Download Stress

Stress and Health (and the brain)
• Is stress a good thing?
Fields of interest
• Behavioral medicine
• Psychoneuroimmunology
Stress
• What is it?
– stress is the nonspecific response of the body
to any demand placed on it
• What are some of the variables that
contribute to how we respond to stress?
Psychosomatic Illnesses
• real illnesses that are exacerbated by
stress– these can be potentially life threatening
Psychosomatic Illnesses
• ulcers
• heart disease
• asthma
• various skin conditions -
(hypothalamus)
Overactivation of either system can have negative
consequences
Two systems activated during
stress and emotion
1. Sympathetic Nervous system
– activates adrenal glands to release E, NE,
and other catecholamines into blood
Are there consequences of repeated sympathetic
activation?
• perhaps………
increased
hypertension
in high stress
jobs
As a side note – sympathetic
activation is also an indicator of
arousal
• Physiological measures of arousal
• lie detector tests
– what do they measure
– problems with these tests
2. HPA Axis - (hypothalamic-pituitaryadrenal) axis
causes the release of “stress” hormones
(corticosteroids)
cortisol - in humans
corticosterone - in rats
Hypothalamus releases….
CRH – corticosterone
releasing hormone
which causes
Pituitary gland to release
ACTH – adrenocorticotrophic
hormone which causes
Adrenal Gland to release
stress hormones (cortisol
or corticosteroid)
- called glucocorticoids
negative feedback loop
glucoccorticoids in the
blood cause both
hypothalamus and
pituitary gland to
stop releasing
CRH and ACTH
Does stress have adverse
effects on the CNS?
• Sapolsky
– rats - daily injection of corticosterone
• decreased dendrites in hippocampal neurons
– vervet monkeys - 1989
• gastric ulcers, overactive adrenal gland,
degeneration and depletion of cortical neurons
Chronic stress can reduce n of cells in hippocampus
What about chronic stress in humans
and CNS?
• Cushings Syndrome – increased glucocorticoid release (can be
reversed with treatment)
• PTSD • Depressed patients
How might this happen?
• Increased cortisol or corticosterone
– increase Ca+2 influx
• increased risk of overexcitation
What can increased cortisol do?
- increase Ca+2 influx
What about stress and immune function?
A bit of background on the immune
system
• Immune system – identifies and eliminates foreign materials
that contact or enter body,
• foreign materials can be bacteria, viruses,
parasites, donated organs
– also identifies and destroys cells that have
undergone alterations (unusual rates of cell
division for example)
– immune system recognizes something on
the surface of these called antigens and
produces antibodies
How does the immune system do this?
- manufactures specialized cells (leukocytes or
white blood cells) that originate in bone
marrow and travel to other cells to mature)
• b cells - mature in bone marrow
– make antibodies that weaken or mark the antigen for
destruction by other cells
• t cells - mature in thymus
– cytotoxic t cells - can destroy target cells
– helper t cells - help immune response
• natural killer cells - destroy certain kinds of
tumors and infected cells
Can stress disrupt immune
function?
• Yes- clinical data and animal studies
• Examples:
– early Skylab astronauts • splashdown – acute stress- decreased T cells
– sleep deprivation study • kept awake 48 hrs – reduced B cell and T cell response
Can stress disrupt immune
function?
• Yes- clinical data and animal studies
• Examples:
– early Skylab astronauts • splashdown -
– sleep deprivation study • kept awake 48 hrs -
– academic exams
• medical students
Do these changes following acute
stressors impact health?
• Chronic stress situations
– examples:
Is this associated with increased
susceptibility to disease?
Chronic stress affects
immune response in
terms of illness
incidence
and recovery
Overall, 57.8% of respondents reported at least one
PTSD symptom in a 30 day period (6 - 8 weeks after
9/11)
How might chronic stress mediate these
effects on immune system?
How might chronic stress mediate these
effects on immune system?
• Increased cortisol and glucocorticoids reduce lymphocytes in blood
• increased opiate release - can reduce
lymphocytes response
• increased catecholamine release -
Role of Optimism
• Segerstrom
– law students during their first semester
Role of Optimism
• Segerstrom
– law students during their first semester
– optimism associated with
• increased n of helper T cells
• increased natural killer cell activity