Renal blood flow and GFR remain nearly constant when mean arterial pressure varies between 80 and 180 mmHg. Besides tubuloglomerular feedback, which intrinsic mechanism produces this autoregulation?

• A Baroreceptor reflexes adjusting sympathetic tone to the juxtaglomerular apparatus
• B Angiotensin II mediated selective constriction of the efferent arteriole across this pressure range
• C Pressure-induced stretch of the afferent arteriole triggering vascular smooth muscle contraction ✓
• D Pressure natriuresis reducing plasma volume within seconds

Explanation

The myogenic mechanism operates independently of neural input: raised transmural pressure stretches afferent arteriolar smooth muscle, depolarizing it and opening stretch activated calcium channels, which causes contraction and increases resistance, holding flow constant. This is an entirely local, preglomerular response. Angiotensin II modulates autoregulation but is not required for the intrinsic phenomenon, and baroreceptor reflexes act systemically rather than intrinsically within the kidney. Pressure natriuresis adjusts long term sodium balance and cannot stabilize GFR within seconds.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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