Renal Circulation Flashcards
What is the equation for Renal Plasma Flow
RPF= RBF x (1-Hct)
What is the equation for Filtration fraction?
FF= Glomerular Filtration Rate/ Renal Plasma Flow
How much of the CO do the kidneys receive?
~20-25% of CO
What are the two major factors that generate filtrate?
- Hydraulic pressure in glomerular capillaries
2. Renal blood flow rate
What other factors contribute to filtrate formation?
Hydraulic pressure
Renal blood flow rate
Minor- Blood oncotic pressure
Filtration coefficient (how easily you can move fluid across: characteristics of vessel, SA)
What is the equation for blood flow?
Flow (Q)= Pressure Change/Resistance
What factors influence resistance in the vessels?
- Length of blood vessels
- Radii of blood vessels (MAJOR factor)
- Blood viscosity
What are the effects of vasoconstriction?
Decreased flow
pressure up stream increases
downstream pressure decreases
B/c of the presence of of both pre- and post- glomerular capillary sphincters:
- Glomerular capillary pressure is much (greater/less) than in most capillaries elsewhere in the body.
- Peritubular capillary pressure is (higher/lower) than in most capillaries elsewhere in the body
- greater
- lower
These pressure differences facilitate formation of filtrate in glomeruli and reabsorption of fluid from peritubular capillaries.
What are three factors that promote renal constriction?
- Sympathetic n (catechoamines)
- Angiotensin II
- Endothelin
What are 5 factors that promote renal constriction?
- PGE2
- PGI2
- NO
- Bradykinin
- Dopamine
What effect do sympathetic nerve fibers have?
They activate alpha 1 receptors on afferent and efferent arterioles –> vasoconstriction
How would SNS activation affect on RBF and GFR?
Decrease RBF and GFR
What effect does Angiotensin II have?
Potent vasoconstrictor
Affects both AA and EA
Greater effect on the efferent arteriole
How would Angiotensin II affect RBF and GFR?
Decrease RBF and Inc. GRF