Autonomic Nervous System 2 Flashcards
What is stress and stress response?
Stress: Any challenge to the integrity or survival of the organism. It includes the complex interaction of biological, behavioral, cognitive, sociocultural, and environmental changes that can disrupt genetically predisposed homeostasis.
Stress Response: An array of mechanisms designed to
defensive and adaptive
restore homeostasis.
Describe the hypothalamic pituitary adrenal axis
Hypothalamus releases corticotropin-releasing hormone (CRH or CRF), which stimulates the anterior pituitary
- Anterior pituitary releases adrenocorticotropic hormone (ACTH), which stimulates adrenal cortex
- Adrenal cortex produces glucocorticoids (especially ‘stress hormone’ cortisol)
- Cortisol completes negative feedback loop by inhibiting CRH and ACTH release
Describe the physiological stress response
• Emotional and physical stressors activate the
sympathetic nervous
system and HPA
• Short term reaction(acute stress ) leads to ‘fight or flight
’ response
• Long-term or chronic stress is problematic because many of the acute stress responses are harmful if sustained
How do the EPI and NE react in the stress response?
• NE from sympathetic post- ganglionic terminals normally acts locally like a neurotransmitter
• Medullary chromaffin cells
release (≈ 4:1 ratio) into bloodstream
• Effects throughout the body, more like a hormone
→ “neuro-hormone”
What is the fight or flight response?
• First described by Walter Cannon, 1920s
• Hyperarousal when organism is threatened: Resources are
mobilized
• Amygdala→HPA axis activation
• Cardiovascular: Increased blood pressure (BP), heart rate, stroke
volume and contractility to improve muscular blood supply
- Lungs: Bronchodilation and increased breathing
- Skin: vasoconstriction to raise BP, anticipatory sweating to counteract thermogenesis (hence the typical cold, clammy skin)
- Energy mobilization: Increased blood glucose and fatty acids
- In milder form, part of arousal and stress response
Contrast acute and chronic stress
- Acute stress is short-term with a clearly defined beginning and end
- Chronic stress is long-term with no clear end
• Both acute and chronic stress trigger the physiological
stress response and adaptation
• Prolonged stress can lead to exhaustion and immunocompromise
Describe the Dysregulation of HPA
Abnormal cortisol levels found - in:
– Anxiety disorders (high - cortisol)
– Depression (high cortisol)
– PTSD (high and low cortisol)
– History of child abuse (high cortisol)
– Professional burnout (high cortisol)
Give stress and health examples
- In patients with coronary artery disease, , risks of acute in the short period after an anger myocardial infarction in the short period after an outburst is doubled
- In the months after the death of a spouse, mortality from all causes is increased.
- Rate of defibrillator firings increased 3X in the month following the World Trade Center attack in NYC.
- Chronic work-related stress 2X – 3X risks of cardiac events, especially when employees perceive little control over their work environment.
What is the genetic contribution to stress?
Genetics (Nature)
– Genotypic variations in HPA afferents are associated with specific personality types and regulate HPA response to psychological and physiological stressors
- Shorter form of the serotonin
is associated with increased stress response and
vulnerability to depression and alcoholism
What are the nurture factors of stress?
Early life experience factors (Nurture)
– Early experiences can “hard-wire” the stress-response (i.e., modeling, secure attachment)
– Greatest learning occurs in first 9 months
– Early trauma/abuse (risk factor)
– Uncertainty in food supply (risk factor)
transporter
— Novelty/enriched environment
(protective factor)
What are the components of the. Acute stress response?
- Mobilization energy at cost of energy storage
- Increased cardiovasc. and cardiopulm. tone
- Suppression of digestion
- Suppression of growth
- Suppression of reproduction
- Suppressed immunity/inflammatory response
- Altered plasticity, structure in brain structures
- Alterations in neural processing, thresholds
- Increased alertness
What are the pathological consequences of prolonged stress?
- Fatigue, muscle wasting, insulin resistance
- Hypertension
- Ulcers
- Psychogenic dwarfism
- Suppression of ovulation, impotency, loss of libido
- Impaired disease resistance
- Accelerated neural degeneration
- Impaired cognition
- Exhaustion and reduced sleep
How does stress effect the immune system?
Acute stress (injury) —> immune system
Chronic stress—> increased cortisol production impairs production of natural killers, T cells, B cells and antibodies —> which. Suppresses immune system
How does stress affect metabolic disorders?
Chronic stress—> increased glucose and fat in the bloodstrea. Decreased oxygen flow and organ efficiency—> impair cellular response to insulin —> chronic stress Induced hyperinsulinemia—> type 2 diabetes, coronary artery disease, and metabolic syndrome
Note: In older adults, chronic stress is more highly associated with with elevated insulin levels than than with any other physiologic measure
What is the immune paradox of chronic stress?
• Acute stress the immune system (e.g., injury)
• Chronic stress is associated with immunosuppression
– Excess glucocorticoids in blood of natural
killer cells – Reduced antibodies
• Paradoxically, chronic stress can also lead to heightened autoimmune response (body attacks itself): MS, RA, juvenile diabetes, allergies
