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