Stress and Stress Diseases Flashcards
What is the stress response?
Neuroendocrine control systems that mediate physical, emotional, and behavioral reactions to stressors.
Negative feedback
Neuroendocrine control system facilitates a change in the body, then stops or activates a pathway with an opposite effect when adequate response occurs
This maintains homeostasis!
How is regulation of blood glucose an example of negative feedback?
- Increase in blood glucose
- Beta cells in pancreas release insulin
- Insulin binds receptors on cells and increases the availability of glucose transporters
- Blood glucose levels fall
- Insulin secretion is inhibited
- Glucagon is released from alpha cells of hte pancreas and stimulates release of glycogen stores from the liver
- Blood glucose rises
Positive feedback
Cycle where initiating stimulus produces more of the same response
CREATES INSTABILITY
What is an example of positive feedback?
Oxytocin in birthing
What is the HPA axis and why is it important?
Hypothalamic-pituitary-adrenal axis
Endocrine control of stress response occurs as a hormonal cascade from the paraventricular nucleus of the hypothalamus, anterior lobe of the pituitary, to the adrenal gland ending in cortisol secretion.
In what way can stress be beneficial?
It can be a stimulus for emotional growth and development
BUT positive stressors (like having a baby) can have a similar physical effect of negative stressors
What are conditioning factors?
Internal (genetic predisposition, age, gender) and external (diet, social support, environment) influencers on a person’s ability to adapt to stress through physiological response.
Allostasis
Interactive physiological changes in the neuroendocrine, autonomic, and immune systems that occur in response to instability; or
the body’s attempt to maintain stability by reacting to stressful stimuli
Allostatic load
Accumulation of allostatic changes (immune suppression, sympathetic NS, and renin-angiotensin-aldosterone system)
Function of the cerebral cortex
Mental capacities - vigilance, cognition, focused attention in stress response
Function of limbic system in stress response
Emotions (fear, anger, excitement)
Function of thalamus in stress response
relay center - receives, sorts, and distributes sensory information
Function of hypothalamus in stress response
Coordinates responses of the endocrine and autonomic nervous system (releases CRF and stimulates locus ceruleus)
Function of reticular activating system (RAS)
Modulates mental alertness, ANS activity, and skeletal muscle tone through reflex circuits
What is the locus ceruleus?
Part of the brain stem with lots of neurons that produce NT norepinephrine (integrating site for ANS response to stress) when it receives sensory info from different parts of the brain. Responsible for increased attention and alertness, thought to improve memory during stress.
What does the adrenal medulla secrete in the stress response?
Norephinephrine and epinephrine
What is the body’s physiological response to epinephrine and norepinephrine release?
- decrease in insulin release and increase in glucagon release (increased gluconeogenesis, lipolysis, proteolysis)
- increased cardiac contractions, vascular smooth muscle contractions, and heart rate
-relaxation of bronchial smooth muscle
What hormone does the hypothalamus release in the stress response?
Corticotropin-releasing factor (CRF)
What effect does Corticotropin-releasing factor (CRF) have on the body?
- stimulates ACTH release from the pituitary gland
- increased activity of neurons in locus ceruleus
What hormone does the anterior pituitary gland release during the stress response?
Adrenocorticotropic hormone (ACTH)
what affect does ACTH have on the body?
-stimulates synthesis and release of cortisol after release into circulation and binding to the adrenal gland receptors
What hormone does the adrenal cortex produce in the stress response?
Glucocorticoid hormones (CORTISOL)
- this is a steroid hormone
How does cortisol affect the body?
- enhances the action of epinephrine and glucagon
- inhibits release or action of reproductive hormones and TSH
- decreases the number of immune cells and inflammatory mediators
IN SUM: regulates metabolic, immune, cardio, and behavioral responses to stress and maintains homeostasis through negative feedback. allows us to survive stressors and allows our bodies to come back to homeostasis after stressor subsides.
Where are mineralocorticoid hormones released? (ex. aldosterone)
What do they do?
The adrenal cortex
Increases sodium absorption by the kidney
How is the renin-angiotensin-aldosterone system (RAAS) involved in the stress response?
-aldosterone release increases sodium and water retention (peeing is not a priority when stressed)
-angiotensin II enhances CRF release in the hypothalamus, ACTH release from the pituitary, vasopressin release from the posterior pituitary, and norepinephrine from the locus ceruleus
What part of the stress response results in pupil dilation, sweaty hands and feet, dry mouth, reduced activity of GI, and increased heart and respiratory rate?
The sympathetic nervous system (ANS), which is enhanced by epinephrine and norepinephrine hormonal release from the adrenal medulla
How is antidiuretic hormone involved in the stress response? Where is it released from?
It is released from the posterior pituitary
It is a vasopressin- it increases water retention by the kidneys and vasoconstriction of blood vessels (fluid retention = more fluid in BVs = more pressure on walls of BVs = High BPH)
-more active in hypotensive stress or stress due to fluid volume loss (again, an attempt at homeostasis!)
What do cytokines do?
They are chemical messengers that are involved in inflammatory and stress response. Released by monocytes and lymphocytes, which can cross the BBB. Involved in activating tissue repair and increasing WBCs,
How does physiologic reserve contribute to our ability to adapt to stress?
Body systems have a large safety margin and can increase their level of function as a form of adaptation (ex: hypertrophy of kidney after nephrectomy)
our cells produce/carry more substances than is needed
What are the stages of Selye’s general adaptation syndrome?
- Alarm stage: activation of SNS and HPA axis
- Resistance stage: body selects more effective defenses
- Exhaustion stage: physiologic resources are depleted and signs of systemic damage appear
What pathophysiology explains PTSD as a chronic stress disorder?
Results from the exaggerated stress response and failure of the neuroendocrine system to maintain homeostasis.
Recent research shows increases SNS activity, but low levels of cortisol and inhibition of negative feedback of cortisol.
Increased reactivity of the amygdala and hippocampus and decreased activity of the anterior cingulate and orbitofrontal areas (area involved in fear response
