What is the effect of increased sympathetic tone on the kidneys and ureters?

What is the effect of increased sympathetic tone on the kidneys and ureters?

• A. Decreases GFR, decreases urine output, and decreases ureteral peristalsis (anti-SLDGE)
• B. Increases GFR and urine output
• C. No change to kidney function
• D. Increases ureteral peristalsis

Answer: (A)

Increased sympathetic tone to the kidneys lowers renal blood flow and filtration pressure. Norepinephrine acts on α1 receptors on the afferent arterioles, causing vasoconstriction that reduces GFR and, as a result, decreases urine production. There is also β1-mediated renin release which activates the renin-angiotensin system, but the net acute effect of sympathetic activation is a drop in GFR and urine output. For the ureters, sympathetic stimulation inhibits smooth muscle contractions, slowing peristalsis and reducing the transport of urine from the kidneys to the bladder. So the combined effect is decreased GFR, decreased urine output, and decreased ureteral peristalsis.

Increased sympathetic tone to the kidneys lowers renal blood flow and filtration pressure. Norepinephrine acts on α1 receptors on the afferent arterioles, causing vasoconstriction that reduces GFR and, as a result, decreases urine production. There is also β1-mediated renin release which activates the renin-angiotensin system, but the net acute effect of sympathetic activation is a drop in GFR and urine output. For the ureters, sympathetic stimulation inhibits smooth muscle contractions, slowing peristalsis and reducing the transport of urine from the kidneys to the bladder. So the combined effect is decreased GFR, decreased urine output, and decreased ureteral peristalsis.