Stress response

Stress reaction is the physical and mental reaction to the effects of stressors which violate the inner balance ( homeostasis ). A distinction must be made between reactions to acute and long-term exposure. Associated terms are “ hyperarousal ” and “acute stress reaction”.

The stress reaction is a very rapid adaptation possibility of the body to emerging dangerous situations, with the aim of ensuring survival, formed by evolution. Energy is provided to enable a reaction that is appropriate to the situation: attack, flight or paralysis, which have proven to ensure survival in the course of evolution. As a further effect, attention is focused on the dangerous situation and other energy-consuming body processes are suppressed, as they are unnecessary or hindering in the acute situation.

The first scientific research into the stress response is the " fight-or-flight " response described by Walter Cannon in 1915 .

The physician Hans Selye conceived the " General Adaptation Syndrome " (1936) as a model of the human reaction to chronic stress .

Fleeing or fighting makes little evolutionary sense for pregnant women and mothers of young children, and Cannon had mainly used male rats for his research. Shelley Taylor and colleagues (2000) found the “ tend and befriend reaction”, which consists of caring for the offspring (tend = to take care of) and the creation of a social network (befriend = to make friends), as a further possible reaction to chronic stress . It is a little more common in women than in men.

According to recent research results, one cannot speak of a uniform stress reaction, since the type and mechanisms of the reaction to psychological stress differ depending on the type of stressor and the emotion triggered by it . In particular, one study showed that surprise and shock were associated with an increased release of the stress hormone cortisol and, at the same time, a reduced prolactin level, whereas anger and humiliation were associated with an increased release of prolactin and reduced cortisol. An increase in the prolactin level tends to be associated with passive coping , a decrease with active coping.

A person's ability to withstand various stressors is called resilience .

physiology

Increased muscle performance

For this purpose, the skeletal muscles are increasingly supplied with oxygen and nutrients that are required for the provision of energy in the form of ATP through the oxidation of glucose and fat .

The blood flow to the muscles is increased by increasing the blood pressure , the circulation speed of the blood and by expanding the blood vessels of the muscles.

The increase in blood pressure is achieved by increasing the heart rate and the stroke volume of the heart and by narrowing the blood vessels near the heart .

The increased need for oxygen is met by increasing breathing ( lung ventilation ) and flushing out red blood cells from the blood-forming tissues.

The increased need for nutrients is covered by the release of fatty acids from the adipose tissue and glucose from the glycogen stores of the muscles and the liver .

Inhibition of the organs of rest

The intestinal muscles are relaxed and digestion is inhibited. Lymphatic organs such as the thymus , spleen and lymph nodes reduce the production of antibodies . Inflammation in the tissues is inhibited.

More reactions

• The general increase in the basal metabolic rate leads to an increase in the core body temperature. This makes the necessary chemical reactions run faster. On the other hand, overheating must be counteracted through increased production of sweat .
• Expansion of the pupils (=> expansion of the field of vision by 10%)
• The kidney holds back water
• The contraction of the hair follicle muscles leads to the straightening of the hair ("goose bumps")

Controlling the stress response

Via the sympathetic nervous system : Information about stressors reaches the cerebrum and the limbic system via the sensory organs . Here the assessment of the situation as a stressful situation takes place. Signals to the hypothalamus trigger nerve impulses to the sympathetic nervous system.

The activity of the sympathetic system changes the activity of the organs:

a) organs of activity

• the pupils dilate;
• the salivary glands produce less and more viscous mucus ;
• the bronchi are dilated;
• the heart rate increases;
• the liver increasingly breaks down glycogen to glucose;

b) Ruhorgane

• the stomach movement is reduced;
• the sexual organs are inhibited.

At the same time, the sympathetic nervous system activates the adrenal medulla , which releases adrenaline ( SNN axis ).

With the help of adrenaline and noradrenaline : The adrenaline and noradrenaline increase the effect of the sympathetic system:

• Increasing the performance of the heart by increasing its ability to contract;
• Promote glycogen breakdown in muscles and liver;
• Mobilization of fatty acids in adipose tissue;
• Dilation of blood vessels in skeletal muscles ;
• Narrowing of the blood vessels of the bowels ;
• Suppression of insulin secretion .

Via the hypothalamus - pituitary axes : On the one hand, the hypothalamus activates the sympathetic nervous system; on the other hand, it is the starting point for a cascade of hormones that intensify and expand the stress response: The hormones released by the hypothalamus are referred to as releasing hormons ( liberins ) because they are in cause the downstream pituitary gland to release corresponding hormones, the tropines . These hormones act again on other hormone glands, which in turn release hormones. These hormones act on their target organs while inhibiting the pituitary gland and hypothalamus. This ensures that a stress reaction can also be switched off again if there are no stressors.

Hormone cascade of the hypothalamus-pituitary-thyroid axis (HHS axis):
Hypothalamus → TRH → pituitary → TSH → thyroid → thyroxine

Thyroxine promotes oxidative metabolism in the long term (half-life 6 days) , increases body temperature and stimulates the sympathetic system.

Hormone cascade of the hypothalamus-pituitary-adrenal cortex axis (HPA axis):
Hypothalamus → CRH → pituitary gland → ACTH → adrenal cortex → cortisol

Cortisol activates the breakdown of glycogen in the muscles, the formation of new glucose in the liver and inhibits the release of hormones from the hypothalamus and pituitary gland.

The pituitary gland also produces endorphins , which reduce the sensation of pain and increase body temperature.

literature

• HW Krohne: The stress reaction. In: HW Krohne (ed.): Stress and coping with stress during operations. Springer-Verlag, Berlin / Heidelberg 2017, pp. 7–40.

Individual evidence

1. ↑ Walter B. Cannon: Anger, hunger, fear and pain: A physiology of emotions , from d. Engl. Transl. by Helmut Junker. Edited by Thure von Uexküll . Munich, Berlin, Vienna: Urban and Schwarzenberg 1975 (first English edition 1915)
2. ^ WB Cannon: Bodily Changes in Pain, Hunger, Fear and Rage: An Account of Recent Researches into the Function of Emotional Excitement , Appleton, New York, 1915 harvardsquarelibrary
3. ↑ Hans Selye: Stress. Rules of life from the discoverer of the stress syndrome. Rowohlt TB-V., Rnb. (May 1986) ISBN 978-3499170720 (including various books by H.Selye)
4. ↑ Taylor SE, Klein LC, Lewis BP, Gruenewald TL, Gurung RA, Updegraff JA: Biobehavioral responses to stress in females: tend-and-befriend, not fight-or-flight , Psycholical Review, Volume 107, No. 3S. 411-429, 2000 (review). PMID 10941275
5. ^ E. Aronson , TD Wilson, RM Akert: Social Psychology . Pearson study. 6th edition 2008. ISBN 978-3-8273-7359-5 , p. 504
6. ↑ Note: Compare also: Shelley E. Taylor, "Tend and befriend model" in the English language Wikipedia.
7. ↑ ^{a b} L. G. Sobrinho u. a .: Cortisol, prolactin, growth hormone and neurovegetative responses to emotions elicited during an hypnoidal state. In: Psychoneuroendocrinology , January 2003, 28 (1): 1-17. PMID 12445833
8. ↑ LG Sobrinho: Prolactin, psychological stress and environment in humans: adaptation and maladaptation , Pituitary, 2003, 6 (1): 35-39, PMID 14674722
9. ^ T. Theorell: Prolactin - a hormone that mirrors passiveness in crisis situations , Integr Physiol Behav Sci. 1992 Jan-Mar; 27 (1): 32-38. PMID 1576086