Adrenaline is one of the most important hormones for humans. Without it, the normal functioning of the body is impossible. Medicine is widely used drugs based on adrenaline. Let's figure out what kind of hormone it is.
General information
This hormone is known in the post-Soviet space under the name "Adrenaline", but for Europeans and residents of both Americas, it is better known as Epinephrine. It is the main hormone of the adrenal medulla. Also plays a role neurotransmitter - a special substance produced by the body for the normal transfer of electrochemical impulses from nerve cells (neurons) to muscles, from neuron to glandular cell or from one nerve cell to another.
Adrenaline belongs to the group catecholamines - active substances that are intermediaries in the implementation of chemical interactions in biological organisms. Catecholamines regulate these processes. They are present in all tissues of the body. Their function is especially important in regulating the work of the nervous system.
Functions of adrenaline
Epinephrine is a fight-or-flight hormone. Its synthesis increases dramatically in threatening or stressful situations. A large release of the hormone into the blood is observed in shock, trauma, and the presence of burns. Muscular work also helps to increase the secretion of adrenaline.
Like any other hormone, adrenaline affects the body indirectly - it affects the tropic (sensitive) receptors to it (adrenergic receptors such as α- and β):
- Alpha-1 adrenergic receptors are located in smooth muscle fibers, the ciliary muscle of the iris. Their stimulation leads to pupil dilation and vasoconstriction, which leads to an increase in blood pressure;
- Alpha-2 adrenergic receptors are located in the thickness of the muscular wall of blood vessels. Their excitement leads to vasoconstriction and an increase in blood pressure;
- Beta 1 adrenergic receptors are located in the thickness of the heart muscle. Adrenaline, by stimulating them, increases the heart rate and strength of the heart;
- Beta 2 adrenergic receptors are located in the uterus, bronchioles, liver. When exposed to epinephrine, the production of norepinephrine, which leads to the expansion of the respiratory tract, the synthesis of glucose from liver glycogen is enhanced;
- Beta 3 adrenergic receptors have been found mainly in adipose tissue. In the case of their stimulation with adrenaline, fat is intensively broken down and energy is generated.
Epinephrine is a catabolic hormone that enhances the breakdown of complex substances into simple ones with the formation of energy. It increases blood sugar levels and enhances tissue metabolism.
As a counterinsular (having effects opposite to insulin) hormone enhances synthesis processes glucose, inhibits the formation of glycogen in striated muscles and liver, improves the absorption of glucose into tissues.
In the presence of a high concentration of adrenaline in the blood, an increase in protein breakdown processes is observed.
The hormone affects striated muscles. With prolonged exposure to moderate concentrations, an increase in cardiac muscle and skeletal muscle is observed. This affects the adaptive processes to prolonged stress and prolonged physical stress. But in high concentration, adrenaline, leading to the breakdown of proteins, leads to a decrease in muscle mass and strength, and weight loss. This explains the loss of weight, to the point of exhaustion, with prolonged stress.
Epinephrine stimulates the central nervous system. Thanks to this hormone, the level of mental energy increases, a feeling of cheerfulness arises, and orientation on the terrain and in a specific situation improves.
By affecting the hypothalamus, the hormone leads to an increase in the production of cortisol. As a result, there is an increased resistance to shock and stress.
This hormone has a strong anti-inflammatory and anti-allergic effect. Due to the inhibition of the secretion of hormones such as serotonin, histamine, a number of biologically active substances, a decrease in the sensitivity of body tissues to these substances is observed. As a result, the body's response to the allergen is reduced. This effect is especially important in the relief of acute allergic reactions.
Under the influence of epinephrine, the number of white blood cells (leukocytes) increases, largely due to their release from the spleen and redistribution of blood cells during vasospasm.
Stimulates the blood coagulation system. Under its influence, the number increases and the functional activity of cells such as platelets increases. Together with spasms of small vessels, this leads to a reduction in bleeding time.
Reduces blood flow to the corpus cavernosum when the hormone is injected into them. The mechanism of action is due to the effect on alpha-receptors to adrenaline.
Phases of the hormone's effect on the body
The most important effect of adrenaline on the human body is the effect on blood pressure. Let's take a closer look at the mechanism of the hormone's influence on blood pressure.
In the mechanism of the hormone's effect on blood pressure, four periods are distinguished:
- Cordial. It is associated with an exciting effect on Beta-1-adrenergic receptors. It manifests itself in the form of an increase in the systolic component of blood pressure due to an increase in cardiac output.
- Vagus (effect on the vagus nerve). It is associated with a stimulating effect on baroreceptors (receptors that respond to pressure changes) of the aortic arch and the receptors of the same name of the carotid glomerulus by increased release of blood into the systolic phase. There is an activation of the dorsal nucleus of the vagus nerve, triggering a baroreceptor depressor (oppressive) reflex. There is a decrease in the frequency of heart contractions and a short-term cessation of the rise in blood pressure.
- Pressor (literally - increasing) vascular. The pressor effects of epinephrine are stronger than the vagal ones. It is observed with stimulation of Alpha-1 and Alpha-2-adrenergic receptors. It manifests itself in the form of a further increase in pressure. Adrenaline also affects the kidneys. As a result of a cascade of reactions in the kidneys, a significant rise in blood pressure is observed.
- Depressive vascular. Directly depends on the degree of excitation of the beta-2-adrenergic receptors of the vascular wall. It is accompanied by a drop in blood pressure. These receptors are influenced by adrenaline for the longest time.
Briefly about the effect on the body
Based on the above, we can briefly describe the effect of the hormone on the body, depending on the receptors tropic to it.
| Alpha adrenergic receptors | Beta-adrenergic receptors |
|---|---|
| Leads to spasm of blood vessels (spasm is most pronounced in the vessels of the intestines, skin, kidneys, coronary vessels) | Leads to dilation of blood vessels (especially in skeletal muscle, coronary vessels, liver vessels) |
| Leads to mydriasis - a contraction of the ciliary muscle of the eye | Increases the frequency and strength of heart contractions |
| Leads to contraction of the constricting muscles (sphincters) of the digestive tract | Reduces the tone of the bronchial muscles |
| Leads to contraction of the splenic capsule | Reduces bowel motility and tone |
| Leads to contraction of the muscular layer of the uterus | Enhances the formation of glucose and the breakdown of fats |
Synthesis of adrenaline in medicine
In medicine, adrenaline is used due to its pronounced physiological properties. It belongs to the group of adrenergic agonists. In practice, preparations of epinephrine salts are used - hydrotartrate and epinephrine hydrochloride.
In most cases, drugs are used as vasoconstrictor, hypertensive drugs (drugs that increase arterial pressure), bronchodilator (expand the lumen of the bronchi), hyperglycemic (increase blood glucose levels) and antiallergic agents. Agents based on adrenaline are widely used for violations of the cardiac conduction system in cases of the development of acute conditions. For example, with myocardial infarction.
With the introduction of solutions of this hormone at a rate of 0.04-0.1 micrograms per kilogram per minute, it enhances and speeds up the heart contraction, leads to an increase in the stroke volume of blood flow and the volume of minute blood flow, leads to a decrease in peripheral vascular resistance.
When using the drug in a dosage greater than 0.2 micrograms per kilogram per minute, vasoconstriction and an increase in blood pressure are observed (mainly due to systolic component). Possible short-term reflex bradycardia (decreased heart rate).
The effect after administration of the drug is observed in the shortest possible time when administered intravenously (the effect lasts no more than 2 minutes). When administered subcutaneously, the effect appears after 3-8 minutes, and its maximum manifestation is observed after 15 minutes. When the drug is injected into the muscle, the onset of the effect varies.
Due to its ability to constrict blood vessels in the thickness of the skin and mucous membranes, and its ability to reduce blood flow, epinephrine is widely used for local anesthesia. Thanks to adrenaline, anesthetics last much longer.
So in what situations are adrenaline drugs used? The main indications for the use of these medicines are:
- allergic reactions of an immediate type. They develop with the use of medicines, medical sera, in cases of blood transfusion, when eating food, in cases of insect bites;
- with bronchial asthma to stop an attack, with bronchial spasm;
- in cases of cardiac arrhythmias;
- with bleeding;
- with a drop in blood pressure that does not respond to fluid replacement therapy;
- with attacks of hypoglycemia due to inadequate insulin therapy;
- during eye surgery.
