Saturday, August 13, 2022

Which Part Of The Brain Activates The Stress Response

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Stress Kills Brain Cells

What activates Anxiety Triggers and the Fight or Flight responses in the Brain?

It has been suggested by researchers that chronic stress can even kill new neurons in the brains hippocampus. The hippocampus is one of only two locations where neurons are produced. Despite the fact that the formation of new neurons does not seem to be affected, research shows that new neurons produced during periods of stress are more likely to die within a week.

Major Depression As A Disorder Of Adaptation

As reviewed previously, the stress response system is a stereotyped, adaptive repertoire that ensures survival during threatened homeostasis. Major depression, by definition, is associated with relatively unshifting affect and simultaneous changes in fundamental biological processes that regulate sleep, food intake, metabolism, and reproduction. Similarities between the stress response and the phenomenology of melancholia prompted us to first postulate that the clinical and biochemical manifestations of this disorder reflect a dysregulation in stress system mediators. Changes seen during the stress response are under strict control by counterregulatory mechanisms that serve to limit the response in time and magnitude. Melancholia can be seen as a state of chronically and excessively activated stress response, possibly due to an escape of the usual regulatory influences. In that sense, melancholia would be a disorder of adaptation, more specifically, one in which the stress response required for survival becomes dysregulated and is the very source of the illness. In contrast, many symptoms found in atypical depression can reflect a pathological inactivation of stress system mediators. The remainder of this article reviews the lines of evidence indicating the convergence between a dysregulation of the stress response and the biochemical and neurobiological findings in both subtypes of major depression.

M.A. Brostrom, C.O. Brostrom, in, 2007

Changes The Brains Structure

Your brain is composed of both gray matter and white matter. Gray matter is used for decision-making and problem-solving, while white matter is used to connect regions of the brain and communicate information. It has been noted that during times of chronic stress, the myelin sheaths that make up white matter become overproduced, while less gray matter is produced. When this happens, there can be an imbalance in gray and white matter. In some cases, this results in permanent changes to the brains structure.

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A Stress Effects On Gene Expression In An Ever

Figure 2Gene expression changes in hippocampus in response to stress and glucocorticoid challenge depend on the prior stress history of the subject

Hippocampal microarray data reveals stress-induced gene expression changes. Solid bars represent the number of significantly increased genes and hatched bars represent significantly decreased genes identified by pairwise comparisons of each stress group with age-matched controls.

Proportional Venn diagram illustrating the genes significantly altered by both the acute stress, chronic stress, and CORT injection conditions. The numbers of genes unique to each comparison that were increased or decreased are listed next to arrows indicating the direction of change.

Venn diagram of genes altered by each FST condition reveals a core of 95 genes that were always changed by this stressor. The large number of unique gene expression changes in each condition shows that the response to FST is altered by the stress history of the group, with the vast majority of changes occurring when the animal is exposed to a novel stressor immediately after a chronic stress exposure, as also shown in .

Venn diagram illustrating that the number of genes significantly different from controls after recovery from CRS are mostly unique from those significantly altered by CRS. Reprinted from18 by permission.

What Is Stress And How Does It Affect Our Brains And Bodies

14 Ways to Reduce Anxiety Naturally

Stress is our reaction to a threatening event or stimulus. Such events and stimuli are called stressors. People perceive and react to stressors differently. Something one person would rate as highly stressful might be rated as considerably less stressful by someone else. These responses are affected by such factors as genetics and life experiences.

Stress can be classified as positive, tolerable or toxic. Toxic stress occurs when we are faced with a continuous stressor or triggered by multiple sources and can have a cumulative toll on our physical and mental health. It is an experience that overwhelms us and leaves us feeling powerless and hopeless.

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Calming Your Brain During Conflict

Conflict wreaks havoc on our brains. We are groomed by evolution to protect ourselves whenever we sense a threat. In our modern context, we dont fight like a badger with a coyote, or run away like a rabbit from a fox. But our basic impulse to protect ourselves is automatic and unconscious.

We have two amygdala, one on each side of the brain, behind the eyes and the optical nerves. Dr. Bessel Van Der Kolk, in his book The Body Keeps the Score, calls this the brains smoke detector. Its responsible for detecting fear and preparing our body for an emergency response.

When we perceive a threat, the amygdala sounds an alarm, releasing a cascade of chemicals in the body. Stress hormones like adrenaline and cortisol flood our system, immediately preparing us for fight or flight. When this deeply instinctive function takes over, we call it what Daniel Goleman coined in Emotional Intelligence as amygdala hijack. In common psychological parlance we say, Weve been triggered. We notice immediate changes like an increased heart rate or sweaty palms. Our breathing becomes more shallow and rapid as we take in more oxygen, preparing to bolt if we have to.

Further Reading

    In the throes of amygdala hijack, we cant choose how we want to react because the old protective mechanism in the nervous system does it for us even before we glimpse that there could be a choice. It is ridiculous.

    Practicing Mindfulness in Conflict

    Step 1: Stay present.

    What Happens During The Fight

    In response to acute stress, the body’s sympathetic nervous system is activated by the sudden release of hormones. The sympathetic nervous system then stimulates the adrenal glands, triggering the release of catecholamines .

    This chain of reactions results in an increase in heart rate, blood pressure, and breathing rate. After the threat is gone, it takes between 20 to 60 minutes for the body to return to its pre-arousal levels.

    You can probably think of a time when you experienced the fight-or-flight response. When faced with something frightening, you can feel your heartbeat quicken, you may start breathing faster, and your entire body becomes tense and ready to take action.

    The fight-or-flight response can happen in the face of an imminent physical danger or as a result of a psychological threat .

    Physical signs that can indicate the fight-or-flight response has kicked in include:

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    The Hypothalamicpituitaryadrenal Axis In The Stress Response

    The HPA axis is the most critical component of the stress response system. CRF is released from the paraventricular nucleus of the hypothalamus, causing release of ACTH from the pituitary, which stimulates release of cortisol from the adrenals. This axis is involved in a negative-feedback loop that regulates cortisol release .

    Human Neuroimaging Studies Of The Hippocampus

    PTSD and the Brain

    Complementing animal studies of stress-related processes mediated by and affecting neuroplasticity in the hippocampus, a growing number of human structural neuroimaging studies have begun to examine stress processes in association with aspects of gross hippocampal morphology. For example, individuals with stress-related psychiatric disorders, such as major depressive disorder and post-traumatic stress disorder, show volumetric reductions in the hippocampus.â Reduced hippocampal volume has also been found in Cushing’s Disease. Interestingly, in Cushing’s, surgical correction of hypercortisolemia has been reported to at least partially reverse hippocampal volume reduction as well as mood and memory deficits., In depression, there is evidence of volumetric increase in the hippocampus after antidepressant treatment, suggesting that the deficits in depression are potentially reversible. Moreover, there is increasing support for the notion that targeting the plasticity of the hippocampus in depression and mood disorders may underpin pharmacological and nonpharmacological treatment efficacy.

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    Video: How Stress Affects Your Brain

    When we encounter a stressor, our brain and body respond by triggering a series of chemical reactions that prepare us to engage with or run away from the stressor. Two hormones that we release are adrenaline, which prepares muscles for exertion, and cortisol, which regulates bodily functions. If a stressor is exceptionally frightening, it might cause us to freeze and become incapacitated . The stress response triggered by these two hormones causes our:

    • Blood pressure to rise
    • Digestive system to slow down
    • Blood to clot more quickly

    Thousands of years ago, people who stumbled upon a hungry saber-toothed tiger or other predator would be more likely to survive the encounter if they were able to spring up and sprint away swiftly. An increase in blood pressure and heart rate and a slowdown of digestive processes meant more energy could be directed toward escaping. If they couldnt run quickly enough, their odds of surviving a wound from the hungry tiger were better if their blood clotted rapidly.

    Today, this physical response to stress, if unrelieved, can be damaging to our health. Unrelieved stress is a known risk factor in many of the leading causes of premature death among adults, including conditions and illnesses such as heart disease, hypertension, stroke, type 2 diabetes, and a poorly functioning immune system . Chronic stress is also a potential risk factor for depression, addiction, and suicide .

    The Mind And Mental Health: How Stress Affects The Brain

    Stress continues to be a major American health issue, according to the American Psychological Association. More than one-third of adults report that their stress increased over the past year. Twenty-four percent of adults report experiencing extreme stress, up from 18 percent the year before.

    Its well-known that stress can be a detriment to overall health. But can stress actually change the physiology of the brain? Science says yes.

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    Leading Causes Of Stress

    Stress occurs for a number of reasons. The 2015 Stress in America survey reported that money and work were the top two sources of stress for adults in the United States for the eighth year in a row. Other common contributors included family responsibilities, personal health concerns, health problems affecting the family and the economy.

    The study found that women consistently struggle with more stress than men. Millennials and Generation Xers deal with more stress than baby boomers. And those who face discrimination based on characteristics such as race, disability status or LGBT identification struggle with more stress than their counterparts who do not regularly encounter such societal biases.

    Conflict Of Interest Statement

    Brain in Crisis &  Chronic Stress

    The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


    Hostinar, C. E., Sullivan, R. M., and Gunnar, M. R. 2014. Psychobiological mechanisms underlying the social buffering of the hypothalamicpituitaryadrenocortical axis: a review of animal models and human studies across development. Psychol. Bull. 140:25682. doi:10.1037/a0032671

    Gee, D. G., Gabard-Durnam, L., Telzer, E. H., Humphreys, K. L., Goff, B., Shapiro, M., et al. 2014. Maternal buffering of human amygdala-prefrontal circuitry during childhood but not during adolescence. Psychol. Sci. 25:206778. doi:10.1177/0956797614550878

    Guassi Moreira, J. F., and Telzer, E. H. 2016. Mother still knows best: maternal influence uniquely modulated adolescent reward sensitivity during risk taking. Dev. Sci. 111. doi:10.1111/desc.12484

    Gee, D. G., Gabard-Durnam, L. J., Flannery, J., Goff, B., Humphreys, K. L., Telzer, E. H., et al. 2013. Early developmental emergence of human amygdalaprefrontal connectivity after maternal deprivation. Proc. Natl. Acad. Sci. U.S.A. 110:1563843. doi:10.1073/pnas.1307893110

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    D Being Stressed Out: Example Of Sleep Deprivation And Its Consequences

    The common experience of being stressed out has as its core the elevation of some of the key systems that lead to allostatic overload: cortisol, sympathetic activity, and proinflammatory cytokines, with a decline in parasympathetic activity. Nowhere is this better illustrated than for poor or inadequate sleep, which is a frequent result of being stressed out. Sleep deprivation produces an allostatic overload that can have deleterious consequences.

    Because the brain is the master regulator of the neuroendocrine, autonomic, and immune systems, as well as behavior , alterations in brain function by chronic stress can, therefore, have direct and indirect effects on the cumulative allostatic overload. Reduced sleep duration has been reported to be associated with increased body mass and obesity in the NHANES study . Sleep restriction to 4 h of sleep per night increases blood pressure, decreases parasympathetic tone, increases evening cortisol and insulin levels, and promotes increased appetite, possibly through the elevation of ghrelin, a proappetitive hormone, along with decreased levels of leptin . Moreover, proinflammatory cytokine levels are increased with sleep deprivation, along with decreased performance in tests of psychomotor vigilance, and this has been reported to result from a modest sleep restriction to 6 h/night .

    How To Control The Fight Or Flight Response

    Often times stressors that arent life threating dont havea clear on or off switch, says Dr. Fisher. Thats where we see some of thedetrimental effects of prolonged stress because its not going away. Its achronic stress to our immune system.

    Work, bills, kids, your marriage, finances and health are some of the biggest non-life threatening stressors. How you interpret these things can affect your bodys reaction and can contribute to anxiety disorders.

    Some people are having the fight or flight response whenthey go to work or see that their kid didnt clean up their room, says Dr.Fisher. It can vary from person to person in terms of the situations that cantrigger the stress response, but were finding that certain conditions orhealth states can be associated with this imbalance.

    Some people who get in a car accident are too afraid to drive again or cant drive past the spot where the accident was because of fear and anxiety. It becomes a generalized fear response to a situation that isnt particularly dangerous anymore. This can also happen with work or strained relationships. The next thing you know, your fight or flight response is falsely activated, putting you in a state of chronic stress.

    Dr. Fisher says stress management is critical to overallhealth. Its important to think big picture when you feel yourself starting toget worked up over something that you know is not a true threat or danger.

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    More Susceptible To Mental Illness

    An imbalance between white and gray matter can also play a role in the development of mental illness. The theory is that having excess myelin in certain areas of the brain interferes with the timing and balance of communication. It was also noted that chronic stress can negatively alter hippocampal function. The hippocampus is involved in memory, specifically spatial memory, memory consolidation, and memory transfer.

    Your Brain On Stress: Understanding The Stress Response

    How Stress Affects Your Brain | Neuro Champions

    You know that feeling: the hands get clammy and your cheeks are flushed. Your jaw starts to clench and your body tightens. Its time for fight or flight.

    Any stressful situation, brought on either by external circumstances or internal struggles, can be hard to grapple with at times. Even the word stress can bring about stress within the body.

    Stress, particularly chronic or stress related to an overwhelming sense of trauma, has a profound effect on us. Stress decreases working memory which makes you more prone to poor management decisions and errors. Stress also reduces your lymphocytes which can make you more susceptible to physical illness. It also ages you prematurely. Its ugly!

    The way to find relief from stress and anxiety starts with understanding the stress response process. And that starts with knowing your brain.

    What stress is and isnt

    What is stress, exactly? The phrase stress was first used by endocrinologist Hans Selye in 1936, who defined it as the non-specific response of the body to any demand for change.

    Sensing a need to react, the body will kick into action. The nervous system will shift from a parasympathetic to a sympathetic state, heightening awareness. The adrenal glands release adrenaline throughout the body, priming it for rapid response. If the demand continues, cortisol keeps the body in high alert.

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    How And Where Does Anxiety Start In The Brain

    When we get scared or anxious, the startle response is picked up by the amygdala in the brain. This is when we begin to sweat, our heart races, energy surges, blood pressure increases. This all occurs even before we are actually aware of the threat! We will cover more of this in our next post.

    The amygdala then sends information to the thalamus. This area of the brain takes in all sensory information and sends messages to the appropriate areas of the brain including the cortex.

    Once the messages about the threat reaches the cortex, it is the cortex that decides if the threat is actually dangerous or not. If so, the response of the amygdala is reinforced and the fight or flight response continues!

    Lets take a look at the function of brain structures that may play a role in allowing anxiety to increase.

    Human Neuroimaging Studies Of The Amygdala

    Complimenting the above animal work, the amygdala has been shown to be central to emotion and stress-related processes humans.â Specifically, there is human functional neuroimaging evidence that the amygdala is involved in mediating forms of peripheral stress reactivity that have been linked to physical health outcomes. For example, individual differences in amygdala reactivity to emotionally salient stimuli have been shown to covary with physiological parameters associated with cardiovascular disease risk, including basal levels of autonomic-cardiac control, stressor-evoked changes in blood pressure, and diurnal variations in the secretion of the stress hormone, cortisol. Most recently, it has been demonstrated that individuals who express greater amygdala reactivity to threatening social cues also exhibit higher levels of preclinical atherosclerosis, as determined noninvasively by a thickening of the intima-media layers of carotid artery vessel wall complex. Moreover, in that study, individuals who showed lower levels of preclinical atherosclerosis exhibited a pattern of functional connectivity between the amygdala and ACC that suggested a potentially greater down-regulation of the amygdala by this area of the prefrontal cortex during the processing of threatening social cues.

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