Tubular Golmerular Feedback + Kidney Function Flashcards
What pressures cause filtration in the bowman’s capsule?
- hydrostatic pressure in capillary PGC + Bowman’s capsule PBC
- oncontic pressure difference between capillary and tubular lumen 𝜋𝐺𝐶
- osmotic pull of albumin in capillary
What of starlings forces has the greatest impact on renal filtration?
Hydrostatic pressure in capillary
How do you calculate net filtration?
NF = hydrostatic pressure of capillary - (hydrostatic pressure of Bowman’s capsule + oncotic pressure difference)
NF = (PGC) – (PBC + 𝜋GC)
Why does the hydrostatic pressure in the glomerulus remain relatively constant?
- to prevent acute tubular necrosis
- if blood flow drops there’s a decrease in glucose + oxygen > ischaemia > necrosis
What happens if blood pressure increases to maintain normal glomerular capillary pressure and decrease GFR?
- constrict afferent arteriole primarily
- dilate efferent arteriole secondary
What happens if blood pressure decreases to maintain normal glomerular capillary pressure and increase GFR?
- constricts efferent arteriole primarily
- dilates afferent arteriole secondary
Describe tubuloglomerular feedback in high blood pressure
- Na+ and Cl- enter macula dense cells in DCT
- water follows > cells swell
- signal sent to juxtaglomeruar cells
- ATP release > converted to adenosine
- adeonsine binds with A1 receptor on afferent arteriole
- vasoconstriction of AA
Role of macula dense cells
Detects changes in Na + Cl
Describe tubuloglomerular feedback when BP is low
- release of prostaglandins > decreases constriction of AE
- renin released by granular cells
- renin converts angiotensinogen to angiotensin I
- ACE converts angiotensin I to angiotensin II
AngII: - vasoconstricts EA
- releases ADH
- stimulates thirst
- aldosterone release > increases Na+ reabsorption from DCT
