Sympathetic nervous system: characteristics and functions

Introducing ourselves to an opposition, reacting to a car that comes at us, discovering that the alarm has not gone off in the morning, escaping from someone who bothers us or threatens us… All of these Situations characterized by stress, anxiety or a clear sense of danger are regulated for that very complex and fascinating structure: the sympathetic nervous system.

In our daily life, We are barely aware of the large number of situations in which this structure operates. It is not necessary for a real or tangible risk to occur before us.

Factors such as daily stress or the mere pressure that usually almost implicitly accompanies each of our days reflect something admirable: We are organisms designed to make our way, to survive.to have under control (or at least try to) those elements of our environment that are significant.

Thus, situations as common as run to catch the subway and not be late for work, react in time so that cup does not fall on the floorso that our cat does not escape through the door or our child does not put that dangerous thing in his mouth are examples of the importance of said structure.

What we experience in those moments is also well known to us. The heart races, our muscles tense and we are able to perform movements very quickly in a matter of seconds. This entire physiological process in the face of any stimulus and situation with a high emotional connotation is orchestrated by this system. Let’s see more data below.

What is the sympathetic nervous system?

The sympathetic nervous system is one of the branches of the autonomic nervous system.. Let us remember, first of all, that we are dealing with a type of structures that are responsible for a large number of involuntary functions. That is, tasks such as heart rate control, digestion, sweating, etc. They are dimensions that regulate both the sympathetic, parasympathetic and enteric nervous systems.

However, The sympathetic nervous system is responsible for a series of very specific tasks: regulating and activating our reflexes and reactions.. It is, as we have already indicated, that organic center that allows us to react to any “non-neutral” emotional stimulus. As is, for example, any situation of stress, whether mild or intense, as revealed by a study carried out by the Welfare University in Osaka. In turn, It is made up of a chain of 23 ganglia that start from the medulla oblongata and that connect to both sides of the spinal cord and to the organs they innervate. On the other hand, This system is made up of two types of neurons. The first are the preganglionic cells, which connect with the spinal cord and the ganglion itself. Thus, in order to carry out their functions they need a very specific neurotransmitter: acetylcholine. For its part, The other type of neuron that governs the sympathetic system is the postganglionic neuron.which needs noradrenaline to be able to communicate between the ganglion and the organ it innervates (heart, liver, stomach, intestines, lungs, etc.)

Areas of the sympathetic system

On the other hand, it is important to know how the sympathetic system is structured. We know how it is connected, now let’s see how it is distributed:

Departure area: The sympathetic system starts, as we have pointed out, from the medulla oblongata, a nucleus that regulates a wide spectrum of functions that are unconscious to us, but vital for our existence.The cervical sympathetic area, where all the nervous formation of the head and neck are located.Upper cardiac area, with all the visceral vascular branches related to the carotid plexuses, the submandibular area, the pharynx, larynx, etc.The thoracic sympathetic area: a region encompassing each side of the spine, including joints, intercostal nerves, etc.The lumbar areaincluding the psoas muscle, inferior vena cava, etc.Pelvic areawhich runs from the areas of the sacrum to the rectum.

What happens in your body when the sympathetic nervous system is activated?

For anyone who suffers from stress in their daily lives, it will be of great interest to know what happens in their own body in these situations.. What’s more, if we suffer from something as common as hypertension, it may also be relevant to know how the sympathetic nervous system mediates in this case in relation to our health. In fact, studies such as the one carried out in Journal of Human Stress They explain to us how this bond is formed and what differences even exist between men and women.

Now, the mechanism of action of the sympathetic system in any situation of danger or anxiety is one of the most complex and striking processes. Let’s see as a diagram how he reacts to a threatening stimulus:

It promotes the release of adrenaline and norepinephrine into the blood through the kidneys. The purpose of this is simple: we need more energy and activation to be able to react, and that energy requires, for example, the liver to produce more glucose.Increases heart rate to provide us with more oxygen and nutrients through the blood.Bronchodilation occurs That is, we need more oxygen and our lungs work at maximum performance.All activities related to digestion slow down. We cannot forget that this process requires great energy and in times of stress and alarm, this task is secondary. The only thing the brain wants is for us to react, to confront that stimulus or to flee. At the same time, and no less interesting, The sympathetic system produces mydriasis or pupillary dilation. In this way, this unconscious reaction allows us to increase our visual field and react more safely.

Effects of the sympathetic system on different parts of the body

Eye: Sympathetic activation causes the radial muscle of the iris to contract.

Heart: the sympathetic causes an increase in heart rate.

Lungs: Bronchodilation and decreased lung secretions occur to allow greater air flow.

Stomach and intestines: It decreases motility and contracts the gallbladder.

Pancreas: It decreases both enzyme and insulin secretion.

Urinary bladder– Relaxes the detrusor muscle and contracts the urethral sphincter to help stop urine production.

Kidney: increases renin secretion to increase intravascular volume.

Other functions of the sympathetic nervous system

The sympathetic system It is not activated only in dangerous situations, but participates in multiple physiological processes. An example of this is their participation in sexual activity. Well, it increases blood flow to the genitals in response to sexual arousal, causing ejaculation in men and orgasm in both sexes.

However, When it comes to a stressful or threatening situation, the sympathetic system will be responsible for avoiding sexual activity.. For example, in the case of men, vasoconstriction of the circulatory system occurs, filling the penis with blood. This will prevent erections from occurring while fleeing or fighting.

Consequences of alterations in the sympathetic nervous system

The constant activation of the sympathetic system can have long-lasting effects on our body and cause chronic stress. In addition, Continuous surges of adrenaline can damage blood vessels and arteries, which in turn can raise blood pressure and increase the risk of strokes and heart attacks.

On the other hand, if this system does not work correctly, it can also cause problems for us. For example, We may not have the right responses in times of stress. We may not recognize that a danger exists and, as a result, we take more risks.

If our organs do not receive fight or flight signals, we will not be able to prepare for dangerous situations, due to the lack of blood pumping around our body. Autonomic dysfunction is a condition in which the autonomic nervous system and its divisions do not function properly. This can lead to altered functioning of the heart, sweat glands, pupils, and blood vessels, depending on the condition. Autonomic dysfunction can develop when the nerves of the autonomic nervous system are damaged and can range from mild to life-threatening.

The parasympathetic nervous system

To fully understand what the sympathetic nervous system consists of, it is important to take into account the functions of the parasympathetic nervous system.

The activation reactions caused by the sympathetic system will later be combated by the parasympathetic system.thus achieving a homeostatic balance that keeps the body in an optimal state of functioning, according to the stimuli of the external environment.

That said, the parasympathetic nervous system, is intended to provide a relaxation response. Thus, it induces a slowing of heart rate, respiratory activity and a reduction in blood pressure. Likewise, it promotes digestive function and sexual appetite.

In conclusion, As the philosopher Henri-Frédéric Amiel said, our body is the perfect temple of nature. It is something that has been given to us, however, it is our obligation to take care of it and also study it. Only in this way can we come to understand ourselves better, to understand why we are the way we are and why certain problems or conditions arise when we least expect it.

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