Stress Sensitization Flashcards
Two stress response pathways?
Both controlled by PVN (paraventricular nucleus) of hypothalamus
1) Hypothalamic-Sympathetic-Adreno-Medullary (HSAM or SAM):
* Regulated by dorsal and ventral PVN
* Connects to brainstem
* Projections to organs of SNS
* Release of epinephrine and norepinephrine from medulla of adrenal gland
2) Hypothalamic-Pituitary-Adreno-Cortical (HPAC or HPA):
* Regulated by medial PVN
* Connects to pituitary (release ACTH)
* Release of cortisol from the cortex of adrenal gland
Feed-forward processes?
- Each part must dynamically adjust to inputs from the other parts.
- Frontal lobes —> limbic system —> Hypothalamus —> Brainstem.
- All parts contribute to the type and intensity of response.
- Response will vary depending on appraisals, motivations, arousal, and mood.
Hormones in Harmony: HSAM vs HPAC
HSAM (sympathetic activation) - short-term response:
* Epinephrine and norepinephrine regulation (Two types of catecholamines).
* Adrenergic (related to adrenaline).
* Aminergic (made from amino acids).
HPAC (HPA axis) - long-term response:
* Cortisol regulation
* Steroid hormone (made from cholesterol)
* Glucocorticoids are cortisol (in humans) and other similar hormones (corticosterone in rats)
The two systems work in harmony…. They talk to each other…and increase each other’s effects (sympathetic and HPA axis stronger impact on body)
Stress Hormones list?
Stress Hormones: Aminergic?
Made from amino acids
* Catecholamines (made from the amino acid tyrosine): Epinephrine, Norepinephrine, Dopamine.
* Serotonin (made from the amino acid tryptophan): Melatonin is derived from serotonin.
Steroid hormones?
- Made from cholesterol
- Glucocorticoids (has impact on most of the cells, tissues in the body):
1) Cortisol (in humans), Corticosterone (in rats).
2) Has effects on most cell types in the body. - Mineralocorticoids (Mainly involved in regulating balance of water and electrolytes).
- Sex hormones (Estrogen, testosterone, progesterone).
Two Major Stress Hormones
1) Epinephrine (adrenaline):
* Sympathetic activation (prime HPA axis to become active)
* Short-term stress response for immediate action
* Epinephrine at pituitary stimulates ACTH release
* ACTH in blood stimulates release of cortisol
2) Cortisol:
* Involved in normal metabolism (diurnal cycle)
* Does not initiate the stress response
* Regulates and maintains the stress response
* Make sympathetic nervous system more responsive to epinephrine
The Adrenergic Hormones?
Epinephrine (adrenaline) vs. Norepinephrine (noradrenaline)
Epinephrine vs. Norepinephrine (similarities and differences)
- Similar effects
- Both act as excitatory neurotransmitters (in CNS and PNS):
1) Norepinephrine involved in general arousal (in brain)
2) Epinephrine limited function as neurotransmitter (in brain) - Both released from the adrenal medulla
- Both increase heart rate, force of heart contractions
- Both increase metabolic energy (Increase blood sugar and release of fat stores)
- Epinephrine more impact on heart and lungs
- Norepinephrine more impact on blood vessels
Organs of the sympathetic nervous system contain what and activated by?
- Contain adrenergic receptors
- Activated by adrenaline/epinephrine or noradrenaline/norepinephrine
Adrenergic receptors are?
Alpha receptors and beta receptors
Alpha receptors?
- More activated by norepinephrine
- Typically leads to Vasoconstriction (squeeze the blood vessels)
- Can quickly increase blood pressure
Beta receptors?
- More activated by epinephrine.
- Typically leads to Vasodilation (relax the blood vessels).
- Increases heart rate (more blood go through).
- Beta receptors on vagus nerve ultimately connect to amygdala.
- Amygdala gets feedback from sympathetic activation (tell amygdala that adrenaline is going up).
Cortisol is part of? Circadian rhythm?
Cortisol is part of regular metabolism:
* Circadian rhythm (physical, mental, and behavioral changes that follow a 24-hour cycle) for cortisol production.
Cortisol permissive VS productive role
1) “Permissive” – normal levels of cortisol lets things happen
* “Maintain regularly scheduled program”
2) “Productive” – high levels of cortisol makes things happen
* “Shift focus to emergency tasks”
* Certain metabolic functions get prioritized over others
Cortisol is regulated by and part of?
1) Cortisol is part of regular metabolism
* Circadian rhythm for cortisol production.
* Regulated by sleep-wake cycle, influenced by hours of “daylight”.
Wake up - cortisol levels high (peaks in morning) and then decreases throughout the day; low cortisol - when we sleep, drops in cortisol help you fall asleep.
Circadian Rhythm of Cortisol Regulation? Which parts of brain?
- Suprachiasmatic nucleus (SCN) of hypothalamus
- Receives visual info from thalamus
- Day-night cycles detected from light exposure
- SCN regulates daily activity of PVN
Functions of Cortisol? Why its needed?
Cortisol is called a stress hormone, but is needed for normal homeostatic functioning:
* Has a wide range of effects.
* Cortisol does not trigger a stress response. It regulates the stress response.
* The presence of cortisol by itself should not be considered a sign of stress.
(Cortisol levels should never get high because of negative feedback mechanisms.)