The Impact of Yoga on the Nervous System
Yoga works on the whole body and mind. And especially on the autonomic nervous system providing many benefits. This is one of the reasons for the worldwide success of this practice.
First of all you have to understand how our nervous system works.
We have a central nervous system (CNS) and a peripheral nervous system (PNS):
CNS is made up of the brain, cerebellum, brainstem, spinal cord.
PNS is a set of nerves connecting the different parts of the body to the central nervous system (cranial nerves, spinal nerves - thoracic, lumbar, sacral).
The peripheral nervous system includes
- Somatic nervous system corresponding to the transmission of information from the skin to the spinal cord independently of our will.
- Autonomous nervous system (neuro-vegetative nervous system) regulating automatic bodily processes such as heart rate, blood circulation, respiratory rate, blood pressure, digestion, temperature regulation. It acts on the internal organs independently of our will. There are two: sympathetic and parasympathetic system.
Yoga has a direct action on the sympathetic and para-sympathetic system.
Sympathetic nervous system: This is the protective nervous system that goes into place in the face of danger. It is called "fight or flight (& freeze)". It is the setting in motion and consumption of energy to ensure the defense of the body. This is the state of alert, of vigilance. Fight or flight: The brain produces adrenaline and corticosteroids, the muscles contract to be ready to flee, the pupils dilate to better perceive the danger, the heart rate increases to improve blood flow and oxygenation of muscle cells, breathing fastens and becomes shallow, the body begins to sweat to evacuate excess heat, the mouth becomes dry and digestion stops to use energy for survival and not “waste” it to digest. You really have to imagine the gazelle being chased by a tiger to understand the effects on the body. It is our radar that detects danger and prepares the body for survival. It is therefore good and essential.
Parasympathetic nervous system: This is the nervous system that contributes to a relaxed state of the body. It is called “rest & digest.” It is the storage of energy: The system produces acetylcholine, a neurotransmitter that regulates the basic functions of the body: digestion, breathing, healing, sleep, dream cycles. Breathing & heart rate slow down; digestion begins with the release of insulin, increased salivary, gastric and intestinal secretions; sleep is deep and restorative; the pupils retract (since there is no danger); the body cooled; it stimulates the sexual appetite. This system allows us to recover from danger or prepare the body for danger by putting energy (through digestion) in reserve. It is also good and essential for the proper functioning of the body.
When these two systems are in balance, we speak of homeostasis, a basic tone. When all is well these two systems work together to provide us with adequate and appropriate reactions with our environment and with ourselves.
The problem begins when one of them is too strongly and too often solicited, or rather when the other is not strong enough to keep up. Then, the nervous response is no longer adapted to the situation. For example, this is the case when our sympathetic nervous response is "on" when there is no danger. It's starting to overheat. At the same time, the parasympathetic system no longer works as it should since it is under less strain. This is called a weak tone of the parasympathetic system which counterbalances the physiological effects of the system. The practice of yoga therefore invigorates these two branches of the neuro-vegetative system and brings them back into balance.