General Adaption Syndrome

• Initially one becomes alarmed by a stressor that activates the hypothalamus and sympathetic nervous system
• Alarm stage
• Adaption stages
• Exhaustion stages

Alarm Stage

• (1) the alarm stage or reaction, in which the central nervous system (CNS) is aroused and the body's defenses are mobilized
• Stressor triggers the hypothalamic-pituitary-adrenal (HPA) axis
  
• Activates the sympathetic nervous system (SNS)

Adaption Stage

Resistance (adaptation) stage

• resistance or adaptation, during which mobilization contributes to “fight or flight”
• Begins with the actions of adrenal hormones
  • Cortisol, epinephrine, and norepinephrine

Exhaustion Stage

• Exhaustion stage (allostatic overload)
  Occurs only if stress continues and adaptation is not successful
• stage of exhaustion, where continuous stress causes the progressive breakdown of compensatory mechanisms (acquired adaptations) and homeostasis
• Exhaustion marks the onset of certain diseases (diseases of adaptation)
  • if stress continues and adaptation is not successful, can cause impairment of the immune response, heart failure, and kidney failure,
    leading to death.
    

Reactive, Anticipatory, and Conditional Response

Reactive response

• Involves psychologic stressors

Anticipatory response

• Anticipates a disruption in homeostasis "anticipate something bad", react to a predator or experience-dependent memory programs
• occurs when physiologic responses develop in anticipation of disruption of the optimal steady-state, also known as homeostasis

Conditional response

• Associates a stimulus with danger
• May cause posttraumatic stress disorder (PTSD) or phobias

Concepts of Stress

• Is initiated by the central nervous system and the endocrine system
• Stressor can be a perceived or real threat

Effects of Stress: Sympathetic Nervous System

• Epinephrine and norepinephrine released
• Which binds to adrenergic receptors on various cells

Causing:

• Blood pressure elevation
• Heart rate and cardiac contractility increase
• Pupil dilation
• Reduction of blood flow to skin, guts, and kidneys

Cortisol: the Stress Hormone

• Hypothalamus
  • secretes Corticotropin Releasing Factor (CRF)
    
    
• Anterior pituitary
  • secretes adrenocorticoid hormone (ACTH)
• Adrenal Cortex
  • secretes glucocorticoid: Cortisol
  • Contributes to the development of metabolic syndrome and the pathogenesis of obesity
  • Development of diabetes is secondary to cortisol-induced obesity
  • Chronic cortisol excess induces lipogenesis in the abdomen, trunk, and face, resulting in central obesity
  • Alters glucose, fat, and protein metabolism
  • Increases blood glucose levels by promoting gluconeogenesis and glycogenolysis.
  • Suppresses inflammatory and immune responses

Cortisol in the Immune System

• Systemic responses to stress may cause a decrease in innate immunity and enhance adaptive immunity
• Local responses to stress, under certain conditions, can induce proinflammatory activities
• Many immune-related conditions and diseases are associated with stress
• Stress and negative emotions increase levels of proinflammatory cytokines, providing a possible link among stress, immune function, and disease