What is the primary driving force (pressure) that produces glomerular filtration?
a. hydrostatic pressure of blood
b. gravity
c. colloid osmotic pressure of blood
answer
a.
-the hydrostatic pressure of blood forces fluid out of the glomerular capillaries.
question
If the osmotic pressure in the glomerular capillaries increased from 28 mm Hg to 35 mm Hg, would net filtration increase or decrease?
a. net filtration would decrease
b. net filtration would increase
c. net filtration would not be altered
answer
a.
-osmotic pressure opposes filtration, increasing osmotic pressure would decrease net filtration.
question
Which of the following best describes glomerular filtration rate (GFR)?
a. the volume of urine leaving the kidneys per minute
b. the volume of filtrate created at the glomerulus per liter of blood flowing through the glomerular capillaries
c. the volume of blood flowing through the glomerular capillaries per minute
d. the volume of filtrate created by the kidneys per minute
answer
d.
-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
question
GFR regulation mechanisms primarily affect which of the following?
a. glomerular hydrostatic pressure (HPg)
b. blood osmotic pressure (OPg)
c. capsular osmotic pressure (OPc)
d. capsular hydrostatic pressure (HPc)
answer
a.
-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.
question
Which of the following are mechanisms of intrinsic control of glomerular filtration (renal autoregulation)?
a. myogenic mechanism and sympathetic nervous system control
b. tubuloglomerular feedback and the renin-angiotensin mechanism
c. sympathetic nervous system control and the renin-angiotensin mechanism
d. myogenic mechanism and tubuloglomerular feedback
answer
d.
-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).
question
Macula densa cells of the juxtaglomerular apparatus (JGA) regulate GFR through which intrinsic mechanism?
a. sympathetic nervous system control
b. myogenic mechanism
c. renin-angiotensin mechanism
d. tubuloglomerular feedback
answer
d.
-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.
question
The myogenic mechanism of renal autoregulation primarily involves smooth muscle in which blood vessels?
a. afferent arterioles
b. efferent arterioles
c. glomeruli
d. systemic arterioles
answer
a.
-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.
question
What does a high concentration of NaCl in the renal tubule at the juxtaglomerular apparatus (JGA) most likely indicate?
a. insufficient NaCl reabsorption due to low GFR
b. excessive NaCl reabsorption due to low GFR
c. excessive NaCl reabsorption due to high GFR
d. insufficient NaCl reabsorption due to high GFR
answer
d.
-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.
question
Through the tubuloglomerular feedback mechanism, how would an increase in filtrate NaCl concentration affect afferent arteriole diameter?
a. Afferent arteriole diameter would increase.
b. Afferent arteriole diameter would decrease.
c. Afferent arteriole diameter would stay about the same.
answer
b.
-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.
question
Granular cells of the juxtaglomerular apparatus (JGA) regulate GFR indirectly through which mechanism?
a. sympathetic nervous system controls
b. myogenic mechanism
c. renin-angiotensin mechanism
d. tubuloglomerular feedback mechanism
answer
c.
-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.
question
What is the function of the macula densa cells of the juxtaglomerular complex (JGC)?
a. The macula densa cells produce filtrate.
b. The macula densa cells sense blood pressure in the afferent arteriole.
c. The macula densa cells pass regulatory signals between the extraglomerular mesangial cells.
d. The macula densa cells monitor the NaCl content of the filtrate entering the distal convoluted tubule.
answer
d.
question
Which capillary bed produces filtrate?
a. glomerulus
b. peritubular capillaries
c. vasa recta
d. juxtaglomerular complex (JGC)
answer
a.
question
What vessel directly feeds into the glomerulus?
a. efferent arteriole
b. cortical radiate artery
c. vasa recta
d. afferent arteriole
answer
d.
question
Which of the following statements about aldosterone is NOT correct?
a. Aldosterone is produced in the adrenal cortex.
b. Aldosterone is stimulated by decreased plasma sodium levels and increased plasma potassium levels.
c. Aldosterone increases the number of passive sodium channels in the luminal membrane of the distal tubule and collecting duct, thus aiding sodium reabsorption.
d. Aldosterone increases sodium reabsorption by increasing the number of Na+-K+ ATPase pumps in the luminal membrane of the proximal tubule.
answer
d.
-aldosterone increases the number of Na+-K+ ATPase pumps in the basolateral membrane of the distal tubules and collecting ducts.
question
Which of the following statements about ADH (antidiuretic hormone) is correct?
a. ADH is synthesized by the adrenal gland and works in the kidney.
b. ADH inserts water channels into the luminal membrane of the proximal tubules.
c. ADH is released by the posterior pituitary gland.
d. ADH would increase urine volume.
answer
c.
-ADH is synthesized in the hypothalamus and stored and released by the posterior pituitary gland.
question
What is the osmolarity of the filtrate at the end of the proximal tubule?
a. hypertonic - 1200 mOsm
b. hypertonic - 600 mOsm
c. isotonic - 300 mOsm
d. hypotonic - 100 mOsm
answer
c.
-the osmolarity of the filtrate would be about 300 mOsm because both solutes and water are reabsorbed in the proximal tubule. As particles are reabsorbed, water follows osmotically.
question
In overhydration, what would be the levels of ADH (high, normal, or low) and what would be the osmolarity of the urine?
a. ADH - low; 600 mOsm (urine)
b. ADH - high; 100 mOsm (urine)
c. ADH - high; 600 mOsm (urine)
d. ADH - low; 100 mOsm (urine)
answer
d.
-in overhydration, ADH would be very low and the cells of the collecting duct would be relatively impermeable to water and urea. Thus, the final urine would be dilute, having an osmolarity of about 100 mOsm.
question
In severe dehydration or blood loss, what would be the levels of ADH and what would be the urine flow rate?
a. ADH - high; low urine flow rate (0.25 ml/min)
b. ADH - low; high urine flow rate (16 ml/min)
c. ADH - high; high urine flow rate (16 ml/min)
d. ADH - low; low urine flow rate (0.25 ml/min)
answer
a.
-ADH would be high, causing a large percentage of the water to be reabsorbed. Therefore, the urine flow rate would be low.
question
Which of the following is the volume of filtrate formed each minute by all of the glomeruli of the kidneys?
a. net filtration pressure (NFP)
b. hydrostatic pressure in glomerular capillaries (HPgc)
c. glomerular filtration rate (GFR)
d. hydrostatic pressure in the capsular space (HPcs)
answer
c.
question
What hormone promotes active tubular secretion of potassium ions in the late distal convoluted tubule (DCT) and collecting ducts?
a. atrial natriuretic peptide (ANP)
b. aldosterone
c. antidiuretic hormone (ADH)
d. parathyroid hormone (PTH)
answer
b.
question
In what part of the renal tubule are aquaporins scarce or absent so that water CANNOT be reabsorbed?
a. proximal convoluted tubule (PCT)
b. ascending limb of the nephron loop
c. descending limb of the nephron loop
d. collecting duct
answer
b.
question
In what part of the renal tubule does parathyroid hormone (PTH) promote the reabsorption of calcium ions?
a. collecting duct
b. proximal convoluted tubule (PCT)
c. descending limb of the nephron loop
d. distal convoluted tubule (DCT)
answer
d.
question
Which of the following promotes the formation of dilute urine?
a. increased number of aquaporins present in the collecting duct
b. decreased osmolality of extracellular fluids
c. increased osmolality of extracellular fluids
d. large amounts of antidiuretic hormone (ADH) released from the posterior pituitary
answer
b.
question
Which statement best describes the effect diuretics have?
a. Diuretics increase water reabsorption as a way to decrease the osmolality of the extracellular fluids.
b. Diuretics increase urinary output.
c. Diuretics promote sodium reabsorption and enhance the obligatory water reabsorption that follows.
d. Diuretics promote the formation of the medullary gradient by acting on the ascending limb of the nephron loop.
answer
b.
question
Where does antidiuretic hormone (ADH) exert its effects to promote water reabsorption?
a. descending limb of the nephron loop
b. collecting duct
c. ascending limb of the nephron loop
d. distal convoluted tubule (DCT)
answer
b.
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