•Hans Selye expanded on Cannon’s conceptions in two ways. First, he noticed that corticosteroids,
which are released by the adrenal cortex (or top layer of the adrenal glands), are also elevated in
response to a wide variety of stressors.
•Glucocorticoids are fat-soluble molecules, which enables them to cross cell membranes in every
organ system in the body. Thus, they have a wide range of effects. Thus, stress can affect the
functioning of nearly every organ system in the body, either through SNS or HPA activation.
•Second, Selye expanded Cannon’s dualistic processes (SNS vs. PNS activation) by describing three
stages in reaction to stress.
oThe alarm stage is similar to Cannon’s fight/flight reaction but involves the adrenal glands as
well as SNS activation.
oThe second stage was adaptation- in which there is a return to physiological homeostasis (due
to PNS activation)
oThird stage, exhaustion, the organism may fall ill or die if the stress continues [hormones
•Both Cannon and Seyle argued that there are general responses to stress, but it is now widely
recognized that there are individual differences in stress reactions.
•From a psychosocial perspective, studies investigating the effect of stress on sympathetic arousal,
including heart rate, respiratory rate, and galvanic skin response (a measure of the degree to which the
electrical conductance of the skin is affected by sweating) consistently found individual differences in
the patterning of sympathetic arousal.
•In addition, it is now recognized that activation of the HPA axis is an attempt to buffer the rather
damaging influence of prolonged SNS activation.
•SNS activates immune system responses, encouraging inflammation; HPA activation suppresses the
•In addition, we now know that most, if not all, of the endocrine hormones are affected by stress,
increasing or decreasing in fairly complex temporal patterns.
•In general, stress activates those hormones that increase metabolic functioning and suppresses those
involved in long-term growth and maintenance.
•The recognition of broader endocrine responses to stress has led to an argument for a third stress
pathway, through oxytocin.
•Oxytocin is a hormone that is very important in reproductive activities such as breast-feeding.
•It may also mediate social relations, and evidence has been provided that it might underlie sex
differences in stress reactions.
2. Stress and the Development of Chronic Illness
•Stress can results in heart disease
•Risk factors: blood pressure, cholesterol, atherosclerotic, and arteriosclerotic process, and immune
functioning, tumor proliferation, suppress natural killer (NK) cells
•Allostasis- fluctuation in physiological systems to meet external demands
•Allostatic load- the physiological costs of chronic exposure to fluctuating or heightened neural or
neuroendocrine responses that result from repeated chronic environmental challenges
Positive Physiological Changes