Volume Regulation Flashcards
What is the nephron?
the fundamental functional unit of the kidney
Why is the effective circulating volume measured instead of the extracellular water content?
Because the body can’t easily measure the total extracellular water content
What is the juxtaglomerular apparatus?
the complex of late distal tubule in association with renal afferent arteriole
What is the macula densa?
the thickening of the wall of the early distal tubule
What is the aim of the renin-angiotensin-aldosterone system?
to increase the effective circulating volume
What happens when there is a low Na+ conc in the distal tubule?
look at diagram on lecture
What are the effects of producing angiotensin II?
- efferent arteriole vasoconstriction (increase in hydrostatic pressure, increase in filtration rate) keeps GF in nephron
- increase Na+ reabsorption in proximal tube (causes water reabsorption increasing volume without changing osmolality)
- can cause aldosterone release from adrenal cortex which increases Na+ reabsorption by distal tubule and collecting duct ( same as earlier mechanism)
What are the two main physiological triggers for aldosterone release?
ATII
hyperkalaemia
What is the other role of aldosterone?
control of K+ secretion
What does spironolactone block?
effect of aldosterone
Where does spironolactone act?
in the collecting tubules and ducts
What are the uses of spironolactone?
heart failure (K+ sparing diuretic)
What 4 locations in the renin angiotensin system can be used to control blood pressure?
- ACE inhibitors
- AT1 receptor antagonists
- Aldosterone receptor antagonists
- renin inhibition
What is the main receptor for angiotension II?
AT1 receptor
What are the effects of angiotensin II?
- vasoconstriction
- increase Na+/H+ exchange in the proximal tubule. and hence proximal Na+ and water reabsorption
- increase in aldosterone release from the adrenal cortex, which increases distal Na+ absorption
- causes ADH release
- Causes thirst
