Renin-angiotensin system Flashcards
What happens when blood pressure falls (immediate response)
Immediate activation of baroceptosr in major blood vessels and heart
What do baroceptors do
Increase sympathetic outflow from the CNS to produce immediate mechanisms to raise blood pressure
What is long term restoration of blood determined by
Kidney
What happens in the kidney
Lots of blood is filtered in the kidney and most is reabsorbed. We have mechanisms that control how much is reabsorbed
What does the juxtaglomerular apparatus do
Regulates salt and fluid balance
What do the cells in afferent arteriole do
Sample blood to kidney
What are the macula dense sensitive to
Alterations in salt concentrations
What do the granular cells do
cells in the kidney that synthesize, store, and secrete the enzyme renin
What happens when the volume of blood is low
Cells of juxtaglomerular apparatus sense volume and release renin
What are the stimuli for renin release
- Decreased renal perfusion pressure (detected by granular cells)
- Decrease NaCl concentration (detected at macula densa)
- INcreased sympathetic nerve activity (via action of beta1 adrenoceptors)
What happens in the angiotensin system
1) angiotensin made by liver
2) Renin (enzyme) breaks down angiotensin
3) Converted into angiotensin 1
4) angiotensin 1 converted to angiotensin 2 by angiotensin converting enzyme found in lungs
5) This causes the release of hormone andosterone
6) andosterone controls volume regulation
What does andosterone do
Increase retention of sodium and water
What are the actions of angiotensin 2
- VAsoconstrictor (increase peripheral resistance and hence blood pressure)
- Enhances sympathetic nerve function
- Increase release of aldosterone
- Release vasopressin (ADH)
Action of vasopressin
- vasoconstriction
- Increases fluid retention
Why does ADH increase fluid retention
Increases number of aquaporin-2 channelise the distal tubes/collecting duct of the kidney
