It seems difficult to define a situation as stressful without taking into
account the responses of the people who might be involved. The degree of stress
a particular environment might cause has to be seen as a spectrum. There is no
doubt that, for most people, walking down the meridian of a freeway to look for
a gas station would be stressful, while watching a sunset from a flower-strewn
mountain meadow would have little inherent stress, unless it's June and you
Stress as a Response
The second category of physiological theory we'll look at views stress
as the response to an adverse, or stressful, situation. This approach is based
on the work of the physiologist Hans Selye. Selye theorized that the stress
response is a built-in mechanism that comes into play whenever demands are
placed on us, and is therefore a defense reaction with a protective and
adaptive function. In other words, there is a general physiological reaction to
all forms of stress, which usually acts in our own best interests. Selye called
this reaction the General Adaptation Syndrome (GAS). This theory
suggests a three-stage process of response:
- An alarm reaction.
- A resistance stage, which represents a functional recovery of the
body to a level superior to the pre-stress state.
- An exhaustion reaction, in which there is a depletion and breakdown
of the recovery of stage 2, due to continuation of the stressful situation.
The limitation of this inflexible physiological model of stress is that it
ignores the purely emotional or mental factors that can produce a wide
variation in the way we respond to potentially stressful situations.
Stress as a Perceived Threat
Much recent research suggests that specific situations or objects are
threatening to us because we perceive them as such, rather than because of any
inherent characteristics. According to this category of research, stress occurs
when we cannot cope with or adjust to the demands made on us-when it all
becomes too much. The degree of stress is partially affected by what is going
on in general, but is more intimately connected with how we perceive the
factors involved and how we are feeling at the time.
Responses to Stress
There is now a large body of research about both the physiological and
the psychological responses to stress. It is easier to explore these responses
separately, as we'll do here, but keep in mind that they need to be looked at
in conjunction with each other in order to be fully understood.
The regulation of physiological responses to threats or stressful
demands is handled mainly by the adrenal gland. Immediate response is
controlled mainly, though not completely, by the adrenal gland's central
medulla, while long-term response is handled by the surrounding cortex. The
initial response-preparing the body for what has been called the
- Increased nervous-system activity.
- Release of adrenaline and/or noradrenalin into the blood stream by the
adrenal medulla. These hormones support the nervous system through metabolic
activity. The body's response to these chemicals includes:
- increase in heart rate and blood pressure.
- surface constriction of blood vessels, so that the blood leaves the skin to provide the muscles with more sugar and oxygen (which is why we go white with shock).
- mobilization of the liver's energy reserves through the release of