Understanding how the body responds to stress

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Stress is a biological and psychological response experienced when confronted with a situation we believe we lack the tools to deal with.

A stressor is a stimulus (or danger) that induces stress, such as an exam, divorce, the death of a loved one, moving, or job loss.

Sudden and intense stress usually results in:

Heart rate increase
Increase your breathing rate (lungs dilate)
Reduced digestion activity (doesn’t feel hungry)
For energy, the liver discharged glucose.

First, our body evaluates a scenario to determine whether or not it is stressful. This judgment is based on sensory input and processing (what we see and hear in the system), as well as stored memories (i.e., what happened the last time we were in a similar situation).

When a stressful scenario is identified, the hypothalamus (located near the base of the brain) is engaged.

The hypothalamus controls the stress response in the brain. When the stress response is activated, messages are sent to two other structures: the pituitary gland and the adrenal medulla.

The Fight or Flight Response generates these short-term responses via the Sympathomedullary Pathway (SAM). The Hypothalamic-Pituitary-Adrenal (HPA) axis regulates long-term stress.

The hypothalamic-pituitary-adrenal (HPA) system responds to chronic stress.
The HPA (Hypothalamic-Pituitary-Adrenal) System
Pituitary-Adrenal (PAD) System
The stressor causes the Hypothalamic Pituitary Axis to fire.

The hypothalamus stimulates the pituitary gland.

Adrenocorticotropic hormone is secreted by the pituitary gland (ACTH)

ACTH stimulates the adrenal glands to create the corticosteroid hormone.

Cortisol allows the body to keep blood sugar levels stable.

Adequate and consistent blood sugar levels assist a person in coping with lengthy stressors and assisting the body in returning to normal.
Cortisol, a stress hormone, is released by the adrenal cortex. This serves various purposes, including the release of stored glucose from the liver (for energy) and the management of swelling following an injury. During this time, the immune system is weakened.

Fight or Flight Response Sympathomedullary Pathway (SAM)
The hypothalamus is also responsible for activating the adrenal medulla. The autonomic nerve system includes the adrenal medulla (ANS).

The autonomic nervous system (ANS) is a portion of the peripheral nervous system that serves as a control mechanism in the body, maintaining homeostasis. These activities are typically carried out without conscious control.

The adrenal medulla secretes adrenaline. This hormone prepares the body for a fight-or-flight reaction. Increased heart rate is one symptom of a physiological response.

Adrenaline causes sympathetic nervous system activation and parasympathetic nervous system activity to decrease.

Adrenaline causes changes in the body, such as decreased digestion, increased perspiration, and accelerated pulse and blood pressure.

Once the ‘danger’ has passed, the parasympathetic nervous system takes over and returns the body to a state of balance.

The short-term response to stress has no negative consequences and has survival benefits in an evolutionary environment.

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