Question

Explain how all 3 GFR autoregulatory mechanisms combined would respond to a sudden increase in MAP (increase in GFR) to restore GFR. Note: some of these autoregulatory mechanisms might be activated, others inhibited.

Answer 1

Autoregulation of GFR : Autoregulation is an intrinsic ability of an organ to regulate its own blood flow. Inspite of change in mean arterial pressure between 80 mm Hg and 180 mmHg, GFR is maintained nearly constant.

1) Myogenic Mechanism

2) Tubuloglomerular feedback mechanism

3) Gomerulotubular balance

.

1) Myogenic Mechanism - It is intrinsic property of vascular smooth muscle. Increased flow stretch the afferent vessel smooth muscle --> Increased Ca2+ influx --> vasoconstriction --> decresed RBF & GFR

2) Tubuloglomerular feedback - It is feedback regulation of GFR by macula densa cells in Response to change in concentration of sodiun in the tubular lumen.

Macula densa is specialised epithelium in thick Ascending limb of loop of henle. It is stimulated by increased NaCl concentration by Na+K+2Cl- Co-transporter --> release Adenosine --> act on afferent arteriole --> vasoconstriction --> decresed RBF & GFR

3) Glomerulotubular balance -

whenever there is Increased filteration fraction (GFR) --> relatively more Plasma protein in efferent arteriole --> more plasma protein in Vasa recta --> Increased osmotic pressure is vass recta --> Increases reabsorption in PCT.