Stress Flashcards
hypofunction of stress can lead to
boredom or depression
hyperfunction of stress can lead to
anxiety or poor health
what stimulates the fight/flight sympathetic NS?
the hypothalamus activates SNS (f/f response) by releasing epinephrine or norepinephrine
what does the release of epinephrine/norepinephrine from hypothalamus trigger?
this stimulates the release of EP and NE from adrenal medulla which activates body cells, endocrine glands, then finally the brain
how long does the f/f response last? what influences how long it lasts?
Dont last a long time. There is feedback through vegas nerve. This leads to rapid physiological adaptation (alertness, vigilance, appraisal, f or f) → rapid responses and short term effects
how is threat communicated to the hypothalamus?
the medulla (the control center for SNS response) gets input from amygdala
what are the two endocrine responses to stress? (structure and speed/effects)
medulla- releases adrenaline (epinephrine) to generate a fast response
cortex- releases glucocorticoids (cortisol) to generate a slower, longer-lasting response
A stressor causes a long term stress response process to start. What happens in this process?
Hypothalamus secretes CRH (Corticotropin-releasing hormone) → anterior pituitary releases (in ~15 sec) ACTH signals to the cortex of the adrenal gland → ACTH stimulates cortisol release form adrenal cortex (in ~ a couple minutes). Cortisol (has metabolic effects and serves as negative feedback signal) activates body’s cells, endocrine glands, brain, etc. peak of cortisol release is at 10 min
what is the CRH (Corticotropin-releasing hormone)
regulates the hypothalamic-pituitary-adrenal (HPA) axis (the main organizer of the body’s response to stress.
where is CRH secreted from?
secreted from the hypothalamus
what structure does CRH stimulate
stimulated the anterior pituitary to release adrenocorticotropic hormone (ACTH)
what does ACTH target?
ACTH then acts on its target organ, the adrenal cortex.
what are tropic hormones?
hormones that stimulate other endocrine glands so as to produce their particular hormones. They are produced and secreted by the anterior pituitary gland. They play a vital role in influencing the function, growth, and nutrition of other endocrine cells.
what is a metabolic stress response and what does it help with/what are some examples?
Mobilize energy (to get moving): inhibits energy storage
- Inhibit insulin (blocks breakdown of triglycerides in fat tissue, promotes glucose uptake)
- Inhibit ovulation in females, reduces testosterone in males (reproductive stress response)
- Vasoconstriction, increase bp (cardiovascular stress response )
- Inhibit pain perception, immune system, tissue repair
Short term stress response
- Glycogen broken down to glucose; increased blood glucose
- Increased bp
- Increased breathing rate
- Increased metabolic rate
- Change in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity
Long term stress response
Mineralocorticoids released from adrenal cortex
1. Retention of sodium ions and water by kidneys
2. Increased blood volume and bp
Glucocorticoids released from adrenal cortex
1. Proteins and fats broken down and converted to glucose, leading to increased blood glucose
2. Immune system may be suppressed
Metabolic stress response
Mobilize energy (to get moving): inhibits energy storage
- Inhibit insulin (blocks breakdown of triglycerides in fat tissue, promotes glucose uptake)
- Inhibit ovulation in females, reduces testosterone in males (reproductive stress response)
- Vasoconstriction, increase bp (cardiovascular stress response)
- Inhibit pain perception, immune system, and tissue repair
Hypothalamic pituitary adrenal axis (HPA)
How is the threat communicated to hypothalamus?
Afferent innervation of hypothalamus
Paraventricular nucleus (PVN) of hypothalamus input:
Amygdala:
Dorsal raphe nucleus:
Locus coeruleus:
Central gray
Circumventricular organ: bloodborne chemosensory input - important in negative feedback
Sympathetic: Physiological changes
HPA: Metabolic response
Acute vs Chronic stress
Acute: seconds- hours
Hippocampus: neurologically- neurogenesis, behaviorally - improved memory
Ex: acute stress in rats (immobilization)
Acute response is some cortisol release. Stem cells in hippocampus make new neurons. You see this lead to improved mental performance two weeks later. Astrocytes mediate this effect of neurogenesis by releasing growth factors (FBF2) (structural change))
Chronic: hours - decades
Hippocampus: atrophy, behaviorally - impaired memory
Ex: rats immobilized
Chronic - excessive release of cortisol. Reduces neurotrophic factor release. Atrophy of hippocampal neurons (reduced survival and growth). Hippocampus is vulnerable to damage with stress but reversible
Hippocampus critical in ending stress response (communicates with hypothalamus)
More cortisol secretion destructs hippocampal neurons leading to fewer hippocampal neurons which then decreases ability to shut off cortisol secretion
Chronic amygdala
Expansion of neurons
Increase nerve excitability
- Risk of anxiety disorders
What is chronic immobilization stress (CIS)? what are some findings about stress and its structural and behavioral effects?
a chronic stress model used to invoke stress in model animals and determine the effects
FOUND: Structural effects of amygdala - increased dendritic branches and increased dendritic spines
Accompanied by development of anxiety-like behavior on elevated plus- maze
When does stress result in pathology?
Many factors interact
Timing, duration, individual variability (genetics)
Ex: individuals who felt they had little sense of purpose were more likely to die within a few years after diagnosis of heart disease
Overstimulation by same hormones that enable adaptation on short term basis
Outcome of stress response determined by intensity, length, frequency (acute vs chronic)
Chronic stress surpasses regulatory capacity of organisms can lead to maladaptive responses
what were some of the effects in humans’ stress levels who were in an 8 week meditation intervention
stress reduction correlates with structural changes in the amygdala
Reduction in perceived stress rating
Decrease in right amygdala gray matter density
