Renin-Angiotensin-Aldosterone System Flashcards
where is the RAAS controlled?
kidney
what structure in the kidney controls the RAAS?
juxtaglomerular apparatus
what does the juxtaglomerular apparatus consist of?
JG cells & macula densa
where are JG cells located?
afferent & efferent arterioles
what is the function of JG cells?
make and secrete renin (enzyme)
where is the macula densa located?
distal convoluted tubules between afferent & efferent arterioles
what is the macula densa sensitive to?
- low NaCl
- low BP
- increased sympathetic stimulation (beta adrenergic stim by E)
what is the function of the macula densa?
(turns on RAAS)
- stimulate JG cells to release renin
- release NO
what is the effect of NO released from the macula densa?
dilate afferent arteriole
what happens to GFR when the afferent arteriole is dilated?
increases
what does renin do?
convert angiotensinogen (from liver) -> angiotensin I (in blood)
where is angiotensin coverting enzyme (ACE) located?
lung
what is the function of ACE?
converts angiotensin I -> angiotensin II (in blood)
what are the functions of angiotensin II?
- release aldosterone from zona glomerulosa (adrenal glands; increases Na/K pump)
- constrict efferent arteriole
what happens when the efferent arteriole is constricted?
- increases GFR & decreases urine volume
- leads to increased blood volume & BP
what is the function of aldosterone in the RAAS?
- causes increase in blood Na concentration
-> causes release of ADH
-> increases blood volume & BP
what are the only 2 things that can constrict the efferent arterioles?
ADH and angiotensin II
if a tumor or pathology exists in a pathway, what happens to everything before and after that step?
decrease before
increase after
if a drug functions to block a step of a pathway, what happens to everything before and after that step?
- increase before (attempt to increase next step)
- decrease after (blocks action)
what percent of filtrate is reabsorbed?
99%
what happens to blood volume and urine volume when filtrate is reabsorbed?
increased blood volume
decreased urine volume
dilation of the afferent arteriole leads to what physiological changes?
- vasodilation
- increased compliance
- increased hydrostatic P
- increased blood flow
- decreased resistance
constriction of the efferent arteriole leads to what physiological change?
vasoconstriction
dilation of the afferent arteriole in combination with constriction of the efferent arteriole leads to…
increased GFR
increased BP
what effect would a 50% decrease in efferent arteriolar resistance have on GFR?
large decrease in GFR (greater than 10%)
increases in both renal blood flow and GFR are caused by what mechanism?
dilation of afferent arterioles
(increases glomerular hydrostatic P -> increases GFR & renal blood flow)
