When an animal (man included) is confronted with a threat in the environment, a response is triggered to protect the animal from the danger. When the threat or danger is real and may lead to serious consequences to the wellbeing of the animal it leads to stress. Stress is defined “as an organism’s total response to environmental demands or pressures,” it is both a psychological and biological condition (Van der Kolk, 1996). In human beings, the response to the environmental threat depends on a number of factors which include personality, physical development and general health. Stress normally occurs when the adaptive ability of an individual is exceeded by the environmental threat (stressor). “During acute stress, the mind and body respond with a fight or flight responses that involve the activation of sympathetic nervous system and the release of stress hormones.” (Cooper, 1996)Psychological and biological stress models have been put forward to explain the events that take place when one is under stressful conditions. This paper will compare and contrast the two stress models by describing how each model defines “stress” and relates it to illness, homeostasis and stress hormones (particularly cortisol).
Biological stress model
Hans Selye (1907-82), was a Canadian scientist who discovered that people who were plagued by chronic diseases exhibited certain similar symptoms. Selye noticed that the symptoms were linked to stressful conditions; he set up experiments to test the hypothesis. He subjected rats to distinct physical stress factors which included; shock, heat, poison and sound. “The rats showed enlarged glands, shrunken thymus glands and lymph nodes, and gastric ulcers. Selye then developed the three Stage model of stress response. This model consists of alarm, resistance, and exhaustion.” (Cooper, 1996) The three stages outline the process he termed “the general adaptation syndrome (GAS).” (Petersen, 1975) The first stage (alarm) entails the production of adrenaline to stimulate the various response pathways after a threat (stressor) is detected. In the second stage (Resistance), the body activates mechanisms to try and adapt to the changes in the environment caused by the stressor. This is followed by the third stage referred to as exhaustion, this is the last stage of the GAS response model and is characterized by the “depletion of all the body’s resources” leading to inability of the body to function normally. “The early autonomic nervous symptoms may resurface (raised heart rate sweating, etc.).” (Clark, 1997) If stage the stage persists, long term impairment may result as the functional ability of glands, particularly the adrenal gland, the immune system is overstretched. “The outcome can manifest itself in obvious illnesses such as ulcers, depression, diabetes, trouble with the digestive system and even cardiovascular problems” (Clark, 1997). Other physical and mental problems will add on the list as the condition escalates further.
In stressful conditions, “the hypothalamus stimulates the activation of the sympathetic part of the autonomic nervous system and particular hormonal secretion from the pituitary gland.” (Horowitz, 1997) The hormones are meant to maintain homeostasis where by they enhance the body’s adaptive ability to the stressful conditions. The hormones released lead to; “increased heart and lung activity, flushing, stopping or slowing down of the gastric activity, constriction of blood vessels, liberation nutrients for muscular activity, dilation of blood vessels in the muscles, mydriasis and inhibition of the lacrimal gland.” (Petersen, 1975) Cortical, a hormone secreted by the adrenal cortex and that functions to regulate carbohydrate, protein and fat metabolism as well as maintaining the blood pressure during the stress response. Cortisol stimulates gluconeogenesis and inhibits the effects of insulin leading to increased blood sugar level. Under stressful conditions, the gluconeogenesis is vital for glucose generation for muscular activity.
According to Selye’s biological model, chronic illnesses result in stressful conditions. Stress leads to the overproduction of ACTH “which often lead to elevated levels of cortisal in the blood”. (Cooper, 1996) This will cause high levels of blood sugar and the high levels will in turn lead to conditions like obesity, diabetes in extreme cases the body’s immune system is compromised. Other conditions include gastric disorders, depression and other mental and physical conditions.
Psychological stress model
According to Lazarus’s psychological stress model, “a psychological situation is stressful if only it is appraised as such.” (Lazarus, 1976) Cognitive evaluation is important to ascertain if an environmental circumstance is potentially hostile, and may cause injury/damage or a challenge. The assessment (appraisal) occurs in two (primary and secondary stages), “the primary appraisal which is influenced by both person and environmental factors, and triggers the selection of coping processes. Problem-focused coping is directed at managing the problem, while 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.” (Lazarus, 1976) During the primary appraisal, Lazarus explains that there must be certain amount of threat in the environment to trigger the stress response. The stress, especially if prolonged leads to disorders such as psychosomatic disorders, anxiety depression, coronary heart diseases, immune suppression and other physical and mental problems.
Although the two models approach stress response differently, they both attribute stressful condition to the threats in the environment. The second similarity is that, the two models confirm that a person tries to find mechanisms of coping with the stress in the environment. Thirdly, both the psychological and biological models associate the stressful conditions to the development of certain “physical and mental disorders or illnesses.” (Cooper, 1996) Another similarity is that, both models are vague on the issue of personality, they do not explain why people of distinct personalities deal with stress differently.
The two models of stress response differ in a number of ways. First, Selye’s biological model does not put emphasis on the magnitude of threat that is necessary to lead to stressful conditions. In this model every amount of threat will lead to a stressful condition. It is only the adaptive mechanisms which differ with the variation in the potentiality of the threat to cause harm. While in the Lazarus psychological model there must be “cognitive evaluation to determine the magnitude of threat in the environment and its ability to elicit stressful conditions.” (Horowitz, 1997) The second difference is on exhaustion, in the biological model there is depletion of all the body’s resources leading to organ impairment. Whereas in Lazarus’s psychological model, a person or animal examines various available ways to cope with the situation and if one method fails he or she tries another. There is no giving up in the psychological model. The third difference occurs in the roles played by the mind and hormones during stress response; the psychological stress model emphasizes that, stress response process is mainly a function of the mind while the biological model attributes the response to hormones more than the mind. The fourth difference can be deduced from deterioration that leads to complications or illness, the psychological model attributes the complications to the effect of stress on the brain while the biological model attributes them to effects caused by hormonal imbalance and organ failure.
A lot of research has been done to determine the mechanisms that lead to stress and the response initiated to cope with it. Psychological and biological models have been constructed to explain the events that take place when a person is stressed. Both models have led to the generation of substantial knowledge on the stress issue. The biological stress model in particular, has led to understanding of the physiological processes that take place in trying to cope with threats in the environment. This model has explained the hormonal involvement during the stress response. The psychological model on the other hand has put much emphasis on the mind, asserting that it is the effect of stress on the brain that leads to other physical and mental complications. The model has created an association of stress to mental conditions such as anxiety and depression. However, its association of stress with physical disorders has not been satisfactory. But the Nevertheless, the two models have done exemplary to explain the stress response and now there is a general consensus on the issue. It is now known that cortisol plays a major role during stress response and is the hormone response for many conditions associated with stress.
Clark, R. B. (1997). Psychological Aspects of pediatrics and Psychiatric Disorders. Stamford: Appleton & Lange.
Cooper, C. (1996). Handbook of stress,medicine and health. Florida: CRC press.
Horowitz, M. (1997). Stress Response Syndromes: PTSD, Grief and Adjustment Disorders. Northvale,NJ: Aranson.
Lazurus, R. (1976). Patterns of Adjustment. New York: McGraw-Hill.
Petersen, C. M. (1975). Learned Helplessness: Atheory of the age of Personal Control. New Yok: Oxford University Press.
Van der Kolk, B. A. (1996). Traumatic Stress: The Effects of Overwhelming Experience on Mind, Body and Society. New York: Guilford Press.