The kidneys are innervated by sympathetic nerves of the autonomic nervous system. Sympathetic nervous activity decreases blood flow to the kidney, making more blood available to other areas of the body during times of stress. The arteriolar myogenic mechanism maintains a steady blood flow by causing arteriolar smooth muscle to contract when blood pressure increases and causing it to relax when blood pressure decreases. Tubuloglomerular feedback involves paracrine signaling at the JGA to cause vasoconstriction or vasodilation to maintain a steady rate of blood flow.
myogenic mechanism
mechanism by which smooth muscle responds to stretch by contracting; an increase in blood pressure causes vasoconstriction and a decrease in blood pressure causes vasodilation so that blood flow downstream remains steady
tubuloglomerular feedback
feedback mechanism involving the JGA; macula densa cells monitor Na+ concentration in the terminal portion of the ascending loop of Henle and act to cause vasoconstriction or vasodilation of afferent and efferent arterioles to alter GFR
1. Vasodilation of blood vessels to the kidneys is due to ________.
A) more frequent action potentials
B) less frequent action potentials
B
2. When blood pressure increases, blood vessels supplying the kidney will ________ to mount a steady rate of filtration.
A) contract
B) relax
A
3. Which of these three paracrine chemicals cause vasodilation?
A) ATP
B) adenosine
C) nitric oxide
C
1. Explain what happens to Na+ concentration in the nephron when GFR increases.
Sodium concentration in the filtrate increases when GFR increases; it will decrease when GFR decreases.
2. If you want the kidney to excrete more Na+ in the urine, what do you want the blood flow to do?
To excrete more Na+ in the urine, increase the flow rate.