We know that the brain is the primary component responsible for controlling and managing all of the processes that take place in our body. But the truth is, other systems are also very important in maintaining it and have the potential to influence their business.
An example of this is the digestive system, through which we can get the nutrients we need to stay alive. The brain and the stomach are linked and communicate by nerve impulses and the transmission of chemicals.
Functional divisions of the nervous system
When we talk about the nervous system, we usually divide it into the central nervous system, in which we find mainly the brain and spinal cord, And the peripheral or autonomic nervous system, which would correspond to the set of ganglia and nerves which innervate the various organs and transmit information from the organs to the brain and vice versa.
Within the autonomic nervous system, we usually identify two basic subsystems, the sympathetic and the parasympathetic, Which are responsible for managing all the activities that the body performs outside of our consciousness and preparing our body to face dangerous situations (or to decrease activation after this situation).
however, there is a third subsystem of the autonomic nervous system, little studied and often overlooked despite its enormous importance for survival. It is the enteric nervous system, a part of our body linked to the fascinating phenomenon of the dialogue between the viscera and the brain.
The enteric nervous system
The enteric nervous system is of paramount importance for the survival of the organism. It is the set of nerve fibers that innervate and control the functioning of the digestive system. It controls aspects such as the movement of the muscles of the digestive tract which allow food to reach the stomach, the secretion of acids and enzymes which dissolve food, the absorption of nutrients and the expulsion of wastes.
this system it is made up of millions of neurons (In an amount similar to that of the spinal cord) distributed throughout the digestive tract and although it is influenced by the sympathetic and parasympathetic systems, it is controlled by the partially independent enteric ganglia, acting reflexively. Not in vain, the digestive system has sometimes been called the second brain.
In this system too a large number of hormones and neurotransmitters can be found (Particles that act as messengers between neurons), such as serotonin (most of which we have presented to our bodies are found and are synthesized in this system, although it is also produced by the brain), dopamine, substance P or GABA among many others.
These neurotransmitters are regulated by the enteric system itself, although there is influence on this system by those of the central system itself.
Stomach-brain nerve communication
Although it has some independence, the enteric system and the central nervous system are linked, and some nerves in the central nervous system are connected to different organs in the digestive tract.
The vagus nerve is the main means of nerve communication between the brain and the digestive system. This nerve is of great importance in different bodily systems; in the case of the stomach, it has been found that two-way communication takes place in which in fact the amount of information that goes from the stomach to the brain is greater than that which goes from the brain to the stomach .
That there is a greater transmission of information from the stomach to the brain than the other way around this is due to the need to control the intake. Eating behavior is governed by the brain, which causes the brain to receive information about the good or bad functioning of the digestive system or whether consumption is harmful or beneficial for us, as well as whether the level of consumption is excessive (feeling satiety and hunger).
Yet the lazy helps control bowel activity especially when the body is in a situation of tension or danger. In this situation, the sympathetic system helps to stop the functioning of the digestive system. When the dangerous situation passes, it is the vagus nerve which is mainly responsible for reactivating its functioning by acting at the parasympathetic level. It also participates in the emission of bile.
Moreover, while the enteric system is able to synthesize and manage neurotransmitters, it is also affected by brain function. Situations that generate stress or anxiety affect the enteric nervous system and their motility, as well as neurochemical imbalances such as those that occur during depression. Some of the hormones involved in this brain-digestive tract relationship are serotonin, norepinephrine, and dopamine. Also acetylcholine, this being important for example in the functioning of the vagus nerve.
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The role of intestinal flora in communication
In addition to the role of nerve conduction and neurotransmitters, the intestinal flora also has an effect in communication between the enteric nervous system and the central nervous system.
The microorganisms that inhabit our digestive tract have an influence when the enteric system signals the good or bad state of the system in the brain, by the modification of the secretion of neurotransmitters. Likewise, affects the functioning of the immune systemThis in turn generates an indirect effect on behavior and health status.
Various rodent research also reflects the functioning of the digestive system and intestinal flora and fauna. they can even have an effect on behavior by variations in the structure and function of the brain, modifying responses to certain neurotransmitters.
Effects of communication between the brain and the digestive system
The fact that the brain and the digestive system are connected is of great importance and has very relevant implications. And is there an influence of the digestive system on the brain function, and vice versa.
The presence of bowel disorders may be related to aspects such as anxietyAnd it has been shown that the presence of anxiety or depressive disorders can lead to worsening or even the appearance of digestive problems such as peptic ulcer or irritable bowel syndrome.
It has even been detected that some of the microorganisms that line our digestive system can generate antioxidant and anti-inflammatory substances that can positively affect our brains, stimulate protective cells called astrocytes, and delay neurodegeneration. This may make it interesting to do more research on these effects.
But even today, it is common that among the various recommendations recommended in certain mental disorders are mentions of dietary and dietary aspects such as reducing the consumption of certain substances or monitoring diet specific (eg by increasing the level of tryptophan consumed, which in turn is linked to the secretion of neurotransmitters).
Guyton, AC (2001), Treatise on medical physiology. (10th ed.), Ed. McGraw-Hill Inter-American.
Mirre, JC (2012). The importance of the second brain. Discovery Hi, 147.
Rothhammer, V. et al. (2016). Type I interferons and microbial metabolites of tryptophan modulate astrocyte activity and central nervous system inflammation via the aryl hydrocarbon receptor. Nature Medicine, 22; 586-597.