- Homeostasis is the process of maintaining a constant internal environment despite changing external
conditions. Stress is the body’s response to a perceived threat to homeostasis. It is the body’s attempt
to re-establish homeostasis. The stressor is the perceived threat. They are characterized as events or
situations that trigger coping adjustments such as, exams or a ﬁrst date. Stress is a state of threat to
this equilibrium, and adaptation to stress, or allostasis, confers a survival advantage. Successful
adaptation requires not only the ability to respond to stress, but also the ability to control the stress
- Acute stress is a short-term type of stress that can be either positive (eustress) or distressing. This is
the most common occurring type of stress. Chronic stress is long-term stress.
- 2 stages of fight/flight response: Sympathetic adrenomedullary system (SAM) and Hypothalamic
pituitary adrenocortical axis (HPA).
- Short Term Fight/Flight Response (SAM Sympathetic Adreno Medullary) Axis
- The SAM or Short-term response is the primary system that is triggered within us in response to short-
term threats. This is a reflex response, which is electrically triggered. Electrical impulses from the
hypothalamus travel along nerves that directly connect to the adrenal and stimulate the release of
stress hormones adrenaline and noradrenaline/epinephrine. The body can’t sustain this short-term
fight/flight response for long because it would become exhausted. If the stressor is a more chronic one
then this triggers the secondary, longer-term fight/flight response to take over.
- 2. Long Term Fight/Flight Response (HPA Hypothalamic Pituitary Adreno Cortical) Axis
- The longer-term fight/flight response is triggered hormonally. This time the hypothalamus secretes a
hormone called CRF (Corticotrophin Releasing Factor), which stimulates the pituitary gland to produce
ACTH (Adrenocorticotropic Hormone), which in turn stimulates the adrenal cortex (outer part of the
adrenal glands) to release stress hormones like cortisol. This longer-term fight/flight response is
affected by our perception of the event, which decides the type and amount of stress hormones that are
secreted. Research has shown that chronic activation of this longer-term HPAC fight/flight response
can be a factor in causing a number of psychological and physiological health problems (dysregulation
in cortisol levels).
Stress and inflammatory response - Cohen et al (2012)
Purpose: Investigated a model in which chronic stress results in glucocorticoid receptor resistance, which in
turn impairs ability to regulate inﬂammatory response.
GCR refers to a decrease in the sensitivity of immune cells to glucocorticoid hormones that normally terminate
the inﬂammatory response.
Here we test the model in two viral-challenge studies.
In study 1, we assessed stressful life events, GCR, and control variables including baseline antibody to the
challenge virus, age, body mass index (BMI), season, race, sex, education, and virus type in 276 healthy adult
volunteers. The volunteers were subsequently quarantined, exposed to one of two rhinoviruses, and followed
for 5 d with nasal washes for viral isolation and assessment of signs/symptoms of a common cold. In study 2, we assessed the same control variables and GCR in 79 subjects who were subsequently exposed
to a rhinovirus and monitored at baseline and for 5 d after viral challenge for the production of local (in nasal