Physiology of Chronic Stress Flashcards
What is stress?
It isn’t an event that happens.
It is a cognitive appraisal of experiences that lead to activation of physiological mechanisms including the HPA axis. It also leads you to react in a specific way.
It is an INDIVIDUAL phenomenon.
What can chronic stress cause?
Dysregulation of physiological stress mechanisms - including dysregulation of the HPA axis.
How does the HPA link with psychiatric disorders?
Dysregulation of the HPA axis has been shown to be linked to a proportion of Ps who also suffer with a psychiatric disorder, inc high levels of cortisol in these Ps.
How can stress affect children?
Children who experience adverse hardship in their formative years may later display evidence of HPA dysfunction.
Does HPA dysfunction go away immediately after the removal of stressors?
No - HPA axis dysfunction many linger after removal of stressors = long-term risk for health.
What do we mean when we say stress is an individual experience?
Different Ps will interpret different events in different ways - is no uniform approach to a stressor.
What one P may find stressful, another may not. It can be real, imagined, internal or external.
How do we quantify stress?
Difficult to do - however Holmes & Rahe Stress Scale quantified life events aiming to identify which Ps would be predisposed to stress-related illness depending on what events they were experiencing.
What is the Holmes and Rahe Stress Scale based upon?
The belief that significant life events which are associated with change are stressful events in a person’s life - and these can be quantified.
What is the criticism of the Holmes and Rahe Stress scale?
It assumes homogeneity - that all Ps react to the same events in the same way. Rather than appreciating the individual nature that Ps respond to stress and what they determine as stressful.
Is reductionist.
What time period does the Holmes and Rahe Stress Scale look at?
The amount of stressful events in the past 12 months.
What are the three subtypes of stress?
Postive stress
Tolerable stress
Toxic stress
Which type of stress is this?
- Unbuffered adverse effects of great duration & magnitude
- Maladaptive / poor coping & compromised recovery
- Inc lifelong risk for physical & mental disorders
- Compromised brain architecture
- Dysregulated physiological systems
Toxic stress
Which type of stress is this?
- A personal challenge with satisfying outcome
- Sense of mastery and control
- Healthy brain architecture
- Good self esteem, judgement & impulse control
Positive stress
Which type of stress is this?
- Adverse life events buffered by supportive relationships
- Coping and recovery
- Healthy brain architecture
= Good self esteem, judgment & impulse control
Tolerable stress
What is another name for positive stress?
Eustress
What leads Ps to determine an event as toxic stress?
Ps that dont have the resources to manage with the stressor, or their coping mechanisms make the problem worse. Leads to compromised brain architecture.
What determines whether an adverse event will be stressful or not to a person?
Whether they have adequate internal and/or social resources to manage the event.
How does stress in today’s society compare to historical threats?
Historical threats - more short-term stresses. Today - modern life is more likely to provide persistent & chronic stressors.
What happens if there is an aberration of the stress system?
Can develop health conditions - psychiatric or somatic
What is the acute stress response?
Adrenal medulla produces adrenaline & noradrenaline =
- Inc HR
- Inc BP
- Inc RR
- Inc bronchial dilation
- Inc pupil diameter
- Dec GI activity
Does the acute stress response resolve slowly or quickly? How does it resolve?
Resolves quickly - due to negative feedback loop
What is the mammalian “stress-axis”?
The HPA Axis
What are the core components of the HPA axis?
Hypothalamus
Pituitary gland
Adrenal glands
What does the HPA axis influence?
Stress responses
Immune functions
Mood & emotional states
How is the HPA axis terminated?
Via negative feedback loop - the adrenal medulla produces cortisol (as glucocorticoids) which inhibits the hypothalamus and pituitary gland from producing more hormones.
What do high levels of cortisol do to the immune function of the body?
High cortisol suppresses immune function
Which hormones do the following produce as part of the HPA Axis?
- Hypothalamus
- Pituitary gland
- Adrenal glands
Hypothalamus = Corticotrophin Releasing Hormone (CRH)
Pituitary gland = Adrenocorticotrophic Hormone (ACTH)
Adrenal glands = Cortisol (as glucocorticoids)
Which part of the pituitary gland produces ACTH?
Anterior pituitary
Which part of the adrenal glands produces cortisol?
Acute stress = Adrenal medulla
Chronic stress = Adrenal cortex
How long a period does the HPA axis work over?
24 hour period.
When are cortisol levels low?
At nighttime
Which hormone is produced in high quantities at night?
Melatonin
When does the cortisol awakening response occur?
About 90 minutes after awakening.
When are cortisol levels high?
During the day
How is the HPA axis linked to depression?
Some depressed Ps have dysregulated HPA axis = high levels of cortisol at all times.
When the HPA axis is performing normally - what does it do? What does negative feedback of this system prevent?
Normally - maintains homeostasis and wellness of the body - allows us to fight germs off during the day.
Negative feedback - prevents allostatic overload
What does exposure to chronic stress do to the HPA axis?
Causes allostatic overload - leads to dysfunction of the HPA axis.
Once a chronic stressor has been removed, does the HPA axis automatically return to normal?
No - the HPA axis can remain dysfunctional for a period of time afterwards.
What is the term for adaptive physiological changes due to activation of homeostatic mechanisms in response to the changing environment?
Allostasis
What are the clinical signs of allostatic overload?
Elevated catecholamine levels
HPA dysfunction
Raised cytokine levels (IL1, IL6 & TNF)
How can the immune system communicate with the HPA axis?
Via production of cytokines
What is an ACE?
Adverse Childhood Experience
How do ACEs interplay with the HPA?
ACEs = increase allostatic overload in later life –> increase in physical and psychiatric conditions
What are ACEs likely to present as in adulthood?
Poverty
Substance misuse / abuse
Affective & anxiety disorders
Which part of the brain is involved in learning and memory?
Hippocampus
What does damage to the hippocampus result in?
Cognitive impairment + inability to learn new information
How do ACEs affect the hippocampus?
Is a link between ACEs and reduced hippocampal volume - can cause associated memory problems.
How do high levels of cortisol affect memory?
Can impair ability to encode/recall information
How do high levels of cortisol affect immune function?
Can suppress immune function
How do high levels of cortisol affect inflammation?
Can increase inflammation?
How do high levels of cortisol affect sleep?
Can reduce the amount of REM sleep
How do high levels of cortisol affect the hippocampus?
Can reduce the amount of dentate gyrus neurogenesis in the hippocampus
What impacts do high cortisol levels have in an expectant mother?
Can cross the placenta - babies are found to have higher levels of cortisol themselves, even a significant time after birth.
Also linked to low birth weight & preterm delivery
