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Stress Response of Humans

Introduction to Neuroscience 

For Mental Health Professionals

Overview of the Stress Response in Humans

Diathesis and Stress Interaction


Diathesis: is the predisposition (genetics) of the human body to disease or disorder


Stress: is the term which refers to the factors in the environment: which offer challenge, distress, problems to solve, which are unique to each individual and as a result are the environmental condition which elicit disease or disorder in the individual or are the conditions in the human which are ripe for the disease or disorder.


Definition of Stress

Stress as a process involves environmental event (a stressor); its appraisal by the individual; various responses of the organism; reevaluations resulting from responses and changes in the stressors.


Depends on the quality of an external stimulus

Depends on the response to such stimulus

Depends on the results from interaction between stimulus and response


Physiological Effects of Stress

Sympathetic Nervous System (system responsible for mobilizing body resources in urgent situations) stimulate the adrenal medulla of the adrenal glands

The adrenal stimulation results in production of catecholamines, Epinephrine and Norepinephrine, affecting the body’s heart rate, respiration, blood flow and muscle strength.

Stress causes the pituitary gland (structure connected to hypothalamus in forebrain) to release the andreno-corticotropic hormone (ACTH).

ACTH stimulates the adrenal cortex of the adrenal gland to secrete glucocorticoids. The most important of the glucocorticoids is cortisol which mobilizes the body’s resources by increasing energy and decreasing inflammation especially in injuries.

Negative Impact of Prolonged Stress Response


There is a negative impact on the body’s organs, mental functioning and Immune system

There is an impact on the immune system which impedes the immune system from destroying viruses, bacteria, tumors, and irregular cells

Stress impacts immunosuppression and  it is an important influence on health and illness of the individual

Hormone Stress Cascade during Severely Stressful or Traumatic Events

1. Hypothalamus is activated by messages from nervous system or blood stream during a “stressful event” and it releases CRH which initiates the fight-flight response.

2. Corticotrophin-releasing hormone (CRH) is a polypeptide hormone secreted by the hypothalamus into the pituitary portal system where it triggers the release of adrenocorticotropic hormone (ACTH) from the pituitary gland. During stress it surrounds the pituitary gland which then releases ACTH.

3. Adrenocorticotropic Hormone (ACTH) stimulates the adrenal glands to release Cortisol and Adrenalin

4. Cortisol and Adrenalin increase heart rate and metabolic rate

ACTH - Adrenocorticotropic Hormone

ACTH stimulates the adrenal cortex of adrenal gland to secrete glucocorticoids. Most important of glucocorticoids is cortisol which mobilizes body’s resources by increasing energy and decreasing inflammation especially in injuries.


ACTH triggers “survival hormones” during the stressful event especially Cortisol until the threat is removed.


With long-term stress or constantly repeating triggers such as with re-experiencing the hormone release does not shut down



Cortisol is an aging hormone

Elevated amounts of Cortisol damages the hippocampus which results in accelerated aging responses throughout the body.

An elevated amount of Cortisol leads to depression and feelings of fatigue


The Hippocampus is involved in learning and memory

Damage to the hippocampus causes memory problems and interferes in new learning and even current memory.

Victims of PTSD have been found to have smaller hippocampuses-the more memory problems they had the smaller was their hippocampus

Adults who have been severely physically and/or sexually abused have similar memory problems with reduced hippocampus

Smaller hippocampus does result in dissociative symptoms-greatest decrease in volume of the hippocampus correlates to most pronounced symptoms of dissociation

Depression is also associated with reduced hippocampus size

Bilateral response of brain to stress and trauma

Major stress and trauma are right side of brain activity – rich in images of the stressor and trauma

The left side of the brain which involves talking shuts down in severe stress and trauma. The bracus area of the brain on the left side of the brain becomes unresponsive under severe stress and trauma and individuals are heard to say: “I don’t have words to tell you what I have experienced.”

There is a need to help both sides of the brain to recover from the stress and trauma so there is a need for bilateral processing similar to used in EMDR

It is important to realize that humans use their body to help their brain think through things and to process the stress and trauma