Week 17 Physiology

Renin-Angiotensin system (popular question):

Ganong's Review of Medical Physiology, 24th Edition

Ganong’s Review of Medical Physiology, 24th Edition

  • Synthesis of renin / angiotensin.
    • Prerenin synthesised in kidney and other tissues eg ovaries but activated to renin only in kidney(juxtaglomerular cells)
    • Angiotensin made from ACE in endothelium esp in pulm circulation
  • Actions.
    • Renin –> converts angiotensinogen to angiotensin 1
    • Angiotensin 2 –> vascoconstriction(increase SBP and DBP), Aldosterone secretion, vassopressin secretion, cause thirst, facilitate release of NA, contraction of mesangial cells–> reduce GFR, increase Na reapsorption directly in renal tubules. Decreases sensitivity of central baroreceptors. Increase ACTH.
  • Regulation of renin secretion
    • Renin secretion
      • Renal nerves firing
      • Increased catecholamines
      • Prostaglandins
      • Hypotension/haemorrhage/diuretics/dehydration
      • Cirrhosis
      • Cardiac failure
      • Upright posture
      • Na wasting
    • Renin secretion inhibition
      • Angiotensin II
      • Vasoppressin
      • Increased Na and cl absorption at macula densa
      • Increased afferent arteriolar pressure
      • Inhibit PGs eg by indomethacin
      • Inhibit catecholamine levels eg via B blockers



  • Synthesised by kidneys to stimulate RBC production, angiogenesis, vasocontriction, smooth muscle proliferation.
  • Stimulated by hypoxia, anaemia,
  • Made in peritubular cells of renal cortex.


Atrial natriuretic polypeptide:

  • Secreted in response to expansion of ECF and increased NaCl intake
  • Causes natriuresis
  • Made in heart
  • Actions
    • Dilate afferent arterioles and relax mesangial cells to increase GFR
    • Inhibit renal tubular reabsorption of Na
    • Relax vascular smooth muscle and increase capillary permeability
    • Inhibit renin secretion
    • Inhibit the vasopressor effects of Angiotensin 2 and catecholamines
  • Factors affecting secretion.
    • Increased ECF –> atrial and ventricular stretch
    • Admin of thiorphan
    • Immersion in water up to neck


Viva questions:

  • Tell me about the Renin-Angiotensin system.
  • What things stimulate renin secretion ?
  • Tell me about Erythropoietin.
  • What factors stimulate Erythropoietin secretion ?
  • What are the endocrine functions of the kidney ?
    • Renin secretion.
    • Erythropoietin secretion.
    • Performs the 1-hydroxylation in the production of 1, 25-dihydroxycholecalciferol (the
    • active metabolite of Vitamin D3.
    • Production of kinins.