The sympathetic nervous system regulates the involuntary physiological reactions that are awakened in the face of danger and culminate in the experience of stress.
Stress is an emotion that, although unpleasant, is fundamental to our survival. It appears in situations that we perceive as harmful to our physical, psychological and emotional integrity, whether they are potentially dangerous or simple annoyances.
There is a part of our nervous system that, although little known in popular culture, is responsible for us feeling stress: the sympathetic system. Thanks to this subdivision of the autonomic nervous system our body prepares for those situations in which we need to issue a quick and effective response in order to survive.
Next we will see in depth what is the involvement of the sympathetic system in stress and how this peculiar set of nerve cells performs different functions that, as a whole, give rise to a physiological episode associated with anxiety.
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What is the sympathetic nervous system?
The sympathetic system is a part of the autonomic nervous system that regulates involuntary functions. It is responsible for controlling our reflexes and unconscious reactions to stimuli perceived as dangerous, this particular system being the one behind our physiological reaction to stress and all the adaptive responses involved in manifesting this emotion.
Stress is a fundamental reaction for our survival, and also for that of animals with a developed central nervous system. This phenomenon appears as a response to a situation that we perceive as dangerous for our physical, mental and / or emotional integrity and to which, in order to get out of it successfully, we must respond without delay, either fighting or fleeing from it. In just thousandths of a second, several parts of our body are activated and become the recipients of all energy and attention, paralyzing other processes that are not necessary at that time.
It is thanks to the sympathetic system and its response in the form of physiological stress that when we see, for example, someone chasing us with a gun down the street, we start running without even realizing what we are doing. It is also thanks to this system that if we see that we are going to get a ball in the face or that we are going to drop a cup on the floor we act quickly, protecting ourselves in the first case and trying to save the container in the second.
Next we will review what position the sympathetic system occupies in our body within the extensive and complex structure that is the nervous system in general. In addition, we will see a little above how the various parts of the nervous system are related andhow the involvement of the sympathetic system in stress occurs.
The sympathetic system within the nervous system
Broadly speaking, the nervous system is the body’s extensive telecommunications network composed of a complex highway of billions of neurons that communicate information through electrical impulses and neurotransmitters. These impulses can go both to muscles of the body, where they do what the brain tells them, as well as to come from different organs and go to the brain itself, where they will be interpreted in the form of senses.
According to a morphological classification, the nervous system is divided into two: the central nervous system and the peripheral nervous system. The central one is composed of the brain (brain, brain stem and cerebellum) and the spinal cord, the first being responsible for creating and processing information and giving orders while the second is responsible for sending that information to the corresponding nerves. The peripheral is composed of the network of nerves that communicate the central nervous system with all organs and tissues of the body.
And it is here that we introduce a lesser-known classification that attends to the function performed by different parts of the nervous system: the somatic nervous system and the autonomic nervous system. The somatic is the set of neurons involved in all the functions and voluntary actions of the body, such as throwing a ball, writing or speaking. On the other hand, the autonomic nervous system encompasses all those actions that occur in our body involuntarily, without having deliberate control over them. This system is subdivided into three systems: the parasympathetic, the sympathetic and the enteric.
The parasympathetic system encompasses all those functions that make the organism at rest. It is this system that is responsible for reducing heart rate, maintaining active digestion, reducing blood pressure, contracting the pupils … On the other hand, the sympathetic does just the opposite, leading the body to its physiological activation: it increases the heartbeat, inhibits digestion, increases blood pressure and dilates the pupils … In short, it does everything possible to keep the body activated and prepare its energies to face a possible threat. It causes us stress.
The other subsystem that is within the autonomous is the enteric, which although it is not the subject of this article, it is important to mention it since it is this system that is responsible for a very important function for us to live: allow the movements of the gastrointestinal system.
Why does it lead to stress experience?
As we have just seen, the sympathetic nervous system is a part of the nervous system that is responsible for involuntary responses to different stimuli, specificallyactivating the body to prepare for a situation from which it will have to issue a fight or flight response. It is the sympathetic system that is behind the stress we manifest when we perceive a danger or something that is going to cause us some kind of harm or discomfort.
Being a functional subdivision of the nervous system, the sympathetic cannot be anatomically isolated as we could with the central and peripheral systems. In fact, the sympathetic system is rather a set of reactions and nerve centers that are related and found in those two anatomical nervous systems, doing activities that both systems are responsible for.
What should be clear about the sympathetic system is that it is fundamental for our survival and that it worksby intervening in the most primitive mechanisms available to our organism, acting quickly in situations in which time is pressing and it is necessary to invest all our energies to successfully get out of a difficult situation and that could be a damage, situations in which we feel stress. When the situation is not perceived as dangerous, this system is simply muted, not working.
At the moment in which the sense organs send information to the brain and it interprets it as a signal that we are in a dangerous situation, the sympathetic system is quickly activated and its neurological centers take control. Thanks to its involuntary control we react to different stimuli without having to process that information, saving us time and cognitive effort. This is why we are often surprised how quickly we react in stressful situations, not because we think about them, but just the opposite, which is that we think rather little and instinctively.
The 5 main functions of the sympathetic nervous system
Finally, we will see what functions the sympathetic system performs, all of them related to the organic response that we manifest in a stressful situation. What should be clear to us about the following functions is that all of them imply that the organism responds in the most efficient way to danger, either by fleeing or attacking.
1. Production of stress hormones
The sympathetic system increases the production of stress hormones, especially adrenaline and noradrenaline. These hormones are what lead us to experience both physical and emotional stress, and are very important to promote all the functions carried out by this part of the autonomic nervous system.
In a dangerous situation, stress is necessary, since it is what motivates us to act. Once chemically induced, stress causes our physical and psychological performance to increase. However, this carries a negative part, especially if the state of stress is prolonged too much and is the long-term damage of being in constant tension.
2. Increased heart rate
When you have to act quickly in the face of a hazard, you need your muscles to be ready to work as efficiently as possible. For thisit is necessary that they receive all the oxygen and nutrients available, something that is achieved faster when the heart pumps blood very strongly and quickly.
Thus, the sympathetic nervous system causes the heart rate to increase to achieve this end, causing blood pressure to also increase. This is why when we are stressed we can feel tachycardia, palpitations and all kinds of sensations in the chest since the heart is working more than normal.
3. Dilation of the pupils
In a situation of danger, our senses have to be sharpened, especially that of sight, which is the one that humans use the most. The sympathetic system commands the eye muscles to dilate the pupils, causing more light to be captured. By dilating the pupils we capture as much visual information as possible, facilitating in turn a better response.
4. Acceleration of breathing
When we feel that we are in danger, it is normal for us to start breathing faster. The sympathetic system foresees that we will use the muscles to flee, knowing that more oxygen will be required so it gives the order to accelerate breathingto increase the volume of air we inspire.
5. Inhibition of unnecessary functions
As we have said, when you are in a situation of danger it is necessary todevote all your energies to mechanisms that help survival, be it fight or flight. Basically our energies must be invested in the muscles, the brain, the senses, the heart and the lungs, being the rest of the organs and their functions not necessary in this situation.
That is why the sympathetic system gives the order to stop any activity that involves an expenditure of valuable energy and that does not help survival, such as digestion, sweating and urine production. For this reason when we are stressed we get a knot in our stomach, we stop feeling that we feel like urinating or do not sweat, although it is true that there are people who just being stressed get on top of it.
Are you looking for psychological assistance to manage stress?
If you are interested in having professional help to learn how to better regulate stress and anxiety, contact me. I am a psychologist specialized in the cognitive-behavioral model with many years of experience offering my services to individuals and companies, and I attend face-to-face and also in online sessions by video call. You can find all contact information in my profile as an author.
To the classic question “what do you do?” I always answer “basically I am a psychologist”. In fact, my academic training has revolved around the psychology of development, education and community, a field of study influenced my volunteer activities, as well as my first work experiences in personal services.
