HLTC22H3 Lecture Notes - Reduced Affect Display, Allostasis, Hormesis

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22 Apr 2012
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Chapter 10
Stress, Coping, and Health
• Stress is a major pathway through which psychosocial factors affect physiology and the aging process.
• Through the Neuroendocrine system, psychosocial stress can have adverse effects on the cardiovascular
and immune systems.
• Older adults may be vulnerable to the effects of physical stress
• Evidence that stress can toughen or strengthen us through heat shock proteins and social ties
• Genetic based mechanisms that protect against stress at the cellular level: DNA repair mechanisms,
antioxidants, and heat shock proteins
Stress
Three different major ways to describe stress:
1) Stress as a Physiological State
Classic Theories
• Cannon (1915) was the first physiologist to systematically describe the physiological effects of stress. He
noted that cats exposed to barking dogs would respond with a rush of epinephrine or adrenaline into their
systems. Stress activates the hypothalamus which readies organism for fight or flight
• (SNS)- reacts to stress in two ways
1) Originates in the spinal column (preganglionic nerves- secrete acetylecholine) and radiate to the target organs
(postganglionic nerves- use norephinephrine)
2)In sympathetic/adrenal medulla (SAM)- nerves radiate to adrenal medulla- which secretes epinephrine
(adrenaline) and norepinephrine (noadrenaline) into blood [stimulates organ muscles and blood vessels]
• Epinephrine- increases metabolic rate, more powerful
• Norepinephrine- stimulates the peripheral vascular system & raises blood pressure
• Sympathetic activation- can cause piloerection response
• PNS- brings the body back to homeostasis after stress
- Over activation of SNS can result state of shock
- Can cause blood level to get so low that cardiac arrest occurs
- Porcine stress syndrome: pigs die simply from stress of being transported
- Prolonged increases in blood pressure and blood clotting would eventually result in hypertension and
cardiovascular disease
SELYE = 1) Hypothalamus secrets corticotrophin-releasing hormone (CHA) activates pituatary which
activates ACTH -> which activates corticosteroids such as = glucocorticoids and mineral corticoids
- Pituitary releases adrenocorticotropin hormone (ACTH) into blood stream
- Cannon = fight/flight reaction, could have very harmful effects if prolonged.
- Glucocorticoids are fat-soluble molecules, which enables them to cross cell membranes in every organ system
- 2) dualistic processes 1) ALARM (fight/flight) 2) ADAPTATION (use to stressor) 3) EXHAUSTION (tired,
- Modern Theories
- Both Cannon and Seyle argued that there are general responses to stress, but it is now widely recognized that
there are individual differences in stress reactions.
- From a psychosocial perspective, studies investigating the effect of stress on sympathetic arousal, including
heart rate, respiratory rate, and galvanic skin response (a measure of the degree to which the electrical
conductance of the skin is affected by sweating) consistently found individual differences in the patterning of
sympathetic arousal.
- • In addition, it is now recognized that activation of the HPA axis is an attempt to buffer the rather damaging
influence of prolonged SNS activation.
- SNS activates immune system responses, encouraging inflammation; HPA (slower change) activation
suppresses the immune/inflammatory response
• In addition, we now know that most, if not all, of the endocrine hormones are affected by stress, increasing or
decreasing in fairly complex temporal patterns.
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• In general, stress activates those hormones that increase metabolic functioning and suppresses those involved
in long-term growth and maintenance.
• The recognition of broader endocrine responses to stress has led to an argument for a third stress pathway,
through oxytocin.
TAYLOR Oxytocin is a hormone that is very important in reproductive activities such as breast-feeding.
MEN- alone, women company
Taylor’s observation= fight/flight and affliate respone
Stress and the Development of Chronic Illness
• Stress can results in heart disease and cancer
• Risk factors: blood pressure, cholesterol, atherosclerotic, and arteriosclerotic process, and immune
functioning, promote tumor proliferation, suppress natural killer (NK) cells
Overall relationship b.w stress and cancer is weak in humans
MCEWAN
• Allostasis- fluctuation in physiological systems to meet external demands
• Allostatic load- the physiological costs of chronic exposure to fluctuating or heightened neural or
neuroendocrine responses that result from repeated chronic environmental challenges
Models posit cascade effects of stress on cardiovascular, neruroendocrine, and metabolic systems
Positive Physiological Changes
Infants exposed to stress had better overall health, did things quicker
Adults tend to be taller in cultures (circumcision, sleeping apart from parents, sacrification, early puberty
Regular exposure to challenges and stressors followed by adequate recovery periods can cause peripheral and
central physiological changes that increase one’s future capacity for more positive forms of arousal and the
suppression of more costly forms of arousal.
Stroking and touching can stimulate growth hormone
• Basically, it has been argued that SAM activation (sympatho-adrenal-medullary) activation is associated with
better performance on cognitive and physical tasks, as well as emotional stability, whereas HPA axis (the
hypothalamic-pituitary-adrenal) axis arousal is less beneficial and may interfere with performance.
• Hormesis- low levels of exposure to a stressor can result in resistance to more lethal levels
moderate exposure to toxins can result in increased resiliency to stress on a number of different levels- perhaps
greater longevity
Physiological Stress and Aging
• The optimal stress response is a sharp increase in cortisol
- In aging rats the cortisol is much slowly released, and longer to return to baseline
- Too much epinephrine can cause microtears in blood vessels-
- Too much cortisol damages the hippocampus
- In humans, the findings on age-related changes in the stress response are quite variable and somewhat
contradictory.
- Older adults do not necessarily show increased cortisol responses to psychological stress, however, and
there are some suggestions that there may be gender differences.
- Young men and older women showed increase cortisol release with cognitive testing
- Sedentary middle aged men are vulnerable to heart attacks with sudden strenous activity
- Elders vulnerable to HEAT and COLD stess.
CHARACTERISTICS OF THE ENVIRONMENT
Trauma
Traumatic stress : direct personal experience of an event that involves serious threat to the life or physical
integrity of self or significant others, or simply learning about such an event of the same peeps
• Traumatic stress generally evokes feelings of extreme terror and helplessness, followed by emotional
numbness.
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