Our evolution has developed two systems in order to adapt to environmental requirements:

  • the so-called stress axis, which works on humoral (by the secretion of hormones) pathways.

  • the autonomic nervous system divided into sympathetic and parasympathetic nervous system, which is controlled neuronally (electrically via nerve impulses) and is first activated when required.

Stress Axis

Is a hormone-controlled complex activation system starting in the brain stem (hypothalamus) via the pituitary gland (hypophysis) to the adrenal cortex, which secretes the hormone cortisol. When overstimulated, there is a constantly increased secretion with negative effects up to damage in brain structures with the corresponding increasing restrictions of brain functions (diminished attention and concentration, decrease of the executive functions and response inhibition, ie of the general cerebral control capacity, limitation of memory functions visually and verbally) which chronize with time. This can lead to irreversible cognitive deficits. Cortisol leads to an objective reduction of the cerebral gray matter (ie the brain cells). The neurogenesis (the regeneration and the growth of nerve cells) is inhibited.

Autonomic Nervous System

The autonomous nervous system is located in different brain regions. The connection to the body takes place through two often complementary active systems. The sympathetic nervous system, responsible for activation and the parasympathetic nervous system responsible for homeostasis and regenerative processes. The vagus nerve, which is associated with the parasympathetic nervous system, plays a dominant role. Dysfunctions here can lead to serious physical disorders, eg. high catecholamine values (adrenaline released by the sympathetic nervous system) can lead to necrosis (cell death) in the heart muscle. The risk of heart disease is thus increased 3-4 times.

The following table illustrates examples of opposing mechanisms of action existing between the two systems, which often act in a complementary manner and thus lead integrally to the respective required state:

PARASYMPATHETIC NERVOUS SYSTEMSYMPATHETIC NERVOUS SYSTEM
IntroductionIts general function is to control homeostasis and the body's rest-and-digest response.Its general action is to mobilize the body's fight-or-flight response.
FunctionControls the body's restorative processes while at rest.Controls the body's response during perceived threat.
LocalisationVagus nerve, sacral spineSpinal cord, thoracic and lumbar spinal cord
Activates response ofRest and digestFight-or-flight
Neuronal PathwaysLonger pathways, faster systemShort neurons, slightly slower system
General Body ResponseDownregulation and counterbalance; restores body to state of calm.Body speeds up, tenses up, becomes more alert. Functions not critical to survival shut down.
Cardiovascular System (heart rate)Decreases heart rateIncreases contraction, heart rate
Pulmonary System (lungs)Bronchial tubes constrictBronchial tubes dilate
Musculoskeletal SystemMuscles relaxMuscles contract
PupilsConstrictDilate
Gastrointestinal SystemIncreases stomach movement and secretionsDecreases stomach movement and secretions
Salivary GlandsSaliva production increasesSaliva production decreases
Adrenal CortexNo involvementReleases adrenaline
Glycogen to Glucose ConversionNo involvementIncreases; converts glycogen to glucose for muscle energy
Urinary ResponseIncrease in urinary outputDecrease in urinary output

source: diffen.com