The Stress Response

http://en.wikipedia.org/wiki/Stress_(medicine)#Folklore_of_stress

http://en.wikipedia.org/wiki/Fight-or-flight_response#Negative_effects_of_the_stress_response_in_humans

http://en.wikipedia.org/wiki/Acute_stress_reaction

http://en.wikipedia.org/wiki/Defense_physiology

http://en.wikipedia.org/wiki/Hypothalamic-pituitary-adrenal_axis

http://en.wikipedia.org/wiki/Attachment_theory

http://en.wikipedia.org/wiki/Reactive_attachment_disorder

http://en.wikipedia.org/wiki/Emotional_self-regulation

stress : As it pertains to the term defense physiology, the term stress refers to a perceived threat to the continued functioning of the body / life according to its current state.

threat : What constitutes a threat as it pertains to defense physiology? A threat may be consciously recognized or not. A physical event (a loud noise or car collision), a chemical or a biological agent which alters (or has the possibility to alter) body function (physiology) away from optimum or healthy functioning (or away from its current state of functioning) may be perceived as a threat (also called a stressor).

Life circumstances, though posing no immediate physical danger, could be perceived as a threat. Anything that could change the continuing of the person’s life as they are currently experiencing it could be perceived as a threat.

[perceived.

The perception of a threat may also trigger an associated ‘feeling of distress’. Physiological reactions triggered by mind cannot differentiate both the physical or mental threat separately, Hence the “fight-or-flight” response of mind for the both reactions will be same.

[Acute Stress Reaction - The body executes the “Fight-or-flight” reaction to get the body out of danger quickly. When the timing between the threat and the resolution of the threat are close, the “fight-or-flight” reaction is executed, the threat is handled, and the body returns to its previous state (taking care of the business of life – digestion, relaxation, tissue repair etc.). The body is designed to stay in this mode for only a short time.

Chronic Stress State - When the timing between the threat and the resolution of the threat are more distant (the threat or the perception of threat is prolonged or other threats occur before the body has recovered), the “fight-or-flight” reaction continues and becomes the new ‘standard operating condition’ of the body, chronic Defense Physiology. Continuing in this mode produces significant negative effects (distress) in many aspects of body functioning (physical, mental and emotional distress).

 

The fight-or-flight response (also called the fight-or-flight-or-freeze response, hyperarousal, or the acute stress response) was first described by Walter Bradford Cannon.[1][2][3][4][5]

His theory states that animals react to threats with a general discharge of the sympathetic nervous system, priming the animal for fighting or fleeing. This response was later recognized as the first stage of a general adaptation syndrome that regulates stress responses among vertebrates and other organisms.

Physiology

Catecholamine hormones, such as adrenaline or noradrenaline, facilitate immediate physical reactions associated with a preparation for violent muscular action. These include the following:[6]

[zebra. If the zebra sees a lion closing in for the kill, the stress response is activated. The escape requires intense muscular effort, supported by all of the body’s systems. The sympathetic nervous system’s activation provides for these needs. A similar example involving fight is of a cat about to be attacked by a dog. The cat shows accelerated heartbeat, piloerection (hair standing on end, normally for conservation of heat), and pupil dilation, all signs of sympathetic arousal.[6] Note that the zebra still maintains homeostasis in all states.

Though Cannon, who first proposed the idea of fight-or-flight, provided considerable evidence of these responses in various animals, it subsequently became apparent that his theory of response was too simplistic. Animals respond to threats in many complex ways. Rats, for instance, try to escape when threatened, but will fight when cornered. Some animals stand perfectly still so that predators will not see them. Many animals freeze or play dead when touched in the hope that the predator will lose interest.

Others have more exotic self-protection methods. Some species of fish change color swiftly, to camouflage themselves. These responses are triggered by the sympathetic nervous system, but, in order to fit the model of fight or flight, the idea of flight must be broadened to include escaping capture either in a physical way or in a sensory way. Thus, flight can be disappearing to another location or just disappearing in place. And often both fight and flight are combined in a given situation.

The fight or flight actions also have polarity – the individual can either fight or flee against something that is threatening, such as a hungry lion, or fight for or fly towards something that is needed, such as the safety of the shore of a raging river.

A threat from another animal does not always result in immediate fight or flight. There may be a period of heightened awareness, during which each animal interprets behavioral signals from the other. Signs such as paling, piloerection, immobility, sounds, and body language communicate the status and intentions of each animal. There may be a sort of negotiation, after which fight or flight may ensue, but which might also result in playing, mating, or nothing at all. An example of this is kittens playing: each kitten shows the signs of sympathetic arousal, but they never inflict real damage.

[[7]

Males and females tend to deal with stressful situations differently. Males are more likely to respond to an emergency situation with aggression (fight), while females are more likely to flee (flight), turn to others for help, or attempt to defuse the situation – ‘tend and befriend‘. During stressful times, a mother is especially likely to show protective responses toward her offspring and affiliate with others for shared social responses to threat.[4]

[constipation, anorexia, erectile dysfunction, difficulty urinating, and difficulty maintaining sexual arousal. These are functions that are controlled by the parasympathetic nervous system and therefore suppressed by sympathetic arousal.[6]

Prolonged stress responses may result in chronic suppression of the immune system, leaving the body open to infections. However, there is a short boost of the immune system shortly after the fight or flight response has been activated. This may have filled an ancient need to fight the infections in a wound that one may have received during interaction with a predator.

Stress responses are sometimes a result of mental disorders such as post-traumatic stress disorder, in which the individual shows a stress response when remembering a past trauma, and panic disorder, in which the stress response is activated by the catastrophic misinterpretations of bodily sensations.

For potential positive meanings, reference can be made to Hans Selye‘s psychological concept of eustress or good, healthy stress.

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An adrenaline rush is the fight or flight response of the adrenal gland, in which it releases adrenaline (epinephrine). When releasing adrenaline, one’s body releases dopamine which can act as a natural pain killer. An adrenaline rush causes the muscles to perform respiration at an increased rate improving strength. It also works with the nervous system to interpret impulses that trigger selective glands.

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“Acute stress response” was first described by Walter Cannon in the 1920s as a theory that animals react to threats with a general discharge of thesympathetic nervous system. The response was later recognized as the first stage of a general adaptation syndrome that regulates stress responses among vertebrates and other organisms.

The onset of a stress response is associated with specific physiological actions in the sympathetic nervous system, both directly and indirectly through the release of adrenaline and to a lesser extent noradrenaline from the medulla of the adrenal glands. These catecholamine hormones facilitate immediate physical reactions by triggering increases in heart rate and breathing, constricting blood vessels. An abundance of catecholamines at neuroreceptor sites facilitates reliance on spontaneous or intuitive behaviors often related to combat or escape.

Normally, when a person is in a serene, unstimulated state, the “firing” of neurons in the locus ceruleus is minimal. A novel stimulus, once perceived, is relayed from the sensory cortex of the brain through the thalamus to the brain stem. That route of signaling increases the rate of noradrenergic activity in the locus ceruleus, and the person becomes alert and attentive to the environment.

If a stimulus is perceived as a threat, a more intense and prolonged discharge of the locus ceruleus activates the sympathetic division of the autonomic nervous system (Thase & Howland, 1995). The activation of the sympathetic nervous system leads to the release of noradrenaline from nerve endings acting on the heart, blood vessels, respiratory centers, and other sites. The ensuing physiological changes constitute a major part of the acute stress response. The other major player in the acute stress response is the hypothalamic-pituitary-adrenal axis.

 

This natural reaction is known as the stress response. Working properly, the body’s stress response enhances a person’s ability to perform well under pressure. But the stress response can also cause problems when it overreacts or fails to turn off and reset itself properly.

Stress is not directly created by external events, but instead by the internal perceptions that cause an individual to have anxiety/negative emotions surrounding a situation, such as pressure, discomfort, etc., which they then deem “stressful”. Humans experience stress, or perceive things as threatening, when they do not believe that their resources for coping with obstacles (stimuli, people, situations, etc.) are enough for what the circumstances demand. When we think the demands being placed on us exceed our ability to cope, we then perceive stress. The feelings often associated with experiencing stress are anxiety and being overwhelmed.

The stress response is mediated by the activation of two major systems.

In response to a stressor, neurons with cell bodies in the paraventricular nuclei (PVN) of the hypothalamus secrete corticotropin-releasing hormone (CRH) and arginine-vasopressin (AVP) into the hypophyseal portal system.

The locus ceruleus and other noradrenergic cell groups of the adrenal medulla and pons, collectively known as the LC/NE system, also become active and use brain epinephrine to execute autonomic and neuroendocrine responses, serving as a global alarm system.

HPA System

The first one is the hypothalamic-pituitary-adrenal (HPA) system which stimulates the adrenal cortex to release glucocorticoid, cortisol in primates and corticosterone in rodents, into the blood stream.

The HPA axis, a major part of theneuroendocrine system involving the interactions of the hypothalamus, the pituitary gland, and the adrenal glands, is also activated by release of CRH and AVP. This results in release of adrenocorticotropic hormone (ACTH) from the pituitary into the general bloodstream, which results in secretion of cortisol and other glucocorticoids from the adrenal cortex. The related compound cortisone is frequently used as a key anti-inflammatory component in drugs that treat skin rashes and in nasal sprays that treat asthma and sinusitis. Recently, scientists realized the brain also uses cortisol to suppress the immune system and reduce inflammation within the body. These corticoids involve the whole body in the organism’s response to stress and ultimately contribute to the termination of the response via inhibitory feedback.

central nervous system (CNS) hyperarousal

  • ↑ alertness
  • ↑ reactivity
  • ↑ restlessness

Glucocorticoids are required for extinction of predator stress-induced hyperarousal.
The predator stress paradigm allows us to determine whether glucocorticoids mediate the extinction of fear memories:

  • context-dependent (associative)
  • context-independent (non-associative)

Sympathetic-Adrenomedullary System

The other one is the sympathetic-adrenomedullary system which releases adrenaline from the chromaffin cells in adrenal medulla and noradrenaline from the sympathetic nerve endings, and triggers the flight-and-fight responses.

The autonomic nervous system provides the rapid response to stress commonly known as the fight-or-flight response, engaging the sympathetic nervous system and withdrawing the parasympathetic nervous system, thereby enacting cardiovascular, respiratory, gastrointestinal, renal, and endocrine changes.

autonomic nervous system (ANS) hyperarousal

  • ↑ metabolic rates
  • ↑ body temperatures
  • ↑ electrodermal activity
  • ↑ heart rates
  • ↑ sympathetic tone – mediated in part by corticotrophin-releasing hormone (CRH)
  • ↑ cortisol levels
  • ↑ activation of the hypothalamic-pituitary-adrenal (HPA) axis

 

 

How animals respond to the arrival of a stressor.

Stress as a process with emotional, mental, physiological, behavioural aspects.

The stress response is an inbuilt protective mechanism. When working properly, it helps animals stay focused, energetic, and alert.When you perceive a threat, your nervous system responds by releasing a flood of stress hormones, including adrenaline and cortisol. These hormones rouse the body for emergency action.

Your heart pounds faster, muscles tighten, blood pressure rises, breath quickens, and your senses become sharper. These physical changes increase your strength and stamina, speed your reaction time, and enhance your focus – preparing you to either fight or flee from the danger at hand.
Stress is a normal physical response to events that make you feel threatened or upset your balance in some way. When you sense danger – whether it’s real or imagined – the body’s defenses kick into high gear in a rapid, automatic process known as the “fight-or-flight” reaction, or the stress response.
The stress response is the body’s way of protecting you. When working properly, it helps you stay focused, energetic, and alert. In emergency situations, stress can save your life – giving you extra strength to defend yourself, for example, or spurring you to slam on the brakes to avoid an accident.
The stress response also helps you rise to meet challenges. Stress is what keeps you on your toes during a presentation at work, sharpens your concentration when you’re attempting the game-winning free throw, or drives you to study for an exam when you’d rather be watching TV.
But beyond a certain point, stress stops being helpful and starts causing major damage to your health, your mood, your productivity, your relationships, and your quality of life.

Remember what you learned in high school science about the “Fight or Flight Response”. It’s a primitive survival mechanism – when you experience a threat or stressor, your body prepares itself to either fight the threat, or to run away. It pours out stress hormones, mainly adrenaline and cortisol, which cause you to feel keyed up, your heart races, your muscles tense, your palms may sweat, you breathe quickly. You’re hypervigilant, keying in to nonverbal cues in the other person, such as eye contact, facial expression and body posture, or how close you are to the threat. You can’t think straight. Your brain is so focussed on priming your body to fight or flee (engaging the most basic, primitive parts of the brain that the baby uses), that it doesn’t engage any of your higher-order thinking.

In scientific terms, you’re hyperaroused.

The human body responds to stressors by activating the nervous system and specific hormones. The hypothalamus signals the adrenal glands to produce more of the hormones adrenaline and cortisol and release them into the bloodstream. These hormones speed up heart rate, breathing rate, blood pressure, and metabolism. Blood vessels open wider to let more blood flow to large muscle groups, putting our muscles on alert. Pupils dilate to improve vision. The liver releases some of its stored glucose to increase the body’s energy. And sweat is produced to cool the body. All of these physical changes prepare a person to react quickly and effectively to handle the pressure of the moment.

It’s important to learn how to recognize when your stress levels are out of control. The most dangerous thing about stress is how easily it can creep up on you. You get used to it. It starts to feels familiar even normal. You don’t notice how much it’s affecting you, even as it takes a heavy toll.

In terms of measuring the body’s response to stress, psychologists tend to use Han Selye’s general adaptation syndrome. This model is also often referred to as the classic stress response, and it revolves around the concept of homeostasis. This means that the body’s response to stressors seeks to return to its equilibrium, or the normal level of stress resistance. During the alarm phase, the body begins to build up resistance to the stressor beyond normal resistance levels. The body continues building up resistance throughout the stage of resistance, until either the body’s resources are depleted or the stressful stimulus is removed, leading into the exhaustion phase.
This response is designed to help humans in life or death situations, but all types of stressors can trigger this response. A stress response results in elevated physiological arousal, often associated with the release of stress hormones such ascortisol. The physiological arousal in response to stressors is designed to help the body adapt quickly in order to survive and rid itself of the stressful stimuli.
This physiological stress response involves high levels of sympathetic nervous system activation, often referred to as the “fight or flight” response. The response involves pupil dilation, release of endorphins, increased heart and respiration rates, cessation of digestive processes, secretion of adrenaline, arteriole dilation, and constriction of veins. This high level of arousal is often unnecessary to adequately cope with micro-stressors and daily hassles; yet, this is the response pattern seen in humans, which often leads to health issues commonly associated with high levels of stress.

Good – Bad
The stress response (also called the fight or flight response) is critical during emergency situations, such as when a driver has to slam on the brakes to avoid an accident. It can also be activated in a milder form at a time when the pressure’s on but there’s no actual danger — like stepping up to take the foul shot that could win the game, getting ready to go to a big dance, or sitting down for a final exam. A little of this stress can help keep you on your toes, ready to rise to a challenge. And the nervous system quickly returns to its normal state, standing by to respond again when needed.
But stress doesn’t always happen in response to things that are immediate or that are over quickly. Ongoing or long-term events, like coping with a divorce or moving to a new neighborhood or school, can cause stress, too.
Long-term stressful situations can produce a lasting, low-level stress that’s hard on people. The nervous system senses continued pressure and may remain slightly activated and continue to pump out extra stress hormones over an extended period. This can wear out the body’s reserves, leave a person feeling depleted or overwhelmed, weaken the body’s immune system, and cause other problems.
Although just enough stress can be a good thing, stress overload is a different story — too much stress isn’t good for anyone. For example, feeling a little stress about a test that’s coming up can motivate you to study hard. But stressing out too much over the test can make it hard to concentrate on the material you need to learn.

 

Adaptive – Maladaptive
The stress responses pe ser are not harmful or pathological. In fact a brief stress exposure can induce rapid adaptive physiological responses that enable an organism to react efficiently to the changing environment and therefore are beneficial for survival. For instance, recently it was reported that mice trained
under more stressful conditions showed better learning and memory which was accompanied by enhanced synaptic expression of GluA2 AMPA receptors (Conboy and Sandi, 2010).

Responses to stress include adaptation, psychological coping - see stress management

However, when stress becomes repetitive and uncontrollable, a cascade of neuroplastic processes is initiated and eventually leads to marked morphological and functional alterations in the brain that resemble the pathophysiology observed in patients with stress related depressive disorders (reviewed in Joëls et al., 2007).

Acute – Chronic

Chronic stress – when the body is in a state of stress it releases high levels of norepinephrine and uses up all its dopamine, serotonin, GABA and endorphins coping with the stress.

Chronic Stress
Chronic stress is defined as a “state of prolonged tension from internal or external stressors, which may cause various physical manifestations–eg, asthma, back pain, arrhythmias, fatigue, headaches, HTN, irritable bowel syndrome, ulcers, and suppress the immune system”. Chronic stress takes a more significant toll on your body than acute stress does. It can raise blood pressure, increase the risk of heart attack and stroke, increase vulnerability to anxiety and depression, contribute to infertility, and hasten the aging process. For example, results of one study demonstrated that individuals who reported relationship conflict lasting one month or longer have a greater risk of developing illness and show slower wound healing. Similarly, the effects that acute stressors have on the immune system may be increased when there is perceived stress and/or anxiety due to other events. For example, students who are taking exams show weaker immune responses if they also report stress due to daily hassles. [14]

However, stress that continues over an extended period, even at low levels, can be detrimental to an animal’s health. Many animal diseases and behaviour problems are now understood to be stress-related. Long-term stress means an animal may never get the chance to fully relax. The ability to relax is essential for animal wellbeing, as relaxation allows for optimal healing, and a return to normal, balanced functioning.

Acute Stress Response

  • Stressors perceived as threatening trigger the nervous system to produce hormones to that facilitate quick effective reaction to the perceived danger.
  • Cortisol
  • Adrenal glands produce more adrenaline and cortisol, releasing them into the bloodstream. This speeds up heart and breathing rates, and increases blood pressure and metabolism.
  • more commonly known as the “fight or flight response”
  • When an animal perceives a threat, their nervous system responds by releasing a flood of stress hormones, including adrenaline and cortisol. These hormones rouse the body for emergency action. The stress response is an inbuilt protective mechanism. When working properly, it helps animals stay focused, energetic, and alert.

Chronic Stress Response

  • if even low levels of stress go on too long, it can be detrimental to health.
  • nervous system remains slightly activated and continues to produce stress hormones over an extended period, leaving the animal feeling depleted or overwhelmed, and weakening the immune system.

Eustress – Distress

Selye published in 1975 a model dividing stress into eustress and distress.[3] Where stress enhances function (physical or mental, such as through strength training or challenging work), it may be considered eustress. Persistent stress that is not resolved through coping or adaptation, deemed distress, may lead to anxiety or withdrawal (depression) behavior.
The difference between experiences that result in eustress and those that result in distress is determined by the disparity between an experience (real or imagined) and personal expectations, and resources to cope with the stress. Alarming experiences, either real or imagined, can trigger a stress response.

Cognitive Appraisal Model
Lazarus argued that, in order for a psychosocial situation to be stressful, it must be appraised as such. He argued that cognitive processes of appraisal are central in determining whether a situation is potentially threatening, constitutes a harm/loss or a challenge, or is benign.
Both personal and environmental factors influence this primary appraisal, which then triggers the selection of coping processes. Problem-focused coping is directed at managing the problem, whereas emotion-focused coping processes are directed at managing the negative emotions. Secondary appraisal refers to the evaluation of the resources available to cope with the problem, and may alter the primary appraisal.
In other words, primary appraisal includes the perception of how stressful the problem is and the secondary appraisal of estimating whether one has more than or less than adequate resources to deal with the problem that affects the overall appraisal of stressfulness. Further, coping is flexible in that, in general, the individual examines the effectiveness of the coping on the situation; if it is not having the desired effect, s/he will, in general, try different strategies.

 

Brain scans were one of the many tools used in conducting research on the topic of stress and families, and the scans proved that there is a chemical imbalance that happens in the brain when under stress which causes certain emotional reactions. Thoughts, feelings and behavior are produced through a series of chemical reactions in the brain, and when a particular chemical is not present or is insufficient, the result is seen through unusual behaviors or emotions. In the research done by the University, the chemicals that were most effected by genetics, trauma and prolonged stress were dopamine, Gamma Amino Butyric Acid (GABA), Serotonin and Encephalin.

According toBaylorUniversity, family members in families that undergo significant amounts of stress for long periods of time have short tempers, short attention spans, poor immune systems, and increased emotional burdens.

The Immune System and the Brain

When you have an infection or something else that causes inflammation such as a burn or injury, many different kinds of cells from the immune system stream to the site. Dr. Sternberg likens them to soldiers moving into battle, each kind with its own specialized function. Some are like garbage collectors, ingesting invaders. Some make antibodies, the “bullets” to fight the infectious agents; others kill invaders directly. All these types of immune cells must coordinate their actions, and the way they do that is by sending each other signals in the form of molecules that they make in factories inside the cell.

“It turns out that these molecules have many more effects than just being the walkie-talkie communicators between different kinds of immune cells,” Dr. Sternberg says. “They can also go through the bloodstream to signal the brain or activate nerves nearby that signal the brain.”

These immune molecules, Dr. Sternberg explains, cause the brain to change its functions. “They can induce a whole set of behaviors that we call sickness behavior. . . . You lose the desire or the ability to move, you lose your appetite, you lose interest in sex.” Scientists can only speculate about the purpose of these sickness behaviors, but Dr. Sternberg suggests that they might help us conserve energy when we’re sick so we can better use our energy to fight disease.

These signaling molecules from the immune system can also activate the part of the brain that controls the stress response, the hypothalamus. Through a cascade of hormones released from the pituitary and adrenal glands, the hypothalamus causes blood levels of the hormone cortisol to rise. Cortisol is the major steroid hormone produced by our bodies to help us get through stressful situations. The related compound known as cortisone is widely used as an anti-inflammatory drug in creams to treat rashes and in nasal sprays to treat sinusitis and asthma. But it wasn’t until very recently that scientists realized the brain also uses cortisol to suppress the immune system and tone down inflammation within the body.

  • increase in blood pressure
  • dilation of pupils
  • dry mouth
  • tensing of muscles
  • difficulty concentrating

cause an animal to to increase the animal’s heart and breathing rates. All of this enables an animal to move quickly in a dangerous situation.

  • adrenalin
  • activation of the HPA axis → cortisol