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39 Cards in this Set
- Front
- Back
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List the 2 arms of the stress axis.
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1. HPA axis
2. Sympatho-adrenomedullary axis |
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Increase expression of gluconeogenic enzymes and adrenoreceptors is a result of which arm of the stress axis?
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HPA axis
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Rapid gluconeogensis, vasoconstriction, and increased heart rate are responses to which arm of the stress axis?
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Sympatho-adrenomedullary axis
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Describe the hypothalmo component of the HPA axis
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Neurons in the paraventricular nuclei express and release CRH
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Describe the anterior pituitary component of the HPA axis.
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Corticotrophs express proopiomelanocortin and secrete ACTH
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Where is the primary capillary plexus located?
Which neurons secrete hormones here? |
Located in the median eminence
Paraventricular neurons secrete hormones (such as CRH) in the primary plexus, which are destined for the anterior pituitary |
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How are hormones carried from the primary capillary plexus to the anterior pituitary?
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Long portal vessels extend from primary capillary plexus to second capillary plexus in the anterior pituitary
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In the anterior pituitary, POMC is processed into which derivatives?
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1. ACTH
2. B-endorphin |
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In the neurointermediate lobe of the pituitary, POMC is processed into which derivative?
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a-MSH
(melanocyte-stimulating hormone) |
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Neurons in the CNS process POMC into which derivatives?
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1. B-endorphin
2. a-MSH 3. y-MSH |
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Describe the ACTH receptor and which pathway it activates.
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G-protein coupled receptor
Activates adenylate kinase --> increases cAMP --> activates Protein Kinase A ---> steroidogenesis |
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What is the acute effect of PKA on steroidogenesis?
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1. Activates hormone sensitive lipase/ cholesterol esterase ---> liberates cholesterol from cholesterol stores
2. Activates StAR |
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What is the chronic effect of PKA on steroidogenesis?
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Regulates expression of SF-1 (steroidogenic factor 1)--transcription factor
SF-1 regulates expression of enzymes involved in steroidogenesis AND StAR *Increased delivery of cholesterol + increased mass of enzymes |
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When do ACTH and cortisol peak during the day?
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During early morning hours (post-waking; ~8am)
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When are ACTH and cortisol levels the lowest during the day?
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In the evening
(8 - 10 pm) |
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What sort of releasing pattern do ACTH and cortisol follow?
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Circadian (diurnal)
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Will chronic or repeated stressors have more of an effect on daytime or nighttime cortisol levels?
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Daytime (nadir will be elevated)
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Describe the effects of stress-activated cortisol production (negative feedback system).
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1. Elevated cortisol stimulates limbic centers for feedback (hippocampus)
2. Results in decreased CRH, decreased ACTH, and decreased cortisol production |
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If ACTH levels are normal or elevated and they are suppressed by a high dose of Dexamethasone, what condition is most likely?
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Pituitary Cushing's disease
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If ACTH levels are normal or high and they do not respond to Dexamethasone, what is the most likely diagnoses?
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Ectopic ACTH-producing tumor
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If ACTH levels are undetectable or low, and they are not affected by Dexamethosone, what is the most likely diagnosis?
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Primary Cushing's syndrome
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What is the mode of action of Metyrapone?
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Inhibits P450-C11.
(blocks cortisol production) |
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Describe the Metyrapone stimulation test.
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Cortisol production is blocked, which an expected rise in ACTH and CRH (if normal).
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What is the effect of glucocorticoids on glucose uptake and protein synthesis in muscle?
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Inhibits glucose uptake
Inhibits protein synthesis (stimulates protein breakdown to liberate amino acids for gluconeogenesis) |
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What is the effect of glucocorticoids on adipose tissue?
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1. Liberate fatty acids for gluconeogenesis
2. Stimulates adipocyte differentiation and redistribution of fat |
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How do glucocorticoids stimulate gluconeogenesis?
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Increased expression of:
1. PEP carboxykinase 2. Fructose 1,6 bisphosphatase 3. Glucose 6-phosphatase |
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How do glucocorticoids stimulate glycogen storage?
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Increased expression of glycogen synthase
Decreased expression of glycogen phosphorylase |
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Glucocorticoids stimulate Lipocortin-1 in leukocytes-- what is the effect of lipocortin-1?
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1. Inhibits adhesion of leukocytes to vascular wall
2. Inhibits migration/ extravasation 3. Inhibits phagocytosis |
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How do glucocorticoids result in hypertension?
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1. Increase expression of adrenergic receptors
2. Increases PNMT expression 3. Increase sodium and water retention |
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What is the effect of steroids on the hippocampus?
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Chronic use will decrease volume, resulting in memory loss
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What is the effect of steroids in the limbic system?
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Increased fear and anxiety
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What is the effect of steroids on sleep?
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Decreases REM sleep
Increases slow wave sleep |
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What is the effect of acute stress on heart rate, cardiac output, and peripheral resistance?
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All are increased
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What is the effect of epinephrine on heart rate, cardiac output, and peripheral resistance?
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Heart rate + cardiac output = increased
Peripheral resistance = decreased |
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What is the effect of norepinephrine on heart rate, cardiac output, and peripheral resistance?
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Heart rate + cardiac output = decreased
Peripheral resistance = increased |
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What is the effect of steroids on glycogen metabolism?
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Increases glycogenolysis in muscle and liver
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List the metabolic actions that steroids have on adipose tissue.
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1. Increased lipolysis, fatty acid liberation
2. Increased glycerol liberation 2. Decreased adiposity |
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List the metabolic actions of steroids on the liver.
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1. Increased glycogenolysis
2. Increased gluconeogensis 3. Increased fatty acid oxidation 4. Increased pyruvate to lactate release |
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What is the effect of steroids on the pancreas?
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Inhibits insulin release
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