How does stress affect the brain?

We have all read or heard about stress, a natural response that if given in excess can affect our health, however, Do we know what happens in our brain when we are under stress?

The WHO defines stress as "the set of physiological reactions that prepares the body for action." Acute stress that is resolved in the short term can be positive, as it prepares the brain for better performance. However, constant tension can be fatal. This negative impact of stress occurs when it becomes chronic.

• Related article: "Types of stress and their triggers"

Stress hormones

Cortisol is the main stress hormone. When we are in a stressful situation, a signal is sent to the pituitary gland that hormonally activates the adrenal glands (small glands located in the upper part of each kidney). These are the ones that release cortisol, which by rising in the blood increase glucose levels for the whole organism, thus the organs work more efficiently, being appropriate for short times, but in no case for long. In addition, there are the following.

• Glucagon (in a stressful situation, the pancreas releases large doses of glucagon into the bloodstream).
• Prolactin.
• Sex hormones (such as testosterone and estrogens).
• The progesterone whose production decreases in stressful situations.

Changes that stress causes in brain structures

Suffering from chronic stress can cause various reactions in the following areas of our brain:

1. Hippocampus

One of them is the death of neurons in the hippocampus (neurotoxicity). The hippocampus located in the medial part of the temporal lobe of the brain is a structure linked to memory and learning, it belongs on the one hand to the limbic system and on the other to the archicortex, composing together with the subiculum and the dentate gyrus the so-called formation hippocampus. Contains high levels of mineralocorticoid receptors which makes it more vulnerable to long-term biological stress than other brain areas.

Stress-related steroids reduce the activity of some neurons in the hippocampus, inhibit the genesis of new neurons in the dentate gyrus and produce atrophy of the dendrites of the pyramidal cells of the region CEA3. There is evidence of cases in which PTSD may contribute to hippocampal atrophy. In principle, some effects may be reversible if stress is interrupted, although there are studies with rats subjected to stress shortly after birth whose damage to hippocampal function persists throughout the lifetime.

• You may be interested: "Hippocampus: functions and structure of the memory organ"

2. Amygdala

The amygdala is part of the limbic system and is responsible for the processing and storage of emotional reactions. Recent research suggests that when a person is under stress, this region of the brain sends signals to the spinal cord indicating that it should increase the production of white blood cells.

The problem is that an excess of white blood cells can cause arterial inflammation, which can provoke the development of cardiovascular diseases such as strokes, angina pectoris and seizures cardiac.

• You may be interested: "Brain amygdala: structure and functions"

3. Gray and white matter

Another long-term effect of stress is the imbalance between gray matter and white matter in the brain.

Gray matter is mainly made up of cells (neurons that store and process information, and supporting cells called glia) while the white matter is made up of axons, which create a network of fibers that interconnect the neurons. The white matter gets its name from the white sheath, myelin fat surrounding the axons and accelerates the flow of electrical signals from one cell to another.

Chronic stress was found to generate more myelin-producing cells and fewer neurons than normal. Which produces an excess of myelin and, therefore, white matter in some areas of the brain, which modifies balance and internal communication within the brain.

• Related article: "Gray matter of the brain: structure and functions"

Mental diseases

Each person is unique and there are individual differences in the biological mechanisms of stress, they can have a biological basis or be acquired throughout life. They can determine differences in vulnerability or predisposition to develop stress-related disorders.

In short, stress plays an important role in the triggering and evolution of mental disorders, as in post-traumatic stress disorder, anxiety and depression disorders, schizophrenic psychoses and other It is also a risk factor and a significant component in substance abuse and dependence disorders.