The Biological Effects of Stress

The first three modules in this unit have discussed conflict, frustration, and anxiety. These are all factors in stressful situations. In this module, we will consider the effects of such psychologically stressful situations on the human body. We will also examine the effects of prolonged stress.

As you read the text, try to answer the following questions.

Stress is brought about by any condition that increases activity. This includes a great deal of ordinary living, such as many forms of work and recreation. However, extreme stress may damage the organism. Physical injury, invasion of the body by germs, exposure to extremes of heat or cold, and excessive fatigue, all bring about stress. They all threaten to damage the organism.

Stress accompanies a threatening situation

In psychological stress, however, the threat of damage may be either real or imagined A soldier's fear in battle is centered around the threat of being wounded. The angry man who wants to fight back against an insult feels the threat of being hurt in the fight that may ensue. Stress is also felt by a student who fears being called on in class when he has inadequately prepared his assignment. Severe and prolonged psychological stress can cause actual physical damage to the organism. Hence, the imagined threat of damage to the organism, as in the case of the fearful soldier or of the man who does not get along with his co-worker, may have real consequences.

Another definition of stress will help to pinpoint its psychological aspects. Stress is an internal state resulting from the anticipation of an impending harmful event which threatens to be more than one can cope with. The harmful event may be either psychic or environmental. It may be in the form of a conflict situation in which the individual is faced with a difficult decision. Or the harmful event might be in the form of a frustrating situation in which the individual finds a barrier between himself and his goal.

Two important factors related to stress, therefore, are conflict and frustration. Another important kind of stress is that associated with anxiety, which may itself be an outcome of frustration or conflict.

The bodily changes that take place as a result of anger or fear mobilize the body's energy to deal with the emergency situation producing the emotion. In the case of chronic anxiety or hostility, however, the accompanying changes persist, and these can have damaging effects on the organism.

Constant pressure for action produces stress

A dramatic illustration of the biological effects of chronic tension due to stress is provided by Brady's experiments (1958). In one of these experiments, pairs of monkeys were confined in restraining chairs and administered electric shocks at 20-second intervals. Both monkeys had identical levers and lights which warned them when a shock was imminent. However, only one of these levers, when pressed every 20 seconds, served to prevent or turn off the shock. This lever was controlled by the "executive" monkey, while that of his companion was not connected to the shock mechanism. The result was that only the executive monkey developed ulcers. Both monkeys received the same number of shocks, so that factor of physical discomfort was not critical. It was the combination of discomfort with contingent avoidance responses that resulted in stress. In this experiment the stress was great enough to produce a psychosomatic (or psychogenic) illnessÄgastric ulcers.

The consequences of prolonged stress have been the particular interest of Hans Selye, a biologist at the University of Montreal. Selye (1956) studied the effects on various animals of many kinds of prolonged stress such as exposure to cold and the injection of poisons. He found an invariable pattern of physical response to prolonged stress. He named this pattern the general adaptation syndrome. This response pattern is comprised of three stages.

The first is the stage of alarm-reaction. A state of initial shock (reduced activity) is followed by overmobilization of forces within the organism to meet the shock. In this stage the organism responds as to fear or anger. The endocrine glands become active. The adrenal glands become enlarged as they produce more adrenalin and discharge their stored-up supply of steroids. This intense activity of the adrenal glands results in many other changes in the body.

The second stage of the general adaptation syndrome is the stage of resistance. After a few days of prolonged stress, the organism seems to adapt to the stress and return to normal. The adrenal glands return to their usual size and color, and their supply of steroids is renewed. Blood sugar and salt levels also return to normal.

The stage of exhaust/on is the third and final stage. The acquired adaptation to the stress is lost. In this stage the adrenal glands again become enlarged. The kidneys become damaged as a result of the oversecretion of hormones, and the animal eventually dies.

Selye also found that animals in the second, "resistance," stage were not so normal as they seemed. If a second stress were added at this stage, the animals quickly died. This seemed to indicate that they had exhausted their defenses in adapting to the original stress and had none left to deal with additional stress.

Physical damage comes more from prolonged stress than from sudden fear

Selye's general adaptation syndrome is useful in describing what happens to the organism in response to stress of a psychological origin. The last stage (the stage of exhaustion) is seldom experienced, however, by persons undergoing prolonged psychological stress. It is the second, "resistance" or "adaptation," stage which is particularly applicable. Brady's "executive" monkeys showed an increase in stomach acid, with consequent tissue damage, during the rest periods, when adaptation was taking place. There was no increase in acid during the periods of acute stress (alarm-reaction stage). Similarly, during the war, people who underwent intense aerial bombardment developed bleeding stomach or duodenal ulcers a few days later. The sequence of events is consistent with the fact that, although acute fear reduces the flow of stomach acid, chronic fear or tension increases it.

A chronic state of stress, whether physical or psychological, has damaging effects. The general adaptation syndrome indicates that the endocrine glands provide the mechanism for psychosomatic disorders resulting from prolonged stress.


Now test yourself without looking back.

1. Stress can be produced by____________________________________, or ________________________________

2. The term "general adaptation syndrome" was coined by Selye as a label for the invariable pattern of:
a. physical response to acute stress.
b. psychological response to acute stress.
c. physical response to prolonged stress.
d, (none of these)

3. Number the stages of the general adaptation syndrome in the order in which they occur.

a. Resistance___________

b. Exhaustion___________

c. Alarm-reaction________

4. In the third stage of the general adaptation syndrome, the acquired adaptation to stress on the part of the organism is:
a. lost.
b gained.
c. regained.
d. not needed.

5. What happened to an animal in Selye's experiment if, during the "resistance" stage, another kind of stress was added to the first?



Hans Selye described the pattern of physiological responses of the organism when it undergoes severe and prolonged stress. He called this pattern the general adaptation syndrome. Selye recognized three distinct stages: an'`alarm-reaction,' stage in which the organism mobilized all its forces to meet the threat, a "resistance" stage characterized by apparent return to normality, and an "exhaustion" stage in which the acquired adaptation is again lost.

By the term "general adaptation syndrome" Selye meant:

a. the physiological response pattern that develops in an organism under extreme and long-continued stress.
b. the physiological response pattern of an organism under acute and extreme stress.
c. the physiological response pattern of an organism which is about to die.
d. (none of these)


1) Alarm-reaction stage (initial physiological responses to extreme and long-continued stress)_________

2) Stage of resistance (apparent adaptation to stress)__________

3) Stage of exhaustion (final reaction to long-continued stress in which physiological changes reappear in acute form)_________

a. Adrenal glands return to normal and their supply of steroids is renewed. Blood sugar and salt levels are also normal.

b. Endocrine glands become very active. Adrenal glands become enlarged and discharge their steroids.

c. Acquired adaptation is lost. Kidney damage occurs.

Stress is defined as an internal state brought about by an environmental situation that threatens to damage the organism. Which of the following could cause stress?
a. Conflict
b. Frustration
c. Anxiety

When animals in the "resistance" stage of the general adaptation syndrome were submitted to another kind of stress, they quickly died. This indicated that:
a. the organism had not made any adjustment to stress in the "resistance" stage.
b. although the organism seemed to have adapted to stress, it had exhausted all its defenses.
c. the second kind of stress was worse than the first.
d. (none of these)
________________________________________ 2

In Brady's experiment in stress-induced ulcers, which monkeys developed ulcers?

Selye described the pattern of physiological responses to severe and prolonged stress as the _______________________________________________________________3



1 b, c
2 b
3 general adaptation syndrome
4 alarm reaction stage
5 a, b, c
6 a
7 The "executive" monkeys
8 1) b
2) a
3) b, c


1. The physical response pattern that develops in an organism under extreme and prolonged stress is called the _________________________________________________________________

2. Of particular interest to Selye were the effects of:
a. anxiety.
b. adrenalin.
c. acute stress.
d. chronic stress.

3. The endocrine glands serve as the mechanism that produces psychogenic physical ailments during periods of:
a. acute stress.
b. no stress.
c. chronic stress.

4. Selye's animals who were in the "resistance" stage of the general adaptation syndrome quickly died when they were submitted to yet another kind of stress. This indicated that:
a. the second kind of stress was more severe than the first.
b. the organism does not adjust to stress in the "resistance" stage.
c. although the organism seemed to have adapted to stress, it had exhausted all its defenses.
d. (none of these)

5. Write the stages of adaptation after each group of symptoms.

a. Blood sugar and salt levels are normal. Adrenal glands return to normal and their supply of steroids is renewed.______________________________

Acquired adaptation is lost. Organism may die.________________________

Endocrine glands become very active. Adrenal glands become enlarged and discharge their stored-up steroids._______________________________


Unit 10 Table of Contents

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Oct. 27, 2005