Step I RAS question

[Sir Gillies]

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Hi guys,

I am still going through Rx and I came across a question that contradicts what one of the explanations gave in another question. i was wondering whether you could help me to clear this dilemma.

Is it the macula densa in the DCT or the JG cells in the afferent arteriole that detects a drop in Na, leading to the secretion of renin by the JGA?

I think it's the macula densa that detects the drop, but please correct me if I am wrong.
Thanks in advance.

 

[withrye]

You're right.

 

[ZGX]

Hi guys,

I am still going through Rx and I came across a question that contradicts what one of the explanations gave in another question. i was wondering whether you could help me to clear this dilemma.

Is it the macula densa in the DCT or the JG cells in the afferent arteriole that detects a drop in Na, leading to the secretion of renin by the JGA?

I think it's the macula densa that detects the drop, but please correct me if I am wrong.
Thanks in advance.

You are right.

The JGA has 2 parts
JG cells sense afferent
Macula Densa senses DCT

Macula Densa can sense the Na+ in DCT
If the Na+ in DCT is low the Macula Densa tells JG cells to release Renin.

 

[Sir Gillies]

That's a great image! thanks for sharing.

I have also realised that FA says that the afferent arteriole detects the drop in BP. Therefore there are 3 "detectors":
- macula densa - Na
- afferent arteriole - BP
- B1 receptors - sympathetic tone

Thanks again.

 

[Old Style Nanny]

Simply beautiful.