The Effects of Stress On Brain Function

The Effects of Stress On Brain Function

When a situation is perceived as unpleasant or dangerous, a general response to stress is taking place in our body. Depending on the situation and previous experience, the individual will adopt a behavioral response to try control the situation. This is commonly knowns as the fight or flight response.

From the perception of danger to the secretion of hormones the brain prepares the body to deal with it, putting into play: 1) the limbic system, 2) the hypothalamus, 3) the pituitary and 4) the adrenal glands. They secrete glucocorticoids (such as cortisol in humans, for example) which will interact with serotonin receptors of the brain.

When someone experiences a stressful event, blood glucocorticoid levels increase. Stress causes activation of the hypothalamus, which then secretes the hormone CRH (for “corticotropin-releasing hormone”). This hormone in turn, causes the pituitary to produce the hormone ACTH (adrenocorticotropin) which circulates in the bloodstream and reaches the adrenal glands where it causes the release of cortisol.

This process forms a negative feedback loop where the excess active cortisol receptors brain glucocorticoid and suppresses the production of CRH. Depressed patients, however, this loop no longer works where excessive production of CRH and cortisol.

When a situation is perceived as unpleasant or dangerous, a general response to stress is taking place in our body. Depending on the situation and previous experience, the individual will adopt a behavioral response to try control the situation. This is commonly knowns as the fight or flight response.

From the perception of danger to the secretion of hormones the brain prepares the body to deal with it, putting into play: 1) the limbic system, 2) the hypothalamus, 3) the pituitary and 4) the adrenal glands. They secrete glucocorticoids (such as cortisol in humans, for example) which will interact with serotonin receptors of the brain.

When someone experiences a stressful event, blood glucocorticoid levels increase. Stress causes activation of the hypothalamus, which then secretes the hormone CRH (for “corticotropin-releasing hormone”). This hormone in turn, causes the pituitary to produce the hormone ACTH (adrenocorticotropin) which circulates in the bloodstream and reaches the adrenal glands where it causes the release of cortisol.

This process forms a negative feedback loop where the excess active cortisol receptors brain glucocorticoid and suppresses the production of CRH. Depressed patients, however, this loop no longer works where excessive production of CRH and cortisol.

Several seriously depressed patients have high blood levels of cortisol caused by chronic stress.

Chronic stress and / or high levels of glucocorticoids in rats alter some of its serotonin receptors (increased cortical 5-HT2A receptors and reduced 5-HT1A receptors in the hippocampus). These same changes are observed in human victims of suicide or disease causing hypersecretion of glucocorticoids. However, chronic administration of antidepressants cause changes opposed to serotonin to those produced by chronic stress. It also reverses the hypersecretion of stress hormones.

Moreover, several glucocorticoid receptors (GR) and the mineralocorticoid (MR) (see box) are located in the hypothalamus and hippocampus, two structures involved in controlling our mood and ability to experience pleasure. These receptors are sensitive to both the level and the duration of activation of different steroids in the body, activating their dynamic will directly impact the adopted behavioral response.

For example, corticosteroids flowing at a low rate facilitate, via the MR receivers, orientation reactions and temporary paralysis associated with fear. At high flow rates, such as during chronic stress, but rather learning the inefficiency of the action that is potentiated via the GR receptors.

Prolonged chronic stress also seems to alter the response of MR and GR receptor and has very harmful consequences on the mental balance of a person, especially when social or family support is absent. Under these conditions, the adaptive response to the very origin of glucocorticoids becomes downright maladaptive.

It has long been known that people with depression show a hyperactivity of the hypothalamic-pituitary-adrenal axis (HPA).This chronic stress would cause structural changes in certain brain regions. This is the case for example of hippocampal region which suffers significant neuronal loss as a result of prolonged stress.

Other studies have also reported a decrease in the number of glucocorticoid receptors in the hippocampus and prefrontal cortex of suicide victims. Although it is unclear whether these structural changes are genetic where the result of a chronic activation of the HPA axis, it remains consistent with hyperactivity.

Another example: in people with Cushing’s syndrome, a disease in which excess cortisol is produced, there is a high incidence of depression. In addition, depression ceases when their cortisol levels go back to normal levels with the treatments.

Everything leads us to believe that the end product of the HPA axis, glucocorticoids play a role in depression by influencing several neurotransmitter systems including serotonin, norepinephrine and dopamine, all three involved in depression.

A strong, healthy brain is more resistant to the effects of stress and is able to cope far better. Brain supplements like Neurolon help improve the brains stress tolerance levels.

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