CHAPTER 5 Defining and Measuring Stress. The Nervous System and the Physiology of Stress The nervous system is made-up of neurons (nerve cells) that provide.

CHAPTER 5

 Defining and Measuring

Stress

The Nervous System and the Physiology of Stress

• The nervous system is made-up of neurons (nerve cells) that provide internal communication by releasing chemical neurotransmitters across the synaptic cleft (the space between neurons). The billions of connections among neurons provide for complex actions. The nervous system is divided into the central nervous system and the peripheral nervous system. The central nervous system consists of the brain and spinal cord and all the other nerves in the body are in the peripheral division (see Figure 5.1).

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The Peripheral Nervous System

The peripheral nervous system is also divided into two divisions, the somatic nervous system, which consists of the nerves that activate voluntary muscles in the body. The autonomic nervous system (ANS) serves internal organs and glands and works automatically. Although conscious control of autonomically controlled reactions is possible, this control requires training.

The ANS is also divided into two parts, the sympathetic and parasympathetic divisions (see Figure 5.2). These two divisions act reciprocally, the sympathetic increasing its activity in emergency or stress situations and the parasympathetic acting in normal situations.

Neurotransmission in the ANS is conducted mainly by two chemicals, acetylcholine and norepinephrine, which exert complex effects.

The Neuroendocrine System

The endocrine system consists of ductless glands, and the neuroendocrine system consists of endocrine glands controlled by the nervous system. These glands release hormones that travel through the blood and act on target organs (see Figure 5.3).

1. The Pituitary Gland

The pituitary gland is located in the brain and releases a number of hormones that affect target organs in many parts of the body. One pituitary hormone—adrenocorticotropic hormone (ACTH)—acts on the adrenal glands.

2. The Adrenal Glands

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• The adrenal glands are located on top of the kidneys and contain two structures that produce different hormones, the adrenal cortex (outer covering) and the adrenal medulla (inner structure). The adrenocortical response occurs when ACTH stimulates the adrenal cortex to secrete glucocorticoids, the most important of which is cortisol. The adrenomedullary response is activated by the sympathetic nervous system and secretes catecholamines, including epinephrine and norepinephrine.

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The Physiology of the Stress Reaction

• The stress reaction mobilizes body resources in emergency situations. One route occurs through activation of the sympathetic nervous system, which is called the adrenomedullary response. The other route is through the hypothalamic-pituitary-adrenal axis and involves all these structures. The response of the hypothalamus prompts the pituitary to stimulate the adrenal cortex to produce glucocorticoids, including cortisol. (See Figure 5.4 for these two routes of activation.)

Maintaining an appropriate level of activation calls for varied levels of activation of the peripheral nervous system. This process is called allostasis, but prolonged activation of the sympathetic nervous system creates allostatic load, which may cause problems.

Shelly Taylor and her colleagues have proposed that this “fight or flight” model may be more appropriate for men; women may manage stress through a “tend and befriend” strategy.

Theories of Stress

Hans Selye and Richard Lazarus proposed influential theories of stress.

A. Selye's View

Selye's theory defined stress as a nonspecific or generalized response to a variety of environmental stressors. Whenever the body encounters a disruptive stimulus, it mobilizes itself in a generalized attempt to adapt to that stimulus.

1. The General Adaptation Syndrome

This mobilization is called the General Adaptation Syndrome (GAS). The GAS has three stages—alarm, resistance, and exhaustion. The potential for trauma or illness exists at all three stages (see Figure 5.5).

2. Evaluation of Selye’s View

Selye concentrated on the physiological aspects of stress, downplaying the psychological ones, and ignoring the perceptual and interpretative processes that can moderate the human experience of stress.

II.  B. Lazarus's View

Richard Lazarus saw a person's perception of an event as more important than the event itself. His transactional view emphasizes psychological factors (such as cognitive mediation), appraisal, vulnerability, and coping.

1. Psychological Factors

Lazarus held that people are harmed by negative life events only if they perceive those events as being personally important, are in a vulnerable state, and believe that they lack the ability to successfully cope with those events.

2. Appraisal

Lazarus and his associates recognized three kinds of appraisal—primary, secondary, and reappraisal. Primary appraisal is one's initial judgment of an event, which may be seen as (1) potentially harmful, (2) threatening or damaging to self-esteem, or (3) personally challenging. Secondary appraisal is one's perceived ability to cope with harm, threat, or challenge. Reappraisal of an event is ongoing as the situation is constantly being reevaluated.

3. Vulnerability

Stress is most likely to be aroused when people are vulnerable; that is, when they perceive a lack of resources to cope with a situation of some personal importance.

4. Coping

Coping involves our constantly changing efforts to manage both internal and external demands that are appraised as taxing or exceeding our resources. Coping is enhanced by such resources as health, energy, high self-efficacy, problem-solving skills, social skills, and social support.

A. Methods of Measurement

Stress has been measured by several methods, but most fall under two groups: (1) physiological measures and (2) self-reports, which may be either life events scales or daily hassles scales.  

1. Physiological Measures

Blood pressure, heart rate, galvanic skin response, respiration rate, and biochemical measures such as cortical and catecholamine release are some of the physiological indexes used to assess stress. A disadvantage of these procedures is that the equipment and the setting may themselves produce stress. 

2. Life Events Scales

Most life events scales are patterned after the Holmes and Rahe Social Readjustment Rating Scale, an instrument that emphasizes change in a person's life. The scale lists 43 life events arranged in rank order from most to least stressful. Respondents check the items they have experienced during a recent period, usually the previous 6 to 24 months.

Other stress inventors include the Undergraduate Stress Questionnaire (USQ), which introduced this chapter. The USQ is a self-report similar to the SRRS in that it provides a list of sources of stress and asks college students to check the ones that have happened to them during the past two weeks. Most items are hassles rather than major life events. The Perceived Stress Scale, which emphasizes perception of events, is a 14-item scale that attempts to measure the degree to which situations in people's lives are appraised as unpredictable, uncontrollable, or overloading. The scale assesses three components of stress: (1) daily hassles, (2) major events, and (3) changes in coping resources.

3. Everyday Hassles Scales

Lazarus pioneered scales that measure daily hassles rather than major life events. The original Daily Hassles Scale assumes that only unpleasant events (hassles) can be stressful; pleasant events (uplifts) may help reduce stress and even promote health. A companion measure was the Uplifts Scale, made up of items that might make a person feel good. Both scales emphasized the person's view of the event. Later, Lazarus and his colleagues published the revised Hassles and Uplifts Scale, a shorter scale that allows participants to see an event as either a hassle or an uplift. Specialized versions of hassles scales have also been developed. Table 5.1 in the text presents information on a variety of self-report inventories.  

B. Reliability and Validity of Stress Measures

The reliability of self-report inventories of stress is most often determined by having people fill out the instrument a second time at a later occasion, or by having a close associate—such as a spouse—fill out the inventory as if answering for the subject. Although most self-reports inventories have acceptable reliability, their validity to predict illness remains to be established.