According to myogenic hypothesis of renal autoregulation, the afferent aerioles contract in response to stretch induced by:
**Core Concept:**
The myogenic hypothesis of renal autoregulation states that the afferent arterioles contract in response to stretch induced by changes in intravascular pressure, maintaining renal blood flow and filtration rate despite fluctuations in systemic pressure. The afferent arterioles constrict when blood pressure rises, preventing overload of the nephrons, and dilate when pressure falls, ensuring sufficient perfusion.
**Why the Correct Answer is Right:**
The correct answer, D. Intravascular pressure, is the factor that leads to stretch of the afferent arterioles according to the myogenic hypothesis. This stretch triggers the constriction of afferent arterioles, thus maintaining renal blood flow and filtration rate, vital for effective renal function.
**Why Each Wrong Option is Incorrect:**
A. Efferent arterioles are responsible for vasodilation in response to increased blood flow, not constriction due to pressure changes.
B. Angiotensin II is a key player in the renin-angiotensin-aldosterone system (RAAS) response to low blood pressure, but it does not directly cause afferent arteriole constriction according to the myogenic hypothesis.
C. Nitric oxide (NO) is an important molecule in endothelial function, but it is not directly involved in the myogenic response of afferent arterioles to pressure changes.
**Clinical Pearl / High-Yield Fact:**
The myogenic response is a crucial mechanism ensuring stable renal blood flow and filtration rate, which is essential for maintaining renal function and overall systemic homeostasis. Adequate understanding of this concept is vital for understanding pathophysiology, diagnosing diseases affecting renal autoregulation, and prescribing appropriate treatments.