Bio Confusing qsn

[ammarm]

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How can the macula densa cells of the distal convoluted tubule increase the hydrostatic pressure in the glomerulus when the filtrate volume is low?

I get confused.. is it by increasing the resistance to the afferent arteriole or efferent arteriole?? can someone please clarify this for me?

 

[PooyaH]

Macula densa causes the release of renin when the concentration of Na is low and renin/angiotensin causes an increases in blood pressure and eventually the hydrostatic pressure of the glomerulus.

Also, when you increase the blood flow of the afferent arteries by decreasing the resistance, the hydrostatic pressure of the glomerulus increases.

 

[PooyaH]

Here's how you should look at it:

1. When you increase the resistance of the afferent artery only, glomerular-capillary hydrostatic pressure (PGC) decreases and as a result the total renal blood flow (RBF) decreases.

2. When you increases the resistance of the efferent artery only, PGC increases and as a result the total RBF decreases.

3. when you increase the resistance of both afferent and efferent arteries, PGC stays normal and as a result the total RBF decreases (by a lot more than the other 2 scenarios)

If you get confused by reading it, just draw it out, it'll make sense.