Chapter 25 Homework AP II

Through the tubuloglomerular feedback mechanism, how would an increase in filtrate NaCl concentration affect afferent arteriole diameter?

--> Afferent arteriole diameter would decrease. High NaCl concentration in the filtrate at the JGA indicates that GFR is too high. By decreasing the diameter of the arteriole delivering blood to the glomerulus, HPg is decreased, resulting in lower GFR.

The myogenic mechanism of renal autoregulation primarily involves smooth muscle in which blood vessels?

--> afferent arterioles By regulating afferent arteriole diameter, the myogenic mechanism affects HPg and therefore GFR. Under normal physiological conditions, this intrinsic control works to maintain GFR despite moderate changes in systemic blood pressure.

Urinary incontinence may occur if a person has ______.

--> an overactive detrusor muscle The detrusor muscle is composed of smooth muscle and surrounds the entire bladder. When it stimulated to contract by the parasympathetic nervous system, it squeezes urine out of the bladder into the urethra, causing urination.

GFR regulation mechanisms primarily affect which of the following?

--> glomerular hydrostatic pressure (HPg) Much like other capillaries in the body, hydrostatic pressure within the glomerular capillaries produces net outward movement of fluid. Unique to glomerular capillaries, HPg is consistently higher than other capillaries (~55 mm Hg), which ensures the one-way movement of fluid and solutes out of the glomerulus under normal conditions.

What does a high concentration of NaCl in the renal tubule at the juxtaglomerular apparatus (JGA) most likely indicate?

--> insufficient NaCl reabsorption due to high GFR After glomerular filtration, NaCl is actively reabsorbed at many locations along the renal tubule. If the filtrate is moving through the tubule quickly, less reabsorption is possible, so more NaCl gets left behind. This means that at the JGA, the NaCl concentration within the filtrate will be high.

Which of the following are mechanisms of intrinsic control of glomerular filtration (renal autoregulation)?

--> myogenic mechanism and tubuloglomerular feedback Both of these mechanisms occur strictly within kidney (i.e., intrinsic controls). The myogenic mechanism is mediated by smooth muscle within the afferent arteriole. In contrast, tubuloglomerular feedback is mediated by macula densa cells of the juxtaglomerular apparatus (JGA).

Granular cells of the juxtaglomerular apparatus (JGA) regulate GFR indirectly through which mechanism?

--> renin-angiotensin mechanism When systemic blood pressure decreases, granular cells release renin which ultimately causes the formation of angiotensin II. Angiotensin II causes widespread vasoconstriction of systemic arterioles and the increase of blood volume due to aldosterone release.

The frequency of cystitis in men is lower than in women because ______.

--> the male urethra is longer than the female urethra and more isolated from contamination by fecal or vaginal bacteria The male urethra is about 6-8 in long while the female urethra is only 1 in long. This shorter distance allows fecal microbes to easily gain access to the bladder of females.

Which of the following best describes glomerular filtration rate (GFR)?

--> the volume of filtrate created by the kidneys per minute. Fluid and small solutes that leave the glomerulus are collectively termed filtrate. Glomerular filtration is driven by glomerular hydrostatic pressure (HPg) and produces ~125 ml of filtrate per minute.

Macula densa cells of the juxtaglomerular apparatus (JGA) regulate GFR through which intrinsic mechanism?

--> tubuloglomerular feedback The JGA is a region of the nephron where the afferent arteriole and its associated tubule are closely apposed. This anatomical arrangement allows macula densa cells to adjust GFR according to the NaCl concentration in filtrate. This is called tubuloglomerular feedback because it allows the contents of the tubules (tubulo-) to affect the glomerular filtration rate.

Since most patients with renal failure produce little or no urine, hemodialysis often involves removal of water from the blood. However, side-effects may develop if too much fluid is removed from the blood. Which of the following is NOT one of the potential side-effects?

--> vasoconstriction of afferent arterioles Vasoconstriction of the afferent arterioles occurs during times of high systemic blood pressure. This reflexive response lowers glomerular blood pressure and helps maintain normal glomerular filtration rates. "Removing excessive fluid gain can make treatment uncomfortable. Patients can experience a sudden drop in blood pressure, which usually occurs toward the end of a dialysis treatment. You may feel nauseated, weak and tired because your body may not be used to having so much fluid removed at once. Some people experience muscle cramping during dialysis when they gain too much fluid weight. Taking out a lot of fluid at one treatment can also leave you feeling dizzy or weak after the treatment."