week 9 part 1 Flashcards
What does stress have an impact on?
- Mood disorder
2. Mental disorder
What are the neuroendocrine response to stress?
- Cognitive identification of stimulus
- Appraisal of capacity to respond
- Physiological response
- Behavioural response
- Recovery
What is stress?
A learned response in majority of the cases
What can stress also be?
Autonomic sensor response to an environment that is noxious/ damaging to the organism
What is the cognitive identification of stimulus seen as ?
- Stressful
2. harmful
What are examples of physiological response?
- Increase heart rate
- Respiration
- Vasoconstriction
- Suppression of immune and reproductive system
- Redirection of glucose metabolism
What is behavioural response?
e.g. fight or flight
What is recovery?
Return to homeostasis
How do these physiological responses occur?
- Very rapidly
2. Bypasses cognitive identification in certain circumstances
When does stress occur?
Arousal
What will arousal evoke?
The stress response of predator
What is not always negative?
The psychological stress
What involves the activation of almost all nervous system?
- The physiological healthy stress response
2. The maladaptive stress response
What happens when the organism is recognising the stressor?
It’s engaging the central nervous system
When is the thermoreceptor in the skin sending information to the spinal cord?
When an organism is in the presnece of strong level of pollution or elevated heat
What occurs when the brain is engaged in the stress response?
It will send signals via the peripheral nervous system e.g. ANS or SNS
What is the consequence of ANS becoming activated by stress?
- More muscles become activated by stress
2. Voluntary muscles become innervated
What will the sympathetic nervous system be mobilising?
The resources of glucose in your cells and start changing the metabolism of fat and protein and turning it into sugar
What systems will shut down as a response to stress response?
- Immune systems
2. Reproductive systems
What does stress involve?
Main centre of sensation gathering
sensation relay of the brain
Where does the stress response start?
Hypothalamus
- send hormone signals to other parts of the brain to trigger physiological stress response
What is the mechanism of hypothalamus?
- Hypothalamus releases hormone into pituitary gland
- Releases hormone
- Reaches the circulation
- Reach top of kidney into adrenal gland
- Release glucorticoid (cortisol)
What does hypothalamus take on?
- Visual Information
- Auditory Information
- Takes information from nerve endingsand receptor son skin
What is released at the level of hypothalamus?
Release of CRH
What will CRH stimulate?
The release of ACTH fin the pituitary gland
Where will ACTH reach?
The bloodstream into adrenal gland and produce the release of glucorticoid
What is the limbic system?
complex set of structures that lies on both side of the thalamus, just under the cerebrum
series of cortical structures surrounding the limit between the cerebral hemispheres and the brainstem
What does the limbic system include?
- Hypothalamus
- Hippocampus
- Amygdala
- Other several other nearby areas
What is the role of limbic system?
- primarily responsible for our emotional life
2. Formation of memories
What is the integrator of stress response?
Amygdala
What is the limbic system seen as ?
Primitive evolutionary parts of the brain
How does the limbic system operate by?
Influencing the endocrine system and the autonomic nervous system
What are the adrenal glands?
Small glands located on top of each kidney
Endocrine gland that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol
What is the adrenal cortex?
- Outermost layer of the adrenal gland
2. Within the cortex 3 layers called zones
What are the adrenal cortex devoted to produce?
hormones
- Aldosterone
- Cortisol
- Androgens
Where is adrenal medulla located?
centre of each adrenal gland
surrounded by adrenal cortex
What is the chromaffin cells a main source of?
catecholamines adrenaline and noradrenaline, released by the medulla
Approximately 20% noradrenaline (norepinephrine) and 80% adrenaline (epinephrine) are secreted here
What is Locus Ceruleus?
nucleus in the pons of the brainstem involved with physiological responses to stress and panic.
What is the Locus Ceruleus a principle site for?
brain synthesis of norepinephrine
What do neurons in the Locus Ceruleus send projections to?
axons that are leaving the centre and disputed all over the cortex and directed towards the thalamus
What does the brain appraise?
Threats
Gives it meaning
What brain regions are involved in the stress responses?
- Hypothalamus
- Amygdala (Limbic system)
- Locus ceruleus
What does the limbic system (amygdala) play a role in?
Appraisal/interpretation of the stressfulness of a threat
i.e. gives emotional meaning of perceptions: Fear, anger, anxiety
What is stress response?
Not just mechanical
It involves our emotions
What does the stress response operate via?
2 interrelated systems
- HPA (Hypothalamic-pituitary-adrenocortical)
- SAM (sympathetic-adreno-medullary)
Both triggered by the hypothalamus
Balance each other
What is SAM?
A stress response that bypasses the brain into medulla
What is SAM?
fast response
responds to short term stress
What is HPA ?
slow response
How does SAM work?
starts in the brain - specifically in the SNS
Signal the adrenal Medulla
chromaffin cells are the specific targets
Release epinephrine/norepinephrine in the blood
How does HPA axis work?
Start in the brain initially specifically in the hypothalamus move into the anterior pituitary release hormone called CRH release ACTH create cortisol
SAM
Adrenal medllula releases hormones epinephrine (adrenaline) and norepinephrine
What does SAM stimulate?
Rapid mobilization of metabolic resources:
- Increased heart rate
- BP
- Blood glucose
How does the epinephrine/norepinephrine stimulate the mobilization?
alpha and beta adrenergic receptors in the whole body
What does adrenal cortex produce?
- Glucocorticoid
- Mineralocorticoid
these form a back up response
What is the slower effect of cortisol the most important human glucocorticoid?
Involved in regulating metabolism
Immune response
General homeostasis
Alters metabolism from protein and fat into glucose
What is HPA involved in?
- Alters metabolism
- Supresses immune response
- Targets the brain: Receptors = GRs and MRs
- Alters gene expression via GR motifs in the genes
What do the glucocorticoid from HPA bind to?
Specific mineralocorticoid (MR) or glucocorticoid (GR) receptors on target organs
What does GRs mediate?
most of the stress response
What does MRs mediate?
Basal responses such as regulating:
- neurotransmitters
- BP
- Circadian rhythm
What is allostasis?
process of achieving stability, or homeostasis, through physiological or behavioral change
What is normal homeostasis maintained within?
Relatively narrow limits
What does the stress response maintain homeostasis over?
Far wider range of adaptive circumstances which allow organisms to respond to challenges
What is there not much in homeostasis?
Flexibility
What does maintaining stress and adaptive responses over long term imply?
High level of activation of the homeostatic processes
Define allostatic load
Allostatic load is “the wear and tear on the body” that accumulates as an individual is exposed to repeated or chronic stress
Why is chronic or severely acute activation of stress reponse maladaptive?
because when an individual stays in this space of exhaustion – its where diseases start to occur
What is General Adaptation syndrome?
==> Three predictable stages the body uses to respond to stressors
==> 1st stage: Alarm stage
- Provides a burst of energy
==> 2nd stage: Resistance stage
- The body attempts to resist or adapt to the stressor
==> 3rd stage: Exhaustion stage
- Energy is depleted
How are individuals not identical?
ʓ We come with different genetic mixtures, come from different maternal exposure, from different nutritional histories or immunological challenges
What can a genotype/ certain life experience contribute to?
- Vulnerable phenotype for the disease
What are susceptible phenotype sensitive to?
Environment
What causes gene expression changes in the brain?
- Chronic stress mixed with genetic predisposition
What can chronic stress lead to?
Cellular and molecular damage
Short period of stress
Release of neurotransmitters
Medium length
Corticosteroids
Transcription factors activated
Epigenetic effects
Chronic long term stress:
- Genomic and Epigenomic effects (DNA Methylation changes in neurons)
- Neurodegeneration
- Reduction in Neurotrophic production
What will sustained release of norepinephrine will produce ?
Adducts
What do different types of stressors have?
Different cellular characteristics
Define chronic stress
Maladaptive responses that can result in psychiatric syndromes such as anxiety and depressive disorders
