In physiology, stress is the body's reaction to internal or external disruptions that throw its balance (homeostasis) off. These disruptions, called stressors, can range from illness and injury to sleep deprivation and nutritional deficiencies. The body activates specific pathways to handle this stress, impacting overall health and well-being. [3, 4, 5, 6]
Types of Stressors and Their Impact
Stressors can be categorized as either physical or psychological:
- Physical Stressors: These include illness, injury, intense exercise, extreme temperatures, and nutritional deficiencies. The body responds physiologically to combat these threats. For example, illness triggers inflammatory responses, while intense exercise leads to increased heart rate and respiration.
- Psychological Stressors: These involve mental or emotional challenges like work deadlines, relationship problems, or traumatic experiences. These stressors still elicit a physiological response, even though the initial trigger isn't directly physical. The release of hormones like cortisol plays a crucial role in this response. [5, 7]
The Physiological Stress Response
When faced with a stressor, the body initiates a cascade of events designed to restore homeostasis. This often involves the release of stress hormones, like cortisol and epinephrine (adrenaline). [7, 8] These hormones trigger various changes throughout the body, including:
- Increased heart rate and blood pressure: This prepares the body for "fight or flight." [7]
- Elevated blood sugar: Providing readily available energy.
- Suppression of the immune system (in prolonged stress): Chronic stress can weaken the body's defenses. [7]
The intensity and duration of the stress response depend on the severity and duration of the stressor. Acute stress is a short-term response, allowing the body to manage immediate threats. Chronic stress, however, can have detrimental long-term effects on physical and mental health. [7] For example, prolonged exposure to elevated cortisol levels is linked to various health issues, including cardiovascular disease. [7]
Examples of Stress in Physiology:
- Exercise: Intense physical activity is a physiological stressor that leads to changes in heart rate, respiration, and muscle metabolism.
- Infection: The body’s immune response to infection is a stress response designed to eliminate pathogens.
- Trauma: Physical trauma leads to the release of stress hormones and the activation of pain pathways.
- Mental stress: Worry, anxiety, or grief can elevate cortisol levels and impact various physiological systems.
Scientific Understanding: Studies examining the neuronal responses to physiological stress illustrate its complex effects on the body's regulatory systems. [2] Research also highlights that measuring stress hormones (like corticosterone in birds) can provide valuable insights into an organism’s integrated stress response over time. [9] The interplay between stress and behavior (like "boldness" in animals) is another area of ongoing research. [10]
