The vasoconstriction It is the reduction of the caliber of a blood vessel due to the contraction of the vascular musculature that makes up the walls of the arteries, arterioles and veins. Capillaries - very small blood vessels - do not have muscles in their walls, so they do not enter into the concept of vasoconstriction.
This reduction in vascular caliber occurs for many causes and also has multiple purposes. The control of contraction and relaxation of the vascular muscles depends on many intra and extracellular phenomena, and any alteration of these can cause pathological events such as arterial hypertension, ischemia and heart attacks..
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Peripheral vasoconstriction is an important autonomic response of the body to specific stimuli.
This phenomenon occurs basically in the presence of hypothermia and severe bleeding; in the first case, to try to maintain the proper body temperature; and in the second case, to preserve blood supply to key organs.
When there is a picture of hypothermia, either by contact with very cold water or exposure to climates with freezing temperatures, the sympathetic nervous system is activated and orders the adrenal glands to release certain substances, such as adrenaline and norepinephrine, which have a powerful vasoconstrictive effect at the peripheral level.
These substances act at the level of certain receptors found on the walls of blood vessels..
Once these receptors are activated, the muscle cells of the arteries and arterioles contract, reducing their lumen or caliber, at the same time reducing the flow of blood through them and diverting it to the vital organs..
This mechanism is activated when the core body temperature drops, not the skin temperature. That is why prolonged exposures to cold or extremely low temperatures are necessary for peripheral vasoconstriction to occur as such, with the consequent redistribution of blood flow.
When major bleeding occurs, whether it is simple or injury-mediated, vasoconstriction also occurs.
Simple bleeding is understood as that which is not a consequence of tissue destruction, such as digestive bleeding or dysfunctional uterine bleeding. Bleeding from musculoskeletal injuries is usually more severe.
The sympathetic nervous system is activated by perceiving the loss of blood and the decrease in blood pressure. Vasoconstrictive substances are released, which exert their functions by increasing peripheral vascular resistance, blood pressure and ensuring blood flow to the heart, brain and lungs, compromising the kidneys and intestines..
This vasoconstrictor effect has a limited action, both in time and intensity, both due to the consumption of the substances that generate it and due to their definitive consequences, since prolonged blood flow compromise can cause renal necrosis and mesenteric infarcts, deteriorating the condition. patient clinic.
Cutaneous vasoconstriction is not a phenomenon apart from the peripheral one, but it has features of its own. The main characteristic of cutaneous vasoconstriction is paleness.
By reducing the caliber of the arterioles and small vessels of the dermis, with the immediate reduction of blood flow, there is an abnormal loss of skin color and hypothermia to the touch.
Paleness, considered a clinical sign by doctors in general, is usually one of the first obvious consequences in patients with active bleeding or hypothermia..
In fact, its onset is very early and allows health professionals to act before further complications occur..
Some particular situations other than cold or bleeding can trigger skin vasoconstriction. Stress, the use of certain medications or drugs, sports activity and various diseases can cause paleness by different mechanisms, the only common denominator being the entry of calcium into vascular muscle cells..
The factors that trigger vasoconstriction can be endogenous or exogenous. Whatever its origin, multiple internal elements will mediate so that the final consequence is the reduction of the vascular caliber.
Also known as adrenaline (perhaps its most popular name), it is a natural substance permanently present in the blood and that produces a vasoconstrictor effect when its serum levels increase..
Chemically very similar to epinephrine, but with a more powerful vasoconstrictor effect. It is only released from the adrenal glands in very precise situations.
It is also known as norepinephrine. Some authors refer to norepinephrine when they speak of the naturally produced one and norepinephrine when they speak of the synthetic.
Synthetic form of antidiuretic hormone produced in the pituitary gland. In addition to concentrating the urine by promoting the renal reabsorption of water, it has an important vasoconstrictor effect.
Dopamine is an organic catecholamine produced in the brain and kidneys that performs multiple functions in the human body, including vasoconstriction tasks..
These first four substances are produced naturally by the body, but they can also be synthesized in pharmacological laboratories..
All have clinical use and are frequently used in intensive care units, trauma shock and operating rooms..
Potent endogenous vasoconstrictor, whose activation is inhibited through the regular administration of drugs known as ACEIs (angiotensin converting enzyme inhibitors), which are one of the most widely used antihypertensives in the world today.
Endogenous substances that act in the area of the vascular muscles, favoring the entry of calcium into the muscle cells and generating vasoconstriction.
Some chemical substances produced in laboratories, clandetine or not, that are used for recreational purposes, have a predominantly peripheral vasoconstrictor effect and can be administered by different routes. Among these substances we have:
- Cocaine.
- Amphetamines.
- Alpha-methyltryptaline (Indopan).
- 25I or "N-Bomb".
- LSD.
- Mephedrone (meow meow, cactus food, CatMef).
Several drugs have some vasoconstrictive effect, not necessarily as their main function, but that affect blood pressure values. The most recognized are:
- Ephedrine.
- Pseudoephedrine.
- Phenylephrine.
- Oxymetazoline.
- Antihistamines.
Caffeine and xanthines, present in coffee and various types of tea, can cause asymptomatic vasoconstriction in humans.
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