Chapter 9-7

Stress and Disease Introduction

• Stress is a medical term encompassing a wide range of strong external stimuli that cause a physiologic response
• Physiologic stress necessitates cellular adaptation within the body
• Three key concepts include the stressor, its effects on the body, and the body's subsequent response

General Adaptation Syndrome (GAS) Stages

• Identified by Hans in the 1920s, GAS characterizes staged reactions to stressors
• Stage one is the alarm stage, the body reacts by releasing catecholamines like epinephrine (adrenaline), norepinephrine (noradrenaline), and dopamine
• Epinephrine acts as both a neurotransmitter in the CNS and a hormone in the blood
• Norepinephrine is primarily a neurotransmitter of the peripheral sympathetic nervous system
• Alpha receptor activation leads to vasoconstriction
• Beta receptor activation results in increased heart rate, force of contraction, and conduction velocity
• Other effects include increased respiratory rate, decreased blood flow to the skin, smooth muscle constriction, and altered liver function increasing glucose use
• This is the fight or flight response, preparing the body to deal with stress or weakening the immune system
• Stage two is resistance or adaptation. The body adapts to stressors by stimulating the adrenal gland to secrete corticosteroid hormones
• Glucocorticoids and mineralocorticoids increase blood glucose levels and maintain blood pressure
• The hypothalamus stimulates the anterior pituitary gland to release ACTH, which targets the adrenal cortex to release cortisol
• Cortisol stimulates cells to increase energy production, increase serum glucose levels, and impairs glucose use by peripheral tissues
• This decreases protein reserves and permits mobilization of fatty acids
• Cortisol reduces inflammation when it has served its purpose, helps increase red blood cell production, and affects electrolyte levels
• Endorphins reduce pain and stress while growth hormone promotes cell and tissue growth and repair, but it gets reduced during stress
• Procalcitonin levels increase more in people with ineffective coping mechanisms
• When cortisol levels are high, testosterone levels get low
• Cortisol levels and sympathetic nervous system activity return to normal during this stage
• Continued stress during this phase leads to lapses in concentration, irritability, fatigue, depression, and a depressed immune system
• Stage three is exhaustion, the adrenal glands become depleted, decreasing blood glucose levels
• Results in decreased stress tolerance, progressive mental and physical exhaustion, illness, and collapse
• The body's immune system is compromised, reducing the ability to resist disease

Effects of Chronic Stress

• The hypothalamic-pituitary-adrenal axis is a major part of the neuroendocrine system that controls reactions to stress
• It helps set off interactions among glands, hormones, and parts of the midbrain that mediate GAS
• Continued stress leads to a loss of normal control mechanisms, such as continued cortisol production, exhausting the stress mechanism and leading to fatigue and depression
• Consistently high cortisol levels suppress the immune system
• Stress and depression negatively affect the immune system, causing the body to lose its ability to fight disease
• Encourages the body to release fat and cholesterol into the bloodstream, potentially causing heart attacks or strokes
• Related conditions include depression, headaches, insomnia, ulcers, acne, diabetes, arthritis, and asthma

Coping Mechanisms

• Play a role in the physiologic response to stress
• A healthy person can manage stress with very little impact on the immune system
• A patient with ineffective coping mechanisms will have a worse effect on their immune system
• Effects are worse on a person with an already compromised immune system
• Immune suppression cannot always be corrected with psychotherapy or medication
• Positive influences help restore hope and self-esteem