Protocols for measurements that actually cause stress have little value; is one
measuring the individual’s current stress or creating the stress that is being quan-
tified? One example is the use of venipuncture to obtain blood samples.
Venipuncture stimulates a marked increase in sympathetic nervous system activity
and leads to an increase in plasma catecholamine (epinephrine and norepinephrine)
levels by over 50% (Carruthers et al. 1970 ; Brown 2007 ).
The most direct measures of stress would somehow tap into the brain activities
involved with stress appraisal. This is not possible for studies that involve people
doing normal activities. The next most direct measures would examine the markers
of brain activity that“spill over”into other parts of the body: for instance, the
presence of catecholamines in the blood (Esler 1993 ; Brown 2007 ). Again, the
problem of obtaining adequate samples of blood without actually being a cause of
stress impedes the ability to use these direct measures. Human biologists have
instead used more indirect measures of stress appraisal, such as urinary cate-
cholamines, urinary or salivary cortisol, cortisol deposited in hair, and salivary
alpha-amylase—an indicator of sympathetic nervous system activity (Ice and James
Cortisol
Epinephrine
Norepinephrine
Stressor
(stimulus)
Cognitive Brain
Centers
Amygdala
Sympathetic
Nervous System
and Adrenal
Medulla
Brain/
Spinal Cord
Stress induced
analgesia
Circulatory
System
Increased heart rate,
stroke volume, blood
pressure
Increased ventilation, Lungs
Bronchial dilation
Vasodilation Muscle
Glycogenolysis, Liver
gluconeogenesis
Pituitary Adrenal
Cortical System
Immune
System
Inhibition of
T cells; reduced
inflammation
Sweat
Glands
Increased sweat
production
Hypothalamus
Fig. 7.2 A simplified diagram of the physiological stress response (after Brown 1981 )
122 D.E. Brown