UNIT 4: Urinary System (Mylab and Mastering)
Through the tubuloglomerular feedback mechanism, how would an increase in filtrate NaCI concentration affect afferent arteriole diameter?
Afferent arteriole diameter would decrease. (High NaCI concentration in the filtrate at the JGA indicates that GF is too high. By decreasing the diameter of the arteriole delivering blood to the glomerulus. Hs is decreased, resulting in lower GFR.)
ADH causes the reabsorption of ________ in the kidney tubule.
Water (ADH (antidiuretic hormone) causes aquaporins to be inserted into the cell membranes of the collecting duct cells, facilitating the reabsorption of water from the filtrate, back into the blood.)
During reabsorption of water in the proximal convoluted tubule, what causes water to diffuse from the lumen into the interstitial space?
an increase in the osmolarity of the interstitium (the increase in osmolarity causes the water to move into the interstitium.)
When filtrate flow through the renal tubule increases, reabsorption of sodium chloride by the tubule _________
decreases
Alcohol acts as a diuretic because it ________.
inhibits the release of ADH
You've counseled Mr. Boulard about how to prevent recurrence of his hypokalemia. Which of the statements he makes indicates a need for further instruction? A. "I guess I need to come in regularly and have potassium levels checked." B. "There's lots of potassium in regular table salt, so I'll just use more." C. "There's lots of potassium in fruits and vegetables, so I'll eat more bananas." D. "Maybe I should take a potassium supplement."
"There's lots of potassium in regular table salt, so I'll just use more." (Table salt is NaCl, not KCl. So ingesting it will not help prevent hypokalemia.)
For each of the following, indicate whether it would cause an increase in aldosterone secretion, a decrease in aldosterone secretion, or no change in aldosterone secretion.
(ADH and aldosterone allow the reabsorption of water (via ADH) and sodium (via aldosterone) from the filtrate. These two hormones allow "fine-tuning" of the filtrate water, electrolyte, and acid-base composition in order to meet the ever changing needs of the body.)
The kidney uses three hormones to adjust the concentration and volume of the urine. These hormones function by changing the permeabilities of the late distal convoluted tubule and collecting duct. Complete the following statements about these hormones and their effect on urine output.
(ADH, aldosterone, and ANP provide a way for the body to "fine-tune" urine production and body water conservation to maintain homeostasis amid changing environmental conditions.)
Identify parts of the nephron and vasa recta involved in concentrating urine.
(In both the nephron loop and the vasa recta, the fluid moves in opposite directions in the same tube, due to a hairpin turn at the bottom of the tube. This pattern of fluid flow allows an osmotic gradient to be formed and maintained in the kidney medulla in order to concentrate the urine.)
For each of the following locations, tell whether NaCl will enter the interstitial fluid, leave the interstitial fluid and enter the filtrate or blood, or not move (is impermeable to solutes).
(The differing permeabilities of the nephron loop allow salt to leave the filtrate in the ascending limb, but prevent its movement in the descending limb to ensure a high enough solute concentration in the filtrate to generate an osmotic gradient to drive water reabsorption.)
For each of the following locations, tell whether water will enter the interstitial fluid, leave the interstitial fluid and enter the filtrate or blood, or not move (impermeable to water).
(The differing permeabilities of the nephron loop create an osmotic gradient in the kidney medulla that draws water out of the filtrate. The vasa recta exchanges NaCl and water with the interstitial fluid in order to maintain this osmotic gradient.)
Determine whether each of the following scenarios will lead to urine production with a high volume and low concentration or urine production with a low volume and a high concentration.
(When body fluid compartments are low in fluid, the kidney works to excrete the body's wastes in the smallest volume of water possible. If too much water is present, solutes in the body can become too diluted, so the kidney produces a larger volume of dilute urine in order to restore proper hydration.)
If one says that the clearance value of glucose is zero, what does this mean?
100% of glucose is reabsorbed.
Calculate the net filtration pressure if blood pressure in the glomerulus is unusually high, around 68 millimeters of mercury (mm Hg). Assume the colloid osmotic pressure and capsular hydrostatic pressure are normal.
23 mm Hg (Net filtration pressure is calculated by subtracting the inward pressures from the outward pressures: (HPgc) − (HPcs + OPgc).)
Calculate the net filtration pressure if capillary hydrostatic pressure is 60 mm Hg, capillary osmotic pressure is 25 mm Hg, and capsular hydrostatic pressure is 10 mm Hg.
25mm Hg (60 - (25 + 10) = 25 mm Hg. The two pressures that oppose filtration must be subtracted from the force favoring filtration.)
Which of the following is the best explanation for why the cells of the proximal convoluted tubule (PCT) contain so many mitochondria? A. A great deal of active transport takes place in the PCT. B. Cells of the PCT go through a great deal of mitosis. C. This provides the energy needed to fight kidney infection. D. Contraction of the PCT moves filtrate through the tubule.
A great deal of active transport takes place in the PCT
In severe dehydration or blood loss, would ADH levels be high or low, and would urine production be high or low?
ADH - high; urine production - low (ADH (antidiuretic hormone) causes aquaporins to be inserted into the cell membranes of the collecting duct cells, facilitating the reabsorption of water from the filtrate, back into the blood. By doing this, ADH helps a dehydrated individual to minimize water loss through urine, and maximize water reabsorption to help rehydrate cells.)
What hormone promotes active tubular secretion of potassium ions and reabsorption of sodium ions in the distal convoluted tubule (DCT) and collecting ducts?
Aldosterone Aldosterone from the adrenal cortex promotes active tubular secretion of potassium ions in the late distal convoluted tubule (DCT) and collecting ducts. It is secreted in indirect response to actions of the juxtaglomerular apparatus.
Lisa suffers from kidney stones. One small stone manages to get lodged in the ascending limb of the nephron loop of one of her nephrons. Predict what would happen to the amount of filtrate produced over time by this particular nephron.
Decrease in filtrate production due to an increase in hydrostatic pressure in the capsular space
Which of the following statements best describes the difference between the intrinsic and extrinsic controls of the kidney? A. Intrinsic controls raise blood pressure while extrinsic controls lower blood pressure. B. Extrinsic controls have the greatest effect on systemic blood pressure while intrinsic controls have a greater effect on GFR. C. Extrinsic controls will reduce blood plasma volume while intrinsic controls will increase blood plasma volumes. D. Extrinsic and intrinsic controls work in nearly opposite ways.
Extrinsic controls have the greatest effect on systemic blood pressure while intrinsic controls have a greater effect on GFR.
True or False: The myogenic mechanism reflects the tendency of vascular smooth muscle to stretch.
False
True or False: Capsular hydrostatic pressure is the chief force pushing water and solutes out of the blood and across the filtration membrane.
False (When the forces directed out of the capillary (glomerulus) exceed the forces directed into the capillary, net filtration pressure is positive, and filtration occurs. Glomerular hydrostatic (blood) pressure is the chief (outward directed) force pushing water and solutes out of the blood and across the filtration membrane.)
When the macula densa detects an increase in NaCl concentration in the renal filtrate, what happens to the glomerular filtration rate (GFR)?
GFR decreases
If blood pressure drops very low (MAP is below 80mmHg) renin enzyme will be secreted by granular cells. Which of the following is NOT likely to occur? A. Net filtration pressure (NFP) will decrease. B. Kidney perfusion will increase. C. Glomerular filtration rate (GFR) will decrease. D. Blood plasma and extracellular fluids volume will increase.
Kidney perfusion will increase.
Which of the following transporters in the luminal membrane results in secretion? A. glucose carrier transporter B. Na+-H+ countertransport C. Na+-glucose cotransporter D. potassium ion channel
Na+-H+ countertransport (because this is a countertransporter, Na+ is transported into the cell and H+ is transported out of the cell into the lumen.)
If the osmotic pressure in the glomerular capillaries increased from 28 mmHg to 35 mmHg due to dehydration, would net filtration increase or decrease?
Net filtration would decrease
What would happen if the capsular hydrostatic pressure were increased above normal? A. Net filtration would increase above normal. B. Capsular osmotic pressure would compensate so that filtration would not change. C. Filtration would increase in proportion to the increase in capsular pressure. D. Net filtration would decrease.
Net filtration would decrease.
If the diameter of the afferent arterioles leading to the glomerulus decreases (vasoconstriction), which of the following is NOT likely to occur? A. Systemic blood pressure will decrease. B. Glomerular filtration rate will decrease. C. Net filtration pressure will decrease. D. Urine output will decrease.
Systemic blood pressure will decrease.
If the diameter of the afferent arterioles leading to the glomerulus increases (vasodilation), which of the following is NOT likely to occur? A. Net filtration pressure will increase. B. Urine output will increase. C. Systemic blood pressure will go up. D. Glomerular filtration rate will increase.
Systemic blood pressure will go up.
If the diameter of the efferent arterioles leading away from the glomerulus decreases (vasoconstriction), which of the following is NOT likely to occur? A. Urine output will increase. B. Net filtration pressure will increase. C. Glomerular filtration rate will increase. D. Systemic blood pressure will go up.
Systemic blood pressure will go up.
Which of the following is incorrect? A. The concentration of urine is lower when urine volume is reduced. B. Urine concentration and volume are determined by countercurrent mechanisms C. The kidneys produce a large volume of dilute urine when overhydrated. D. The kidneys produce a small volume of concentrated urine when dehydrated.
The concentration of urine is lower when urine volume is reduced.
Mr. Boulard's blood pressure is quite high. How would this affect his nephron function? Choose the statement below that is most accurate. A. The kidneys normally increase their rate of reabsorption when blood pressure increases. B. The kidneys normally increase both their rate of filtration and reabsorption when blood pressure increases. C. The kidneys release more renin when blood pressure increases, activating the renin-angiotensin-aldosterone pathway. D. The heart releases atrial natriuretic peptide that reduces sodium reabsorption at the kidney when blood pressure increases.
The heart releases atrial natriuretic peptide that reduces sodium reabsorption at the kidney when blood pressure increases. (Atrial natriuretic peptide is released by the heart in response to high blood pressure. It targets the nephron where it reduces the reabsorption of sodium, which leads to less water being reabsorbed. More water is lost in urine, reducing the blood volume and blood pressure.)
Which of the following is NOT one of the things that must happen for micturition to occur? A. The pontine storage center must be activated. B. The internal urethral sphincter must open. C. The external urethral sphincter must open. D. The detrusor muscle must contract.
The pontine storage center must be activated. (The pons has two centers that participate in control of micturition. The pontine storage center inhibits micturition, whereas the pontine micturition center promotes this reflex. Thus, it is the pontine center that would need to be activated for micturition to occur.)
Hydrostatic pressure is the primary driving force of plasma through the filtration membrane into the capsular space. All but one of the following statements reflects why hydrostatic pressure is so high in the glomerular capillaries. Select the one statement that does NOT explain the high pressure within the glomerular capillaries. A. The volume of plasma in the efferent arteriole is higher when compared to the afferent arteriole. B. The flow of blood is reduced as blood reaches the efferent arteriole. C. The efferent arteriole has higher resistance to blood flow than the afferent arteriole. D. The diameter of the efferent arteriole is smaller than the afferent arteriole.
The volume of plasma in the efferent arteriole is higher when compared to the afferent arteriole
What is the best explanation for the microvilli on the apical surface of the proximal convoluted tubule (PCT)? A. They increase the amount of surface area that comes in contact with the blood's plasma to help actively excrete toxins. B. They increase the surface area and allow for a greater volume of filtrate components to be reabsorbed. C. Their movements propel the filtrate through the tubules. D. They hold on to enzymes that cleanse the filtrate before reabsorption.
They increase the surface area and allow for a greater volume of filtrate components to be reabsorbed.
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
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.)
Which of the following hormones acting on the collecting duct is most responsible for retaining sodium ions in the blood? A. atrial natriuretic peptide B. antidiuretic hormone C. aldosterone D. parathyroid hormone
aldosterone
Which of the choices below are the most important hormone regulators of electrolyte reabsorption and secretion? A. angiotensin I and atrial natriuretic peptide B. angiotensin II and ADH C. angiotensin II and aldosterone D.angiotensin I and epinephrine
angiotensin II and aldosterone
Reabsorption of sodium in the medulla by active transport is undertaken by cells that compose which of the following? A. ascending nephron loop B. proximal convoluted tubule C. vasa recta D. descending nephron loop
ascending nephron loop (Active transport of sodium by the cells of the ascending loop creates the high osmolality of the interstitial fluids in the medulla.)
Which of the following substances is not normally found in filtrate? A. blood cells and large particles B. nitrogenous waste particles, such as urea C. ions, such as sodium and potassium D. water and small solutes
blood cells and large particles (both blood cells and large particles, such as proteins, are not allowed to filter through a healthy glomerular membrane.)
The kidneys are stimulated to produce renin ________.
by a decrease in the blood pressure
Which of the choices below is NOT a method by which the cells of the renal tubules can raise blood pH? A. by producing new bicarbonate ions B. by secreting sodium ions C. by reabsorbing filtered bicarbonate ions D. by secreting hydrogen ions into the filtrate
by secreting sodium ions
What is the effect of antidiuretic hormone on the cells of the collecting duct?
causes aquaporins to be inserted into the apical membranes
The function of angiotensin II is to ________
constrict arterioles and increase blood pressure
Which of the following is NOT reabsorbed by the proximal convoluted tubule? A. creatinine B. glucose C. K+ D. Na+
creatinine
The presence of protein in the urine indicates which of the following? A. high levels of transcription and translation by the bodies tissues B. too much protein in the diet C. damage to the renal tubules D. damage to the filtration membrane
damage to the filtration membrane
Which of the following would NOT inhibit micturition? A. increase in sympathetic activity B. increase in somatic muscle activity C. decrease in parasympathetic activity D. detrusor contraction
detrusor contraction (Contraction of the detrusor muscle is required to empty the bladder during micturition. The pontine micturition center promotes this action by inhibiting the sympathetic neurons, and by exciting the parasympathetic neurons, that innervate the bladder)
In what part of the renal tubule does parathyroid hormone (PTH) promote the reabsorption of calcium ions?
distal convoluted tubule (DCT) (Parathyroid hormone (PTH) promotes the reabsorption of calcium ions in the distal convoluted tubule (DCT).)
The glomerular capsular space contains ________.
filtrate
Which of the choices below is a function of the nephron loop? A. absorb electrolytes actively and water by osmosis in the same segments B. absorb water and electrolytes into the tubular network C. form a large volume of very dilute urine or a small volume of very concentrated urine D. form a large volume of very concentrated urine or a small volume of very dilute urine
form a large volume of very dilute urine or a small volume of very concentrated urine
Glomerular filtration rate can be controlled by manipulating one major variable, which is ________. A. glomerular hydrostatic pressure B. systemic blood pressure C. activation of sympathetic nerve fibers D. the renin-angiotensin-aldosterone mechanism
glomerular hydrostatic pressure
The factor that promotes filtrate formation at the glomerulus is the ________.
glomerular hydrostatic pressure
GFR regulation mechanisms primarily affect which of the following? A. glomerular hydrostatic pressure (HPg) B. blood osmotic pressure (OPg) C. capsular hydrostatic pressure (HPc) D. capsular osmotic pressure (OPc)
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.)
The chief force pushing water and solutes out of the blood across the filtration membrane is ________.
glomerular hydrostatic pressure (glomerular blood pressure)
Your patient's urinalysis shows a large amount of protein in the urine. This suggests a problem in the ____________
glomerulus (If the glomerular capillary is damaged, large molecules such as proteins can pass through the filtration membrane and appear in the urine.)
Which of these should not normally appear in urine? A. creatine B. sodium C. urea D. glucose
glucose (Glucose would normally be completely reabsorbed during urine formation and should not be in a urine sample.)
Which cells of the juxtaglomerular apparatus secrete renin? A. macula densa cells B. glomerular mesangial cells C. granular cells D. extraglomerular mesangial cells
granular cells (Granular cells are mechanoreceptors that sense blood pressure in the afferent arterioles. They secrete renin when the blood pressure drops and are an important part of the renin-angiotensin-aldosterone regulatory pathway.)
What is the most direct function of the juxtaglomerular apparatus?
help regulate blood pressure and the rate of blood filtration by the kidneys
What is the chief force pushing water and solutes out of the blood and across the filtration membrane of the glomerulus?
hydrostatic pressure in glomerular capillaries (HPgc) (While diffusion rates are affected more by osmotic differences and concentration gradients, hydrostatic pressure in glomerular capillaries (HPgc) is the chief method of forcing water and solutes by filtration.)
What is the primary driving force (pressure) that produces glomerular filtration? A. colloid osmotic pressure of blood B. gravity C. hydrostatic pressure of blood (blood pressure)
hydrostatic pressure of blood (blood pressure) (the hydrostatic pressure of blood forces fluid out of the glomerular capillaries.)
Filtrate flow through the renal tubule increases when glomerular filtration rate________
increases
When filtrate flow through the renal tubule increases, the concentration of sodium chloride remaining in the filtrate _______
increases
Cells and transport proteins are physically prevented from passing through the filtration membrane. This has the following effect on filtration: A. increasing osmotic pressure in the glomerular capillaries that reduces the amount of filtration B. increased osmotic pressure in the filtrate that draws plasma through the membrane C. decreased osmotic pressure in the filtrate that increases the amount of filtration D. neutral change in osmotic pressure with no effect on filtration
increasing osmotic pressure in the glomerular capillaries that reduces the amount of filtration
What does a high concentration of NaCI in the renal tubule at the juxtaglomerular apparatus (JGA) most likely indicate?
insufficient NaCI reabsorption due to high GFR (After glomerular filtration, NaCI 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 NaCI gets left behind. This means that at the JGA, the NaCI concentration within the filtrate will be high.)
Bulk flow of nutrients, ions and water into the peritubular capillaries is the result of all of the following except one. Select the answer below that does NOT describe a cause of bulk flow of fluids into the peritubular capillaries. A. leaky tight junctions of peritubular capillary's endothelium B. higher osmotic pressure in the peritubular capillary C. increased resistance to blood flow at the efferent arteriole D. lower hydrostatic pressure in the peritubular capillary
leaky tight junctions of peritubular capillary's endothelium
What is the function of the macula densa cells of the juxtaglomerular complex (JGC)?
monitoring the NaCl content of the filtrate (The macula densa cells monitor the NaCl content of the filtrate entering the distal convoluted tubule.)
Which of the following are mechanisms of intrinsic control of glomerular filtration (renal autoregulation)? A. sympathetic nervous system control and the renin-angiotensin mechanism B. myogenic mechanism and sympathetic nervous system control C. myogenic mechanism and tubuloglomerular feedback D. tubuloglomerular feedback and the renin-angiotensin mechanism
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).)
The mechanism that establishes the medullary osmotic gradient depends most on the permeability properties of the ________.
nephron loop
Which structure is INCORRECTLY matched with a function? A. distal convoluted tubule: secretion of K+ B. proximal convoluted tubule: reabsorption of water C. nephron loop: reabsorption of urea D. glomerulus: filtration of plasma
nephron loop: reabsorption of urea (Urea in the medullary interstitial fluid is secreted into the ascending thin limb of the nephron loop. This is followed by the reabsorption of urea in the collecting duct, which completes the process of urea recycling.)
Which pressure accounts for the other three? A. capsular hydrostatic pressure B. net filtration pressure C. glomerular hydrostatic pressure D. blood colloid osmotic pressure
net filtration pressure (Net filtration pressure is a combination of glomerular hydrostatic pressure minus capsular hydrostatic pressure and colloidal osmotic pressure.)
If the osmotic pressure in the glomerular capillaries increased from 28 mm Hg to 35 mm Hg, would net filtration increase or decrease?
net filtration would decrease (because osmotic pressure opposes filtration, increasing osmotic pressure would decrease net filtration.)
What is the limiting factor for the reabsorption of most actively transported solutes in the proximal tubule? A. number of transport carriers in the basolateral membrane B. number of sodium-potassium ATPase pumps in the basolateral membrane C. number of transport carriers in the luminal membrane
number of transport carriers in the luminal membrane (the number of carriers is the rate-limiting factor. For example, in Diabetes Mellitus, plasma glucose levels are very high, and the sodium-glucose transporter cannot transport (reabsorb) all the glucose passing through the proximal tubule. Glucose is therefore found in the urine.)
Which substance would be found in higher concentration if the membrane were damaged? A. glucose B. chloride C. creatinine D. protein
protein (large proteins are not normally filtered by a healthy glomerular membrane.)
Which of the following is NOT a function of the kidneys? A. carry out gluconeogenesis during prolonged fasting B. regulate body fluid by controlling excretion from sweat glands C. regulate blood volume and osmolality, and maintain acid-base balance D. metabolize vitamin D to its active form
regulate body fluid by controlling excretion from sweat glands (The kidneys have no control over excretion of fluid from the sweat glands. Sweating is controlled by the sympathetic nervous system.)
Which of the following is the primary function of the juxtaglomerular complex? A. releases chemical signals that regulate the rate of filtrate formation B. a system that protects the nephron from some chemicals found in blood C. concentrating urine D. reabsorption of Na+ and other ions
releases chemical signals that regulate the rate of filtrate formation (The macula densa cells and granular cells of the juxtaglomerular complex (JGC) release, respectively, vasoactive chemicals and renin. These chemical messengers lead to changes in vasomotor activity and Na+ reabsorption that affect the rate of filtrate formation and systemic blood pressure.)
When filtrate flow through the renal tubule increases, the macula densa responds by __________ vasoconstrictors
releasing
Granular cells of the juxtaglomerular apparatus (JGA) regulate GFR indirectly through which mechanism? A. myogenic mechanism B. tubuloglomerular feedback mechanism C. sympathetic nervous system controls D. renin-angiotensin 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.)
Reabsorption of high levels of glucose and amino acids in the filtrate is accomplished by ________.
secondary active transport
An important physical characteristic of urine is its specific gravity or density, which is ________. A. the same as water B. much higher than water C. less than water D. slightly higher than water
slightly higher than water
Approximately 80% of the energy used for active transport is devoted to the reabsorption of __________.
sodium (About 80% of the energy used for active transport is devoted to reabsorbing sodium. Na+ is actively transported out of the tubule cells by primary active transport—a Na+-K+ ATPase pump in the basolateral membranes.)
Aldosterone causes the reabsorption of ________ in the kidney tubule.
sodium (The secretion of aldosterone stimulates the synthesis and retention of more sodium channels and sodium-potassium pumps in the kidney tubule, therefore enhancing sodium reabsorption.)
The active transport of which ion out of proximal convoluted tubule cells causes the reabsorption of both water and solutes?
sodium (the active transport of sodium out of the cell, across the basolateral membrane into the interstitium, provides the driving force for reabsorption of both water and solutes.)
The fatty tissue surrounding the kidneys is important because it ________.
stabilizes the position of the kidneys by holding them in their normal position
The decreased intracellular concentration of sodium in tubular cells during active transport is caused by which of the following mechanisms? A. passive sodium channels B. the sodium-potassium ATPase pump in the basolateral membrane C. sodium-glucose cotransporter D. the sodium-potassium ATPase pump in the luminal membrane
the sodium-potassium ATPase pump in the basolateral membrane (this pump moves sodium out of the cell into the interstitium, thus decreasing intracellular sodium)
Which of the following acts as the trigger for the initiation of micturition (voiding)? A. motor neurons B. the stretching of the bladder wall C. the sympathetic efferents D. the pressure of the fluid in the bladder
the stretching of the bladder wall
Which of the following best describes glomerular filtration rate (GFR)? A. the volume of filtrate created by the kidneys per minute B. the volume of blood flowing through the glomerular capillaries per minute C. the volume of urine leaving the kidneys per minute D. the volume of filtrate created at the glomerulus per liter of blood flowing through the glomerular capillaries
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.)
Most solutes that are reabsorbed in the proximal convoluted tubule use which of the following pathways? A.paracellular B. transcellular
transcellular (most substances are reabsorbed first through the luminal and then through the basolateral membranes of the proximal convoluted tubule.)
Macula densa cells of the juxtaglomerular apparatus (JGA) regulate GFR through which intrinsic mechanism? A.tubuloglomerular feedback B. sympathetic nervous system control C. renin-angiotensin mechanism D. myogenic 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.)
When filtrate flow through the renal tubule increases, the afferent arteriole responds by ____________
vasoconstricting
Which of the following is NOT a cause of anuria? A. renal failure B. obstruction in the urethra C. vasodilation of afferent arterioles D. heart failure
vasodilation of afferent arterioles (Vasodilation of the afferent arterioles occurs during times of low systemic blood pressure. This reflexive response raises glomerular blood pressure and helps maintain normal glomerular filtration rates. Anuria is an abnormally low urine output (<50 ml/day).)
