11 Renal Flashcards
What is GFR?
The amount of a substance secreted into the urine/plasma conc. of the substance
What regulates GFR?
Regulated by two pathways: Intrinsic & extrinsic
What is the mean arterial pressure for the glomerulus?
70-100 mmHg to ensure safe organ perfusion
What is the equation for mean arterial blood pressure?
MAP= DP –
[1/3(SP-DP)]
What is the net pressure of the glomerulus?
10 mmHg
What are the two parts of the intrinsic pathway?
Myogenic response & tubulogloerular feedback
What is the myogenic response?
- blood pressure increases
- afferent artery stretches due to high blood flow
- activates stretch-activated sodium intracellular influx
- causes vasoconstriction of AFFERENT arterioles
What is the benefit of the intrinsic pathway?
The vasoconstriction opposes the high perfusion and reduce the damage of the glomerular capillaries which could lead to kidney disease
What is the tubuloglomerular feedback?
- increase perfusion causes increase salt perfusion (NaCl)
- NaCl is perfused into the macula densa cells through NKCC2 transporters
- once at a high intracellular conc. ATP is released from pannexin channels
- release ATP –> AMP –> adenosine
- adenosine binds to A1 receptor of extraglomerular mesangial cells
- calcium is then released to smooth muscles
- vasodialation
What are the routes of the extrinsic pathway?
Neural and hormonal
Describe the neural extrinsic pathway
- blood volume reduced
- blood perfusion reduction sensed by juxtaglomerular cells
- sympathetic nervous system activated to release NA
- constriction of afferent and efferent arterioles
- enhancing perfusion, reducing filtration and fluid loss
When GFR drops, how does the hormonal extrinsic pathway compensate?
- macula densa cells are stimulated
- they stimulate granular cells of the juxtaglomerular complex
- they release renin that activate RAAS
- vasoconstriction and reduction of blood flow occurs
- enhances perfusion
