When stress hits, your body kicks into high gear. The stress response activates your nervous system and hormones, preparing you to fight or flee. This survival mechanism affects everything from your heart rate to your immune system.

Chronic stress can wreak havoc on your health. It messes with your cardiovascular, immune, digestive, and reproductive systems. Your brain takes a hit too, impacting memory and mood. Understanding stress helps you manage its effects and stay healthy.

Stress and its effects

Definition and types of stressors

• Stress is the body's response to any demand or threat, whether real or perceived, that requires an adjustment or response
• Stressors can be physical (injury, illness), psychological (anxiety, fear), or environmental (noise, crowding)

Physiological and psychological effects of stress

• The stress response involves the activation of the sympathetic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis
• Physiological effects of stress include increased heart rate, blood pressure, respiration, and blood glucose levels, as well as suppression of the immune system and digestive processes
• Psychological effects of stress can include anxiety, irritability, depression, and cognitive impairments such as difficulty concentrating and memory problems (forgetfulness, mental fog)

Hypothalamic-pituitary-adrenal axis

Components and functions of the HPA axis

• The hypothalamic-pituitary-adrenal (HPA) axis is a neuroendocrine system that plays a central role in the body's stress response
• The hypothalamus secretes corticotropin-releasing hormone (CRH), which stimulates the anterior pituitary gland to release adrenocorticotropic hormone (ACTH)
• ACTH stimulates the adrenal cortex to secrete glucocorticoids, primarily cortisol, which have widespread effects on various organ systems
• Cortisol mobilizes energy stores, increases blood glucose levels, suppresses the immune system, and modulates brain function and behavior

Regulation of the HPA axis

• The HPA axis is regulated by a negative feedback loop, where elevated cortisol levels inhibit further release of CRH and ACTH
• This negative feedback mechanism helps to maintain homeostasis and prevent excessive or prolonged activation of the stress response
• Dysregulation of the HPA axis, such as in chronic stress or certain disorders (Cushing's syndrome), can lead to persistently elevated cortisol levels and associated health problems

Allostasis and stress adaptation

Concept of allostasis and homeostasis

• Allostasis refers to the process by which the body maintains stability (homeostasis) through physiological or behavioral change in response to stressors
• Allostatic systems, such as the HPA axis, autonomic nervous system, and immune system, work together to adapt to challenges and restore homeostasis
• Allostasis allows the body to maintain stability in the face of changing demands, while homeostasis refers to the maintenance of a relatively constant internal environment

Allostatic load and overload

• Allostatic load refers to the cumulative wear and tear on the body resulting from repeated or chronic stress and the inefficient operation of allostatic systems
• Allostatic overload occurs when the demands placed on the body exceed its capacity to maintain homeostasis, leading to dysregulation of allostatic systems and increased risk of disease
• Factors contributing to allostatic overload include prolonged or repeated exposure to stressors, lack of adaptation or habituation to stressors, and individual differences in stress vulnerability (genetic predisposition, early life experiences)

Chronic stress consequences

Cardiovascular and immune systems

• Chronic stress can contribute to hypertension, atherosclerosis, and increased risk of heart attack and stroke by promoting inflammation, endothelial dysfunction, and unhealthy behaviors (smoking, overeating)
• Prolonged stress can suppress immune function, increasing susceptibility to infections (common cold, influenza) and autoimmune disorders (rheumatoid arthritis, multiple sclerosis)

Digestive, reproductive, and nervous systems

• Stress can exacerbate gastrointestinal disorders such as irritable bowel syndrome (IBS), ulcerative colitis, and peptic ulcers by altering gut motility, permeability, and microbiome composition
• Chronic stress can disrupt the hypothalamic-pituitary-gonadal (HPG) axis, leading to menstrual irregularities, reduced fertility, and sexual dysfunction (erectile dysfunction, decreased libido)
• Sustained stress can cause structural and functional changes in the brain, affecting memory, learning, and emotional regulation, and increasing the risk of mental health disorders such as depression and anxiety