Let’s learn about the pathophysiology of stress.
According to the endocrinologist, Hans Selye, stress is “the non-specific response of
the body to any demand placed on it.”
Stress can also be thought of as the body’s response to a harmful threat that can affect
the normal functioning of the body.
We will take a look at how stress affects the nervous and endocrine systems.
A number of nervous system structures produce specific responses to stress.
The autonomic nervous system activates the sympathetic portion in response to stress.
The sympathetic nervous system secretes epinephrine (adrenalin) that produces a fight or flight
response that includes: Increase heart rate and blood pressure
Increase breathing rate Pupil dilation
Increase blood flow to muscles, lungs and heart
Decrease digestion
The cerebral cortex responds to stress by: Increasing processing of the threat through
intense focus, planning, and attention.
The Thalamus responds to stress by increasing sensory input including the special senses
of hearing, vision and smell.
The hypothalamus responds to stress by secreting stress related hormones.
The limbic system responds to stress by: Creating an emotional response including anxiety,
fear, excitement, and anger along with activating the reticular activating system which increases
muscle tension and alertness.
The endocrine system also responds to stress by secreting hormones.
One of the important stress hormones is cortisol.
Cortisol is a steroid hormone secreted by the adrenal gland, particularly the adrenal
cortex.
The adrenal cortex responds to adrenocorticotropin hormone (ACTH) which is secreted by the anterior
pituitary gland.
The anterior pituitary gland secretes ACTH in response to corticotropin releasing hormone
(CRH) secreted by the hypothalamus.
Cortisol works to regulate blood glucose by promoting the conversion of non-carbohydrate
substances such as fats and proteins to glucose.
This works to provide additional energy to muscles.
Cortisol also has anti-inflammatory properties and can suppress the immune system.
Other hormones secreted in response to stress include the catacholamines epinephrine, norepinephrine
and dopamine which are secreted by chromaffin cells in the adrenal medulla.
The sympathetic nervous system stimulates these cells to secrete hormones.
The catecholamines have a similar effect on the body as sympathetic nervous system.
One way to describe the body’s stress response is the General Adaptation syndrome.
The General Adaptation syndrome has 3 stages: During the alarm stage, catecholamines and
cortisol are secreted by the neuroendocrine system (adrenal gland and hypothalamic-pituitary
axis) and activate the sympathetic nervous system’s fight or flight response.
Thyroid hormones, growth hormone and reproductive hormones are suppressed during this stage
to conserve energy.
Secretion of Antidiuretic hormone (ADH) increases to conserve fluid volume and maintain blood
pressure.
If stress continues the alarm stage is followed by the resistance stage.
During this stage, cortisol levels decrease due to negative feedback.
In early stages of stress, cortisol is helpful in producing more energy.
However, if stress continues, increased cortisol secretion becomes harmful to the body by causing
immune system suppression, increased blood glucose and lipids, and breakdown of body
tissues.
The decrease in other hormones such thyroid, growth and reproductive hormones can also
have long term effects on metabolism and can lead to hypertension.
The exhaustion stage follows the resistance stage.
During this stage, degeneration of cells and tissues occurs and causes significant detrimental
changes in overall health.
Long term stress can adversely affect all of the body organ systems.
I hope you have learned something about the pathophysiology of stress, and, see you next
time.