Hormonal Control of BP

Question 1

describe renin

Answer 1

• protein enzyme released from granular cells of JG apparatus
• secretion stimulated by:
  
  • decreased arterial pressure –> decreased renal perfusion pressure
  • decrease in NaCl sensed by macula densa cells
  • increased activity of renal sympathetic nerves
• action:
  
  • catalyzes conversion of AG to AGI

Question 2

describe AGII

Answer 2

• powerful controller of Na reabsorption
• secretion stimulated by:
  
  • decreased arterial pressure -> decreased RPP
  • low Na intake
• actions:
  
  • stimulates aldosterone secretion from adrenal glands
  • vasoconstriction of renal arterioles
  • stimulates thirst
  • increase NaCl reabsorption in prox. tubule
  • increases Na/H exchanger in prox. tubule (therefore also aids in bicarbonate reabsorption)

Question 3

describe aldosterone

Answer 3

• secreted by glomerulosa cells of adrenal cortex
• binds to basolateral receptors on principal cells of LD/CD
• directs synthesis of proteins involved in Na reabsorption (luminal membrane Na channel, Na/K/ATPase)

Question 4

what stimulates the secretion of aldosterone

Answer 4

• AGII
• hyperkalemia (high plasma [K])
• hyponatrermia (low plasma [Na])

Question 5

what are the actions of aldosterone

Answer 5

• increase Na/H2O reabsorption by principal cells in LD/CD
• increase K secretion
• increase H+ secretion from alpha-intercalated cells (H-ATPase pump)
• pathophys:
  
  • Addison’s Disease = adrenal insufficiency
  • Conn’s syndrome = hyperaldosteronism

Question 6

describe what stimulates ADH secretion

Answer 6

peptide hormone secreted by posterior pituitary

• secretion stimulated by:
  
  • increased plasma osmolarity of 1mOsm/L (most important stimulus)
  • hypovolemic loss of >8% ECF (most potent stimulus)
    
    • volume overrides tonicity

Question 7

describe the actions of ADH

Answer 7

• allows formation of water channels in the LD/CD increasing reabsorption of water -> increases urine osmolarity and decreases urine flow volume
• increases H2O permeability (V2 receptors)
• increases contraction of vascular smooth muscle (V1 rec.)
• actions on renal tubule
  
  • increases H2O permeability
  • increases NKCC effectiveness
  • increases urea permeability
• pathophys
  
  • central/nephrogenic diabetes insipidus: decreased
  • SIADH: increased

Question 8

describe ADH mechanism

Answer 8

• ADH binds to V2 receptor
• G-protein coupled receptors increase cAMP
• increase in cAMP cause the insertion of aquaporins to facilitate H2O reabsorption

Question 9

describe the function of ANP

Answer 9

receptors found in DT/CD but not prox. tubule

• vasodilation of afferent arteriole and constriction of efferent arterioles

Question 10

name the load-dependent portions

Answer 10

• thick ascending loop of Henle
• early DT