Autonomous Nervous System: Structures And Functions
Throughout our lives we perform a large number of actions. We run, we jump, we talk…
All of these acts are voluntary elements that we do voluntarily. However, also We do a lot of things that we are not even aware of, many of which in fact are what keep us alive and with the possibility of doing things voluntarily, such as the control of heart and respiratory rates, the acceleration or deceleration of physiological systems or digestion.
At a neurological level, these two types of actions are carried out by two differentiated systems, with conscious actions being carried out by the somatic nervous system. and the unconscious ones by the autonomic nervous system
The autonomic nervous system, also called the vegetative nervous system, is one of the two divisions that have been made of the nervous system at a functional level. This system It is responsible for connecting the neurons of the central nervous system with those of the rest of the body systems and organs, forming part of both the central and peripheral nervous systems. Its basic function is the control of the internal processes of the organism, that is, the viscera, the processes governed by this system being foreign to our will.
The connections with the different target organs of this system are both motor and sensory, with both efferents and afferents. It is therefore a system that sends information from the parts of the brain to the organs, causing a specific reaction or action in them while at the same time it recaptures information about its state and sends it to the brain, where it can be processed and acted accordingly. . Despite this, in the autonomic nervous system the presence of efferences predominates that is, its function is mainly to emit signals in the direction of the organs.
The neurons of the autonomic nervous system that connect with the various organs of the body generally do so through the ganglia, having pre and postganglionic neurons The action of the preganglionic neuron is always due to the action of acetylcholine, but in the neuron that interacts between the ganglion and the target organ, the hormone released will vary depending on the subsystem (acetylcholine in the parasympathetic nervous system and norepinephrine in the sympathetic nervous system). .
The autonomic nervous system is one of the most vital systems to keep us alive, mainly due to the function it performs.
The main function of this system is the control, as we have previously indicated, of unconscious and involuntary processes, such as breathing, blood circulation or digestion. It is responsible for keeping the processes of the internal organs and viscera in shape and activated while allowing the detection and control of internal problems.
It also prepares us to face specific situations mediated by the environment, such as the secretion of saliva or digestive enzymes at the sight of food, activation in the face of possible threats or the deactivation and regeneration of the system through rest.
Any organism with the complexity of vertebrate animals needs a complete nervous system, with a central nervous system and peripheral nervous system, to coordinate the different parts of the organism. And among invertebrates we also find simple nervous systems, and other complex ones, like that of the octopus. This is because among animals it is necessary to adapt to changes in the environment quickly, by moving, unlike fungi and plants.
What controls the autonomic nervous system?
As part of the nervous system responsible for controlling the correct unconscious visceral functioning, the autonomic or vegetative nervous system is innervating most organs and body systems, with the exception of the muscles and joints that govern voluntary movement.
Specifically, we can find that this system controls the smooth muscles of the viscera and various organs such as the heart or lungs It also participates in the synthesis and expulsion of most secretions to the outside of the body and part of the endocrine secretions, as well as in metabolic processes and reflexes.
Some of the organs and systems in which this system participates are the following.
The autonomic nervous system governs pupil opening and the ability to focus your gaze connecting with the muscles of the iris and the entire eye.
2. Heart and blood vessels
Heartbeat and blood pressure They are fundamental elements for the human being, which are governed unconsciously. In this way, it is the vegetative nervous system that is responsible for regulating these vital elements that keep us alive second by second.
3. Lungs
Although we are able to control our breathing to a certain extent the act of breathing continuously is not conscious, just as as a general rule neither is the rate at which we need to inhale. Thus, breathing is also partially controlled by the autonomic nervous system.
4. Digestive tract
Through food, humans are able to acquire the various nutrients that the body needs to continue functioning. Although the behavior of eating is consciously controlled, the process by which the digestive tract transforms the food and acquires the necessary components from it is not, being the set of actions that the body carries out during digestion involuntary and governed by the autonomic nervous system.
5. Genitals
Although the sexual act itself is carried out consciously, the set of elements and physiological reactions that allow it to be carried out are fundamentally controlled by the autonomic system, which governs processes such as erection and ejaculation Furthermore, these processes are complicated when a feeling of fear or anxiety is experienced, something that links it to various physiological states.
6. Secretion of enzymes and waste
Tears, sweat, urine and feces are some of the substances that the body expels into the environment. Its secretion and expulsion is due and/or can be altered in part due to the functioning of the autonomic nervous system The same occurs with the secretion of digestive enzymes and saliva.
Parts of the autonomic nervous system
Within the autonomic nervous system we can find a series of subdivisions of great importance, which perform differentiated functions Specifically the sympathetic and parasympathetic nervous systems stand out which perform opposite functions in order to allow the existence of a balance in the activity of the organism.
A third system can also be found, the enteric system which is mainly responsible for the control of the digestive tract.
Being one of the divisions of the autonomic nervous system, the sympathetic system is responsible for preparing the body for action, facilitating the fight or flight response to threatening stimuli. To do this, it produces an acceleration of some body systems and inhibits the functioning of others, spending a lot of energy in the process.
The mission of this part of the autonomic nervous system is to prepare the body to respond quickly to risk situations, deprioritizing certain biological processes and giving them to those that allow us to react quickly. That is why its function has ancestral characteristics, although that does not make it any less useful; It adapts to modern life situations and can be activated by relatively abstract ideas, such as the certainty that we will be late for a business meeting.
2. Parasympathetic nervous system
This branch of the autonomic nervous system is the one that is responsible for returning to a state of rest after a period of great energy expenditure It is responsible for regulating and slowing down the body, allowing energy to be recovered while allowing the functioning of various systems. In other words, it is responsible for the regeneration of the organism, although it also intervenes in the generation of orgasm, something that does not seem to have much to do with the rest of the functions with which it shares biological roots.
3. Enteric nervous system
Although the parasympathetic nervous system also has a clear influence on the digestive tract, there is a subdivision of the autonomic nervous system that specializes almost exclusively in the system by which we incorporate nutrients into our body. This is the enteric system, which innervates the digestive tract and regulates its normal functioning.
As it is in charge of one of the most important systems for survival, the enteric nervous system has to be fundamentally automatic, and constantly worry about maintaining the biochemical balance that exists in the different environments of the organism, adapting to the alterations that may occur depending on what is ingested, the state of activation, the hormones that circulate in the blood, etc.
