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What is the primary mineralocorticoid, its function, and where is it secreted from?
- Aldosterone - increases Na reabsorption at nephron, sweat, stool, saliva
- Zona glomerulosa
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What are the controls of aldosterone secretion?
- Renin-Angiotensin
- Serum K+
- ACTH
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Systems for fluid/electrolyte homeostasis
- Renin-Angiotensin-Aldosterone
- ADH
- Thirst
- Na appetite
- ANH
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What drug blocks aldosterone receptors?
Sprionolactone
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Effects of Aldosterone on:
1. Na
2. K
- 1. Increases reabsorption
- 2. Facilitates passive excretion
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Describe the Renin-Angiotensin System
- Juxtaglomerular apparatus secretes renin
- Renin cleaves angiotensinogen to angiotensin I
- Angiotensin I converted to angiotensin II by ACE (Angiotensin Converting Enzyme)
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Describe ACE Inhibitors
- Prevent Angiotensin II synthesis
- Decrease aldosterone synthesis
- Decrease Na reabsorption, ergo water reabsorption
- Treat hypertension
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What stimulates renin synth?
- Decrease in perfusion pressure (baroreceptors)
- Hypotonic fluid in macula densa (chemoreceptors)
- Sympathetic innervation in response to decrease in plasma volume
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Describe Primary aldosterone excess
- Hyperactive tumors of the adrenal gland (rare)
- Cause hypokalemia and hypertension/hypernatremia
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Describe Secondary Aldosterone excess
- Decreased effective blood volume (edema)
- Sustained high levels of renin
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What is the primary function of adrenal androgens?
Maturation of secondary sex characteristics
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What is the major function of the adrenal medulla?
- Secrete catecholamines (epinephrine, norepinephrine)
- Allows for systemic stress response
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What are the secretory cells of the adrenal medulla?
Regulation?
- Chromaffin cells - secrete catecholamines
- Regulated by sympathetic NS
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What are the receptor types for catecholamines?
A and B adrenergic
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What are the systemic responses to catecholamine release?
- Cardiovascular output increase
- Mobilization of energy stores
- Arousal (pupillary dilation, piloerection, tachycardia)
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What is the common cause of catecholamine excess?
- Pheochromocytoma
- Catecholamine secreting tumor
- Yields same systemic flight or fight response
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