Summaries and study services with Why Zebras Don’t Get Ulcers: The Acclaimed Guide to Stress, Stress-Related Diseases, and Coping by Sapolsky - Booktool
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In this chapter, a number of principles that are important for human functioning will be discussed.
In recent decades, much has changed in contemporary disease patterns. This is partly due to the progress in the development of medicines. Today, more people are dealing with heart failure and vascular disease than with infections and malnutrition. Associated with the change in disease patterns, diseases are also viewed differently. Scientists discovered that there is a strong link between our emotions and the biological processes in our body. Our thoughts, feelings and personalities influence these processes, causing two people who get the same disease to go through different disease courses. Stress also affects our health and can even make us feel ill. However, stress can lead to the body adapting in certain situations in order to survive.
There are also differences between humans and animals, especially in the way they experience stress. Animals experience stress in acute physical crisis situations. The body appears to be perfectly capable of dealing with this type of stress. People, on the other hand, often experience chronic physical stress. The body copes fairly well with this type of stress.
In addition to acute and chronic physical stress, there is a third form: psychological and social stress. This form of stress is characteristic of humans and actually only exists in our heads. People can experience strong emotions that are the result of just thoughts. Human bodies can respond in the same way to psychological and social stress as to physical stress. The human body can adapt very well to deal with acute stress that lasts for a short time. However, this is different when the stress appears to be chronic and we activate our stress system often and for a long time.
The body is not geared to chronic stress, because its physiological defense mechanisms are originally designed to enable the body to respond quickly and efficiently to a sudden threat. For some time the body will resist the psychological stress, but then exhaustion will inevitably follow. This can cause stress-related illnesses.
The body is constantly trying to reach a state of homeostasis. The body consists of different mechanisms and each mechanism has an optimal value. Homeostasis means that the body is completely in balance, so that all mechanisms have their optimal value. The body is always trying to achieve this balance. However, there are a number of things that take the body out of homeostasis. We call these stress factors and are events that take place outside the body. The body responds to this by means of a stress response, it will undertake activities to regain homeostasis.
However, a stressor does not have to be just what is happening right now. People can trigger a stress response by thinking about potential stressors. The stress response is therefore not only triggered by physical or psychological threats, but also in anticipation of them. This was first discovered by Selye about sixty-five years ago. Selye did a study in rats. His rats were injected daily with an extract from an ovary. However, being clumsy, they often fell and he had to search for them half the morning before he could inject them. At the end of the study, it was found that the rats had enlarged adrenal glands and stomach ulcers. To rule out that these symptoms were the result of the injections, Selye used a control group injected with saline solution. These rats, too, regularly fell to the ground and were chased by Selye in an attempt to get them. The control group showed the same symptoms as the experimental group, which led Selye to conclude that these physical symptoms were caused by the stress that arose when he chased the fallen rats.
Selye came to two conclusions:
The original concept of homeostasis was based on two ideas:
However, this concept turned out to be incorrect and has therefore been expanded to include the theory of allostasis. With regard to the first idea, this implies that there are different optimal levels depending on what you are doing. The optimal value for heart rate is much lower when you are sleeping than when you are training for the marathon. For the second idea, this means that there is not one way in which the ideal value can be reached, but that this can be done in different ways. Each way has its own consequences.
Roughly speaking, the difference is that homeostasis in a deficiency only appeals to the responsible mechanism and that allostasis causes the brain to bring about changes throughout the body, and often also in the behavior of a person.
Incidentally, the body does not have to stop all complex regulatory processes in order to restore a certain value. In addition, the body is able to anticipate values that will deviate from their optimal level. The brain can already control certain bodily functions, which will ensure that a certain value will not lose its optimal level. This is in line with the fact that the body can react to a stressor before it actually takes place.
In the theory of allostasis, a stress factor is seen as anything that takes you out of your allostatic balance and the stress response as your body's attempt to restore allostasis. Although it is common to think that specific challenges for the body require specific adjustments, each stressor triggers the same stress response.
In humans, the core of the stress response lies in the fact that the muscles in the body have to work much harder than normal. Firstly, glucose must be mobilized, which provides energy. The glucose is then transported through the body at lightning speed by increasing the heart rate, blood pressure and respiration. The sympathetic system is activated, while other processes in the body are stopped. Examples of this are digestion, growth and reproduction.
The immune system will also be temporarily suppressed. The energy that is saved with this will be used to make the sympathetic system work harder. The parasympathetic system is temporarily turned off. Pain perception can also be turned off during acute stress.
During acute stress there is also a change in cognitive and sensory skills. Improve certain parts of the memory, so you can quickly remember whether you have been in a similar situation before and how to get out. In addition, your senses become sharper.
Selye developed a three-phase theory of stress responses:
In the third phase, however, Selye made the mistake of thinking that you got sick because the hormones that are secreted during the stress reactions ran out. However, this cannot be the case because these hormones are so crucial that individuals will never run out. The stress response can have a harmful effect on the body if it is sufficiently activated. The stress response is especially harmful if the stress factor is psychological. Especially with long-term (psychological) stress and when you often suffer from stress, the consequences can be major. Because you release your energy so often in response to the stress, the body does not have time to recover and rebuild reserves and the body will become exhausted more quickly. People who are under chronic stress are also more likely to suffer from:
When you are under a lot of stress and therefore often secrete stress hormones, it is every time more difficult to find the balance of allostasis. The following problems can arise:
Having a stress response is important, as shown by studying people who don't have the stress response because of an illness. Two such diseases are:
In these diseases, two important hormones for the stress response are not secreted.
If you repeatedly activate your stress response or have difficulty turning the stress response off when the stressful situation is over, it is possible that the stress response is ultimately harmful to the body. However, it is not the stress or the stressor that makes you sick. Chronic stress factors or stress factors that come back often only increase the risk of becoming ill. They also increase the likelihood that defense mechanisms cannot cope with a disease properly. There are several steps between getting a disease and actually getting sick. This also creates individual differences.
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