How does stress affect the nervous system?

Stress is an emotion that appears when we find ourselves in a situation in which we perceive that our life or well-being is threatened. This emotion implies the activation of several organic mechanisms that are oriented towards having enough energy to be able to face the perceived threat.

As an emotion that it is, it has a neurological substrate, it affects our nervous system. Depending on whether it is a punctual or chronic stress, it will affect our body in one way or another.

Next we will discover what changes occur in our nervous system when we are stressed.

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What effects does stress have on the nervous system?

Stress is an emotion that arises when some change or unforeseen event is perceived in the environment. The function of such emotion is to prepare our body to give a satisfactory response to such changes, arising when the individual feels that the situation overwhelms the resources of which he believes provide.

Definitely, stress helps us to gather all the necessary forces to emerge victorious from the emotionally tense situation.

This mechanism implies a physiological response, activating a series of processes at the organic level to be able to face whatever is necessary. When we are stressed our cardiovascular, metabolic, immune and neuroendocrine systems undergo several changes, all of them to obtain enough energy in the form of glucose for the muscles to perform a fight or flight behavior and overcome the situation.

Next we will see in detail what are the changes that occur in different components of the nervous system when a stress response occurs.

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The autonomic nervous system

The autonomic nervous system acquires a very important role in situations that cause us stress. When we perceive a threat, half of this system is activated and the other is inhibited. These systems are the sympathetic and the parasympathetic.

sympathetic nervous system

The part of the autonomic nervous system that is activated is the sympathetic. Although its origin is in the brain, its projections radiate from the spinal cord contacting all the organs, blood vessels and sweat glands of the body. This component of the nervous system is activated when the brain considers that it is in an emergency situation.

When this system is activated, the hypothalamus gives the order to increase the activity of the adrenal glands. This is a rapid activation of what is known as the sympathetic-adrenomedullary axis (SAM), releasing adrenaline and noradrenaline, two fundamental neurotransmitters in the stress response.

parasympathetic nervous system

The other half of the nervous system, the one that is inhibited, is the parasympathetic, which behaves in this way to not hinder the work of the sympathetic system and facilitate the activation of the structures necessary to be able to give an adequate response to what has activated the response stressful on the body.

Effects of stress on the brain

Stress increases the activity of various structures in the brain to prepare it for future demands. This is the hypothalamus-pituitary-adrenal axis or HPA, which allows resolving short-term stress situations in the face of threats in the following way.

First, the hypothalamus releases a special hormone, corticotropin (CRH). This hormone stimulates the pituitary gland so that it, in turn, releases another substance: adrenocorticotropin (ACTH). This action causes the adrenal glands to secrete three other hormones: adrenaline, noradrenaline and cortisol.

Epinephrine and norepinephrine are catecholamines and they increase blood pressure and heart rate. It is also what means that when we are nervous and stressed, the blood supply is diverted from the gastrointestinal system to the muscles, paralyzing digestion and focusing all the forces and energies to be able to react physically in case of being necessary.

Cortisol causes glucose to be released, action necessary for the body to have enough energy to be prepared for the demands of the situation. In addition, in case of wounds or injuries, cortisol serves to prevent inflammation. The muscles receive blood and sugar to increase strength, the brain increases its concentration so that the body and mind can work together to survive.

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Effects of chronic stress on the nervous system

Stress triggers the levels of glucocorticoids in the bloodstream, so chronic stress can have harmful effects on the body, especially neurons and their ramifications being sensitive. There are structural and functional changes caused by chronic stress in the brain, which as As a consequence, they induce mood disorders and behavioral changes and physiological.

Chronic stress inhibits glucose uptake by neurons, which alters its development and growth. Additionally, too much stress triggers a biochemical cascade in the form of more neural synapses, especially in the hippocampus and prefrontal cortex.

This causes overactivation in these areas, damaging neurons and causing the degradation of their cytoskeleton. Also there is malformation of neuronal proteins and generation of oxygen radicals, which cause neuronal death.

The hippocampus, the amygdala and the prefrontal cortex are structures that are very susceptible to changes, and stress is one of those factors that contributes to their remodeling. The degree of reversibility of such alterations will depend on the duration and potency of the stressors and the amount of neurochemical substances that the stressful episode has released. This brings with it not only effects at the cognitive level, but also involves changes in emotionality, behavior and neuroendocrine functions of the individual.

Effects on the hippocampus

As we have said in the previous section, one of the brain structures most sensitive to changes is the hippocampus. This structure has a high concentration of glucocorticoid receptors and, as a key structure in learning, it is very susceptible to changes due to its cerebral plasticity, which is necessary to house new knowledge. The hippocampus is involved in the creation of new memories by strengthening neural connections. It does not store memories, but it fosters networks that allow previous experiences to be associated.

In the short term, stress causes more oxygen and glucose to reach the brain, which is positive because it increases the activity of this structure and enhances the memory of the stressful situation. This has the advantage that, if what caused us stress happens again, we quickly remember how we handled the situation and thus emerge victorious more quickly.

But, if the stress becomes chronic, glucose and oxygen levels decrease and neurons in the hippocampus begin to atrophy, damaging the connections between them and causing memory problems. This also induces neuronal death.

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Effects on the prefrontal cortex

In people exposed to constant stress, the prefrontal cortex is generally reduced in size, a consequence of structural and functional changes in their neurons associated with prolonged exposure to glucocorticoids.

Silk an overall decline in executive functions, with worse decision-making, low emotional self-regulation and loss of attention, all of which affect the individual's coping abilities. Also affected is the work memory.

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Effects on the cerebral amygdala

Stress increases neural activity in the amygdala and connections to other brain regions. This makes people under chronic stress more aggressivewith fear and anxiety. This makes them more susceptible to behavioral and emotional disturbances, with psychopathology such as depression.