Vasodilation: what it is, how it works, and what it is for

The circulatory system is a transport system that living beings use to move within our organism nutrients, metabolic compounds, oxygen, carbon dioxide, hormones and many others substances. Through this system of veins, arteries and capillaries flows blood, a reddish liquid whose hue is attributable to red blood cells, which carry oxygen to each and every cell in the body. body.

An adult human being has approximately 5,000,000 red blood cells per microliter of blood, that is, 1,000 times more than the proportion of white blood cells. In addition, from end to end (and counting veins, arteries and capillaries), our circulatory system would occupy about 100,000 kilometers in a straight line, 2.5 times the earth's circumference. As you can see, this transport network moves in astronomical numbers.

Beyond the importance of the circulatory system, the energy expenditure of the heart, heart disease and its impact on society and many other topics of an informative nature, there is a term referring to the circulatory system that not everyone knows.

We tell you everything about vasodilation and what it implies at a physiological level.

• Related article: "Autonomous Nervous System: Structures and Functions"

What is vasodilation?

Vasodilation is a process in which the diameter of the blood vessels increases (veins or arteries), after which a more hollow cavity is formed and allows greater blood flow. This concept is contrary to that of vasoconstriction, an event in which the vessels are narrowed by the action of small muscles in their walls.

The Clínica Universidad de Navarra (CUN) provides a much more exact definition of the term at the medical level: “A dilation of the lumen of the blood vessels, either as a consequence of a increased intravascular pressure (passive vasodilatation), or, more frequently, by a decrease in vasomotor tone, as a consequence of the relaxation of the vascular muscles”.

Generally, vasodilation has a positive connotation and vasoconstriction is associated with pathological processes.. This is mainly because vasodilation commonly occurs in response to natural events, such as low blood glucose levels. oxygen in the organism or an increase in body temperature (physiological processes that occur in the performance of sports, for example).

• You may be interested in: "The 7 differences between arteries and veins"

When does vasodilation occur?

There are multiple causes for which vasodilation can occur in the body. Among them, we find the following:

• Exercise: As the diameter of the vessels expands, more blood flows, allowing more oxygen and nutrients to reach the muscles during times of activity.
• Alcohol: these types of drinks are natural vasodilators. Interestingly, as more blood reaches the skin, it is common to feel a sensation of heat when drunk.
• Inflammation: inflammatory processes occur in response to physiological stress from a blow or bacteria, among others. This induces local vasodilation.
• Natural chemicals: some hormones, such as histamine, are natural vasodilators in the body.
• After the consumption of vasodilators: some drugs that we will address in later lines.

As you can see, vasodilation generally has a specific purpose: to increase blood flow to an area that requires more oxygen, nutrients, or cellular action.

The case of inflammation is especially striking, since it makes great biological sense to widen the diameter of veins and capillaries to allow greater blood flow. to the affected area. Macrophages and mast cells, cells of the immune system that generally respond to attacks by Pathogens, by acting locally, cause fluid to leak out of the blood into the tissues, generating a edema.

The process of alcohol consumption is also very interesting. These drinks, at the level of the circulatory system, increase cardiac activity and produce vasodilation peripheral, which explains the reddening of the skin and the increase in superficial temperature after consumption.

Curiously, this does not help to resist the cold more, since a greater superficial blood flow implies a higher heat loss. Medical portals therefore stipulate that there could be an increased risk of hypothermia after alcohol poisoning in an exceptionally cold environment.

spontaneous vasodilation

Spontaneous vasodilation of a tissue implies a rapid response of the same to a stimulus, in order to obtain a greater required blood flow. Strong emotions, such as joy, despair, or fear, lead to more work for the heart to pump blood.. As a consequence, vasodilation is activated to give rise to a more consistent and strong blood flow.

Have you ever wondered why we turn red when we make a mistake? When the human being feels that he has done something wrong or blushes for any other reason, the parasympathetic system is activated and adrenaline is released throughout the bloodstream. This causes increased heart rate, shortness of breath, increased sweating, and characteristic vasodilatation in the facial area. Therefore, as there is a greater flow of blood under the skin, it is said that the person has blushed (literally, there is a greater flow of blood).

Vasodilation and temperature

It is known to every biologist that vasodilation is an excellent regulatory mechanism in all animals with a blood system. When it is very hot, the superficial thermoreceptors send the signal to the brain that something must be done to dissipate heat.

For this reason, a process of vasodilation is activated, which allows blood to flow to the outermost layers of the skin. This promotes a thermal exchange with the environment, which helps the individual to lower their body temperature.

If you look at a fennec (desert fox), you will see that it has ears that are inordinately large in comparison to the rest of its body. This characteristic is not anecdotal: in addition to excellent listening, it gives the animal greater superficial irrigation, which allows heat to be dissipated during the hottest times of the day. Fascinating, right?

• You may be interested in: "Circulatory system: what it is, parts and characteristics"

Diseases associated with this physiological process

Although we have previously said that vasodilation is usually associated with health, this is not always the case. Here are some diseases that are relatively related to this physiological event.

shock

Shock has several causes: low blood volume in the body, inadequate cardiac pumping capacity, and excessive widening of the blood vessels, or what is the same, vasodilation (also known as shock distributive).

If it is exaggerated, the dilation of the blood vessels can reduce the pressure. This, in some cases, leads to a decrease in blood flow and a lower supply of nutrients and oxygen to certain tissues of the body. Blood vessels can become excessively dilated for reasons such as these:

• An allergic reaction or bacterial infection of a serious nature.
• Vasodilator drug overdose.
• Spinal cord injuries.
• Certain endocrine disorders.

Low blood pressure (hypotension)

This event is closely linked to the previous case. When blood pressure is much lower than normal, the patient may experience a severe deficit on a physiological level.. This causes the individual nausea, dizziness, confusion, discomfort and even loss of consciousness.

Hypotension can cause the previously described shock if it occurs pathologically, so a quick medical approach is sometimes necessary. This includes giving blood through an IV, medications to increase blood pressure and heart strength, and other drugs.

vasodilators

Vasodilators, as their name suggests, are drugs that widen (vasodilate) blood vessels. These act directly on the muscles of the walls of veins and arteries, preventing them from contracting and the diameter of the space from decreasing. As a result of the administration of these drugs, blood flows more easily through the tubes, which prevents the heart from pumping as fast, thus lowering high blood pressure.

Doctors often prescribe the use of vasodilators in the following scenarios: high blood pressure (usually or during pregnancy and childbirth), heart failure and pulmonary hypertension, among other clinical pictures.

In any case, the use of vasodilators is not without risk. Medical portals report that they report certain side effects, such as an increase in the rate of heartbeat (tachycardia), palpitations, nausea, vomiting, flushing, headache and many other signs clinical. For this reason, their consumption is only considered when a medical professional has prescribed them for a specific reason.

Summary

Vasodilation is a normal physiological process, as it occurs when we are nervous, when exercising, when the temperature rises, with the consumption of alcohol and in many other common events during the individual's lifetime.

Unfortunately, there are certain pathological processes that can arise in response to excessive vasodilation. Hypotension can cause not enough blood and oxygen to reach the brain and other organs of the body, which can be life-threatening.

Bibliographic references:

• Shock (Shock), MSD manuals. Collected on January 31 in https://www.msdmanuals.com/es/hogar/trastornos-del-coraz%C3%B3n-y-los-vasos-sangu%C3%ADneos/presi%C3%B3n-arterial-baja-y-choque-shock/choque-shock#:~:text=La%20dilataci%C3%B3n%20excesiva%20de%20los, from%20ox%C3%ADgeno%20to%20the%20%C3%B3organs.&text=The%20mechanisms%20by%20the%20that%20these%20diseases%20produce%20vasodilatation%C3%B3n%20are%20varied.
• Vasodilation, University of Navarra Clinic. Collected on January 31 in https://www.cun.es/diccionario-medico/terminos/vasodilatacion
• Vasodilators, Mayoclinic.org. Collected on January 31 in https://www.mayoclinic.org/es-es/diseases-conditions/high-blood-pressure/in-depth/high-blood-pressure-medication/art-20048154