RAAS

• Low blood pressure is detected by baroreceptors in the carotid sinus and aortic arch. Juxtaglomerular cells in the tunica media of the afferent arterioles also detect low blood pressure.
• Baroreceptors stimulate the sympathetic nervous system to stimulate renin secretion from the kidneys.
• Macula densa detect low chloride and sodium ions in the tubules (kidney).
• Angiotensinogen is made in the liver. Renin converts this to angiotensin I. This is converted to angiotensin II by ACE. ACE can be found in the surface renal and pulmonary epithelium.
• Angiotensin II’s effects:

  • causes the efferent arteriole to constrict more than the afferent arteriole -> increases glomerular filtration rate
  • proximal tubule reabsorbs more sodium ions
  • increases thirst
  • increases blood pressure via vasoconstriction of blood vessels
  • increases ADH secretion from the posterior pituitary which increases water reabsorption
  • stimulates aldosterone secretion from the zona glomerulosa of the adrenal glands
• Aldosterone’s effects

  1. binds to intracellular receptors of principal cells in the CT
  2. increases production of sodium potassium ATPase pumps
  3. increases hydrogen ion secretion from alpha intercalated cells in the PCT
• RAAS increases the perfusion of the juxtaglomerular apparatus
• perfusion is the flow of blood to a specific part of the body. poor perfusion means that there is reduced blood flow to that area of interest.