How does stress affect the brain?
We have all read or heard of stress, a natural response that if taken too much can affect our health, however, Do we know what happens in our brain when we suffer stress?
WHO defines stress as "the set of physiological reactions that prepare the body for action". An acute stress that resolves in the short term can be positive, because it prepares the brain for a better performance. However, a constant tension can be fatal. This negative impact of stress occurs when it becomes chronic.
- Related article: "Types of stress and its triggers"
Stress hormones
Cortisol is the main stress hormone. When we are facing a stressful situation, a signal is sent to the pituitary gland that activates the adrenal glands by hormones (small glands located in the upper part of each kidney). These are the ones that release cortisol , that when rising in blood they increase the levels of glucose for the whole organism, thus the organs work with greater efficiency, being appropriate for short times, but in no case for the long ones. In addition, there are the following.
- Glucagon (in a stress situation, the pancreas releases large doses of glucagon into the bloodstream).
- Prolactin .
- Sex hormones (such as testosterone and estrogen)
- Progesterone whose production decreases in stressful situations.
Changes that cause stress in brain structures
Having chronic stress can cause several 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 architvery, composing together with the subiculum and the dentate gyrus the so-called hippocampal formation. Contains high levels of mineralocorticoid receptors which makes it more vulnerable to biological stress in the long term than other brain areas.
Stress-related steroids reduce the activity of some hippocampal neurons, inhibit the genesis of new neurons in the dentate gyrus and produce atrophy of the dendrites of the pyramidal cells of the CEA3 region. There is evidence of cases in which post-traumatic stress disorders can contribute to atrophy of the hippocampus . In principle, some effects may be reversible if stress is interrupted, although there are studies with rats under stress shortly after birth whose damage to hippocampal function persists throughout life.
- Maybe you're interested: "Hippocampus: functions and structure of the organ of memory"
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 suffers from stress, this region of the brain sends signals to the marrow indicating that white blood cell production should increase.
The problem is that an excess of white blood cells can cause arterial inflammation, which can lead to the development of cardiovascular diseases such as strokes, angina and heart attacks.
- Maybe you're interested: "Brain amygdala: structure and functions"
3. Gray and white matter
Another effect of long-term stress is the imbalance between the gray matter and the white matter of the brain.
Gray matter is composed mainly of cells (neurons that store and process information, and support cells called glia) while white matter is made up of axons, which create a network of fibers that interconnect neurons. 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.
It was discovered that chronic stress generated more myelin-producing cells and fewer neurons than normal. Which produces an excess of myelin and, therefore, of white matter in some areas of the brain, which modifies the 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, may have a biological basis or be acquired throughout life. They can determine differences in vulnerability or predisposition to develop disorders related to stress .
In short, stress plays an important role in the unleashing and evolution of mental disorders, such as post-traumatic stress disorders, anxiety and depression disorders, schizophrenic psychoses and others. It also constitutes a risk factor and a significant component in substance abuse and dependence disorders.
