Question

Kidney responds to shock by

• A. Decreases renal blood flow
• B. Increases afferent arteriole resistance
• C. GFR remains unaltered
• D. Perfusion of kidney increases

Answer 1

The Correct Option is B

In response to shock, the body's physiological mechanisms aim to preserve blood flow to vital organs and maintain blood pressure. The kidney plays a crucial role in this response:

1. Decreases renal blood flow: Shock leads to a decrease in overall blood volume and pressure. The body responds by redirecting blood away from less vital organs like kidneys to essential organs, thus decreasing renal blood flow.
2. Increases afferent arteriole resistance: To reduce renal blood flow, there is an increase in the resistance of the afferent arterioles. This response is mediated by vasoconstrictor hormones like norepinephrine, angiotensin II, and endothelin, which cause the arterioles supplying the glomeruli to constrict, thus maintaining systemic blood pressure.
3. GFR remains unaltered: Under normal conditions, renal autoregulation helps maintain the Glomerular Filtration Rate (GFR) despite changes in blood pressure. However, in shock, autoregulation may be overwhelmed, potentially altering the GFR.
4. Perfusion of the kidney increases: This is incorrect in the context of shock as the body redirects blood away from the kidneys to prioritize critical organs like the brain and heart.

Summary: The kidney responds to shock by increasing the resistance of the afferent arterioles (correct answer), thereby reducing renal blood flow to help maintain systemic blood pressure.