally exists in a regulatory state and only activates its fight or flight pattern in times of extreme stress.
Effects of Epinephrine
According to Dr. Michael King of Indiana University School of Medicine, epinephrine affects the peripheral nervous system with stimulating and inhibition. Epinephrine affects the central nervous system by enhancing respiration and increasing muscle activity. This chemical hormone stimulates smooth muscle cells and blood vessels in organs and tissue throughout the body. Epinephrine increases heart rate and enhances the force of muscle contractions. Epinephrine is also part of the endocrine systems' regulation of insulin.
Lecture notes from UMBC of Maryland indicate that epinephrine and norepinephrine are non-steroidal secondary message system hormones from the medulla excreted from the adrenal glands. During exercise, the body utilizes epinephrine and norepinephrine. Len Kravitz, Ph.D., "Exploring the Mysteries of Exercise," examines the role of these two chemical hormones on the body during exercise. Dr. Kravitz notes that when a person exercises regularly, epinephrine and norepinephrine work more effectively when the body is at rest. Although this is not a new idea, he states that the body burns more fat during exercise because epinephrine mobilizes fat molecules to activate muscle energy. When a person exercises he allows this adrenalin pumper to use energy more effectively.
- Voet, Donald and Voet, Judith. Biochemistry. 2nd Edition
- Elmhurst College: Adrenergic Drugs
- Indiana University School of Medicine, Michael W. King, Ph.D: Biochemistry of Neurotransmittors
- Adapted from G.H. Bell, J.N. Davidson, D. Emslie-Smith. 1972. Textbook of Physiology 8th edition. Livingston, Edinburgh, p 868 in: Ch. 16
- UMBC Maryland: Endocrine system