ICL 6.0: Stress Flashcards
what is the stress theory?
adaptation aka maintaining an internal environment, is the essential process of life
adaptation occurs at all levels of life (cellular through organism)
the human adaptive system is a complex interconnection of organ systems maintaining organism integrity and adapt to the external environment
the adaptive processes can become maladaptive = STRESS –> maladaptation of the adaptive process results in organismic distress, strain, and disease
the primary organ of adaptation is the BRAIN
what is the primary organ of adaptation?
the brain!
the CNS and its extensions and key to the adaptive process associated with stress theory
why is stress theory important?
genetics and the interaction of the person’s constitution with the environmental aspects of life and the stress responses that occur are what lead to depression, anxiety, schizophrenia, etc.
mental Illness models often use the Stress-Diathesis concept to explain etiology of mental illness –> this stress theory provides a dynamic model that informs how to treat the illness effectively and provides a model that informs the provision of health care services across the spectrum of diseases and across the life cycle
so we look at the environments that we’re providing healthcare in, what are we addressing in the person’s psychosocial or physical environment to elevate and minimize the effects of stress on a person
how is organ function controlled by the brain?
vital organs have intrinsic controls and ANS ganglionic reflex loops that maintain operation under limited demand
rapid changes in demand require higher brain centers to activate, regulate and coordinate organ responses
the stress response involves the systems maintaining organism integrity (homeostatic controls) –> these include the ANS, neuroendocrine system, and the endocrine system
what is the pivotal organ involved in the fight-or-flight response?
adrenal medulla pf the adrenal gland
during sympathetic activation, there is NE and epinephrine (80%) release
when the sympathetic nervous system has outflow in the stress response, that direct innervation is happening extremely rapidly in all the organs that it stimulates
however, then when the neuroendocrine response via the adrenal medulla maintains this sympathetic response, the effect is functionally identical to direct sympathetic innervation but there is a 20-30 second delay in onset then a 10x increase in effect duration
what is the chain of structures involved in the neuroendocrine sympathetic response?
central amygdala –> lateral hypothalamus –> sympathetic nerves –> adrenal medulla –> epinephrine –> increased HR, blood flow to muscles, breakdown of glycogen and airflow to lungs
what are the effects of adrenal medullary stimulation?
this is the neuroendocrine response:
Increased arterial blood pressure
Increased blood supply to the brain
Increased heart rate and cardiac output
Increased stimulation of skeletal muscles
Increased plasma free fatty acids, tryglycerides, cholesterol
Increase release of endogenous opioids
Decreased blood flow to kidneys
Decreased blood flow to GI system
Decreased blood flow to skin
what is the HPA axis?
release of cortisol via the hypothalamic pituitary adrenal axis as a response to stress!
corticotrophin releasing factor (CRF) is released through the hypothalamic-hypophyseal portal system from the hypothalamus to the anterior pituitary
this stimulates the release of ACTH from the anterior pituitary into the circulation which then triggers the release of cortisol and corticosterone from the adrenal cortex
cortisol then has a negative feedback on the anterior pituitary and hypothalamus to inhibit the release of too much cortisol
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what is the normal rhythm of cortisol release in the body?
cortisol has a diurnal rhythm aka a daily rhythm where it tends to peak around 4 in the morning and then it has a slow decline throughout the day
this operates separately from the pulsing that occurs with a stress response
what are the effects of cortisol/glucocorticoid hormones?
- increased glucose production
- increased urea production
- increased release of free fatty acids into systemic circulation
- suppression of immune mechanisms
- increased ketone body production
- enhancement of catecholamine synthesis in the adrenal medula
- inhibition of inflammation
so the effects of cortisol are in some ways providing a lot of energy for the body to utilize during a stress response but the inhibition of inflammation and the suppression of the immune system are more designed as a protection for the body while it’s in the stress response from being overwhelmed by immune mechanisms and being able to flee effectively; you’ll experience the inflammation later
how does stress effect the immune system?
stress inhibits inflammation and suppresses immune mechanisms
the immune system can signal the CNS with cytokines through multiple pathways –> cytokines are small secreted proteins which mediate and regulate immunity
one pathway that the CNS regulates the immune system through is the the pituitary-adrenocortical axis (HPA)
cortisol can facilitate and inhibit immune function –> lower levels facilitate the immune system while higher stress levels of cortisol inhibit
immune cells have receptors for epinephrine –> stress related secretion of epinephrine can enhance and/or inhibit immune function = very complex interaction
organs of the immune system are innervated by both branches of the ANS; both the sympathetic and parasympathetic
what are the 2 main models of the stress response?
- psychological appraisal and response model of stress
- neurological block model of CNS areas involved in appraisal and response
so we’re going to be look at how does the stress experience happen and how is it triggered by psychological factors and what are the brain areas associated with that –> the implication is that how we perceive an event really drives our stress response, it’s not just about the event itself
what is the psychological appraisal and response model of stress?
appraisal processes are key to whether or not there is some kind of stress response
the appraisal processes are divided into primary and secondary
the role of the appraisal processes is to both determine whether an experience/event has a threat potential and whether or not the organism has the resources to cope with that threat potential
Lazarus said that the primary decision about whether something is a threat happens very quickly and is based on our beliefs and commitments in life –> beliefs and commitments can be divided into things that are conscious and unconscious that occurred early in life
if our primary belief system determines that something is a not a threat or challenge we ignore it and stress won’t occur; but if we do determine it’s a threat or challenge, we move on to secondary processing and what our mind does it look at resources, options and the effectiveness of being able to deal with the stressor which will lead to some kind of coping behavior
a coping behavior can be a behavioral or psychological response –> your behavioral and psychological responses then cause biological responses that will then go impact the primary decisions; so if your psycholiglca and behavioral responses are good and work to calm you down then your biological responses will also do the same and that will go back and tell your primary process that you can handle this stressor
what is the neurological block model of CNS areas involved in appraisal and response during stress?
- the whole process of taking in the stress happens in the association areas, prefrontal cortex and hippocampus
- then emotions are generated based on your appraisal of the stress in the prefrontal-amygdala and insula-hippocampus connections
- these emotions then send feedback to the cortex and limbic system via the brainstem aminergic nuclei such as the locus ceruleus, raphe nuclei, and ventral segmental nucleus which release NE, serotonin, and dopamine
the emotions also initiate autonomic and endocrine response in the hypothalamus and paraventricular nucleus
- this activation of the autonomic system drive the stress response which involves the nucleus of the solitary tract, intermediolateral cell column, pituitary gland and adrenal gland like we talked about earlier
how do we measure stress?
- the life events-Holmes scale and the Rahe-social readjustment rating scale
- Hassles and Uplifts scale
what is the life events-Holmes scale and the Rahe-social readjustment rating scale?
43 items on the scale-each life event has a relative number of stress units assigned – list each item that has occurred in the last 12 months
can include death of a spouse, divorce, marital separation, jail, death of a family member, personal injury or illness, marriage, fired at work, retirement
this gives a quantitative index of stress following a situation requiring adjustment
how does age, sex, marital status and social class effect people’s life events-Holmes scale and the Rahe-social readjustment rating scale stress score?
there is significant variability that exists among groups in the perception of life events and the frequency of events
- age: younger people have more life events than older but the ones that older people face are worse
- sex: women tend to have greater life event scores than men
- marital status: single, separated and divorced people accumulate a larger number of events
- social class: inconsistent relationship with life events
what is the Hassles and Uplifts stress scale?
there’s 117 hassles and 135 uplifts that assess the daily and cumulative impact of everyday demands
Hassles scale was found to be a better predictor of subsequent and concurrent psychological symptoms than the life events scale – probably because it’s measuring immediate things/events; it’s not going to tell you an accumulated score
what are the physiological changes seen with stress?
- cortisol
- heart rate
- catecholamines
- immune suppression
it can be any biological endpoint of the stress response system!
however, physiological measures are complicated by inter-subject variability or intra-subject variability due to diurnal variations or situational factors
what are the neurological changes seen with stress?
EEG or FMRI of brain activity shows changes during stressor or recovery from stressor period
what can plasma cortisol tell you?
it indicates the dynamic state of the negative feedback loop in the cortisol regulation
researchers looked at the variability in plasma cortisol while people were in a float tank vs. not – mean levels and the variability of cortisol decreased (:
what is Selyes Gas’s model of stress and illness?
the general adaptation syndrome which is divided into 3 phases:
- alarm
- resistance
- exhaustion
he said the exhaustion phase was what was primarily connected to the illness situations
what happens during the alarm phase of Selyes Gas’s model of stress and illness?
- enlargement of adrenal cortex
- enlargement of lymphatic system
- increase in hormone levels
- response to a specific stressor
- epinephrine release associated with high levels of physiological arousal and negative affect
- heightened susceptibility to illness
if the stress is prolonged, slower components of GAS are set into motion with stage II
what happens during the resistance phase of Selyes Gas’s model of stress and illness?
- shrinkage of adrenal cortex
- lymph nodes closer to normal size
- hormone levels sustained
- physiological arousal stays high, but parasympathetic branch of the ANS counteracts
- individual under resistance can endure the stressor and resist further debilitating effects from the stressor
- heightened sensitivity to stress
if stress continues at intense levels, hormone reserves are depleted, fatigue sets in and you move into stage III
what happens during the exhaustion phase of Selyes Gas’s model of stress and illness?
- dnlargement /dysfunction of lymphatic structures
- increase in hormone levels
depletion of adaptive hormones - decreased ability to resist either the original or extraneous stressors
- affective experience which is often depression
what is homeostasis?
describes mechanisms that hold constant a controlled variable by sensing its deviation from a “setpoint” and feeding back to correct the error
emphasis is on steady state and optimal set points
what is allostasis?
mechanisms that change the controlled variable by predicting what level will be needed and overriding local feedback to meet anticipated demand
emphasis is on optimal operating ranges of physiological systems, setpoints based on system prediction of demand
this is the stress response!!
what is the homeostasis vs. allostasis stress model?
Peter Sterling and Joseph Eyer
in allostasis, prior knowledge leads to a prediction of the demand which effects the control system of homeostasis – homeostasis is the control system without any prior knowledge
our brain has the ability to override set points that are normally driven by more biological mechanisms –> for example, your BP set point is pre-set by certain biological factors but if you have stress responses in the environment, it could override the biological set point and drive the BP higher
allostasis and allostatic load provide a dynamic model of adaptation leading to maladaptation resulting in organismic distress that can be applied to both physical and mental illness
what is allostatic load?
McEwen said that the allostatic load represents the cumulative, multi-system view of physiological toll that may be exacted on the body through attempts at adaptation
so if you have an allostatic system trying to respond to an external threat and it’s raised the BP and keeps it there for a period of time, this creates an allostatic load! it’s a physiological toll from trying to maintain that BP high
if allostasis keeps occurring over and over in ways that become dysfunction, you end up with allostatic load instead of adaptation
what is allostatic overload?
when the allostatic load continues for long periods becoming independent of original adaptation effort
what 4 mechanisms could result in allostatic load?
- repeated hits
- lack of adaptation to the same stressor
- prolonged response without recovery = failure to shut off either the hormonal stress response or to display the normal trough of the diurnal cortisol pattern
- inadequate response; physiological response promote stress responding/adaptation but they also have protective mechanisms! inadequate hormonal stress response which allows other systems, such as the inflammatory cytokines, to become overactive
normally there’s an increase of stress and an increase in physiologic response but then you deal with it and the physiological response goes down
higher allostatic load scores are associated with what?
- poorer cognitive and physical functioning
- predicted larger decrements in cognitive and physical functioning
- associated with an increased risk for the incidence of cardiovascular disease, independent of sociodemographic and health status risk factors
higher baseline allostatic load scores are associated with what?
- significantly increased risk for 7 year mortality
2. declines in cognitive and physical functioning
how is the concept of allostatic load associated with mood disorders?
allostatic states leading to allostatic load produce cumulative changes in both brain and body
- amygdala hyperactivity
- HPA dysregulation which results from disruption of normal sleep patterns
- delayed atrophy of hippocampus and prefrontal cortex from high levels of cortisol –> the hippocampus is the key in shutting off the HPA axis after psychological stressors
- abdominal obesity and bone mineral loss
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