4. Control Of Body Fluid Volume Flashcards
What is renin?
An enzyme that is synthesised and stored in the JGA in the kidneys
A fall in plasma Na+ leads to a fall in ECF volume, causing the release of renin
What causes the stimulation and release of renin?
Increased sympathetic innervation - granular cells of JGA are innervated by sympathetic system
Wall tension in afferent arterioles falls - change in BP decrease wall tension at granular cells
Decreased Na+ to macula densa
How does angiotensinogen get converted to angiotensin 1 and angiotensin 2?
Angiotensinogen to angiotensin 1 = Renin
Angiotensin 1 to angiotensin 2 = ACE
What is the role of angiotensin 2?
Directly vasoconstriction arterioles within the kidney (efferent>afferent)
Stimulates zona glomerulos of the adrenal cortex to release aldosterone
What does aldosterone do?
Directly increase Na+ reabsorption from the PCT
Releases ADH
Stimulates thirst
What are the starlings forces in the PCT?
Amount of Na+ reabsorbed into peritubular capillaries from the PCT depends on the rate and amount of uptake from the intercellular spaces into the capillaries
What is the role of prostaglandins?
A decrease in effective circulating volume stimulates cortical prostaglandin synthesis
Where does cortical prostaglandin synthesis occur in the kidney?
Cortex - arterioles and glomeruli
Medullary interstitial cells
Collecting duct epithelial cells
What do prostaglandins result in?
Vasodilators - preventing excessive vasoconstriction
Renin release
What is atrial naturetic peptide produced by?
Cardiac atrial cells in response to an increase in ECF volume
What does atrial naturetic peptide do?
Inhibits Na+/K+ ATPase and close Na+ channels of the collecting ducts and PCT, reducing Na+ reabsorption, Na+ and water excretion is increased
Vasodilation afferent arterioles, increasing GFR
Inhibit aldosterone secretion
Inhibit ADH release
Decrease renin release
What are the effectors of change in renal sodium excretion?
- Changes in osmotic pressure and hydrostatic pressure alter the proximal tubule Na+ reabsorption
- Proximal tubule Na+ reabsorption stimulated by AGII under conditions of low BP
- Principle cels of DCT and CD targets for aldosterone
- When renal artery BP increases
How does the renal artery BP increasing change renal sodium excretion?
Reduced number of Na-H anti porter and reduced Na-K ATPase activity in proximal tubule
What is pressure natriuresis?
Increased sodium excretion
What is pressure diuresis?
Increased water excretion
