Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
WEEK 4:
Renal plasma flow, measurement and control, filtration fraction:
| Question | Answer |
|---|---|
| RPF | amount of plasma perfusing kidneys per unit time |
| importance of RPF | - Important determinant of GFR (↑RPF → ↑filtrate formed) - Can be used to estimate renal blood flow (RBF) - Both RPF and RBF are indicators of renal health. |
| indicator substance for estimating RPF requires | mass excreted = mass delivered to kidneys eg PAH (para-aminohippuric acid) |
| PAH features | freely filtered and secreted |
| total mass PAH excreted = | total mass PAH presented to kidney |
| UPAH .V = | PPAH.RPF |
| RPF = | UPAH .V/PPAH |
| RPF value | 600ml/min |
| effective renal plasma flow (ERPF) | |
| s7 | |
| clearance of PAH (UV/P) = | effective plasma flow |
| what is the clearance of PAH (UV/P) | plasma that is effective in urine formation (goes through urine producing blood vessels) |
| effective blood flow = | effective plasma flow / 1 - haematocrit |
| what is effective blood flow | blood that is effective in urine formation (goes through urine producing blood vessels) |
| total renal blood flow = | effective blood flow/ 0,9 |
| total renal blood flow refers to | blood that goes through renal artery |
| filtration fraction = | proportion of plasma that forms filtrate (0.2/20%) |
| FF = | GFR/ RPF (0.2) |
| the greater the filtration fraction the | higher the colloid osmotic pressure in peritubular capillaries (so greater forces for tubular reabsorption) |
| renal blood flow (RBF) can be derived from | RPF and packed called volume (PCV) |
| whole blood cellular fraction % | 40% |
| whole blood plasma fraction % | 60% |
| haematocrit (PCV) = | fraction of blood volume occupied by RBCS (0.4) |
| RPF = | 600ml/min (determined using PAH) |
| RBF = | RPF/ 1- haematocrit (1L/min) |
| RBF and GFR are constant over arterial blood pressures of | 90-180mmHg - which is caused by autoregulation and ensures fluid and solute excretion remains constant |
| myogenic mechanisms for afferent arteriolar resistance | afferent arteriole contracts in response to pressure and stretch |
| tubularglomeular feedback for afferent arteriolar resistance | – [NaCl] in filtrate sensed by macula densa of JGA (activity of Na+K+2Cl- cotransporter) & signal (adenosine) produced that contracts afferent arteriole and alters GFR: |
| macula densa function | detects changes in Na+ concentration and release adenosine/ATP causing vasoconstriction of afferent arteriole to filter less |
| slide 16 | |
| vasoconstrictors effect | decrease RBF and GFR |
| vasoconstrictors activated by | low blood pressure (eg haemorrhage) |
| what happens with vasoconstrictors | efferent arterioles are more sensitive to AgII than afferent at low conc so efferent constriction predominates and helps maintain GFR in presence of hypertension (both arterioles constrict at high concs of AgII dropping GFR) |
| effect of vasodilators | increase RBF and GFR |
| examples of vasoconstrictors | sympathetic nerves, angiotensin II |
| examples of vasodilators | prostaglandins, PGE2 and PGI2 |
| what happens with vasodilators | dampen excessive vasoconstrictor effects of sympathetic nerves and AgII and prevents severe renal vasoconstriction |
| clinical relevance of vasodilators + vasoconstrictors | |
| glycosuria | |
| causes of glycosuria (3) | steroid users, pregnancy and untreated diabetes mellitus |
| filtered glucose load | GFR x plasma glucose concentration |
| glucose excretion | urine flow (V) x urine glucose concentration |
| glucose reabsorbed | glucose filtered - glucose excreted |
Created by:
22tango
Popular Medical sets