Anatomy and Phys II Exam 4 Urinary System
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Free Anatomy and Phys II Exam 4 Urinary System Questions
What is the effect of antidiuretic hormone on the cells of the collecting duct?
- Triggers synthesis of more sodium channels in the collecting duct apical membranes
- Triggers synthesis of more potassium channels in the collecting duct apical membranes
- Causes aquaporins to be inserted into the collecting duct apical membranes
- Inhibits sodium reabsorption through the collecting duct apical membranes
Explanation
Explanation:
Correct Answer: (C) Causes aquaporins to be inserted into the collecting duct apical membranes
ADH (antidiuretic hormone/vasopressin) binds to V2 receptors on collecting duct cells, triggering a cAMP-mediated signaling cascade that causes aquaporin-2 water channels to be inserted into the apical membranes of the collecting duct cells. This dramatically increases the permeability of the collecting duct to water, allowing water to be reabsorbed by osmosis into the hypertonic medullary interstitium, producing concentrated urine.
Why Other Options are Incorrect:
- A. Triggers synthesis of more sodium channels — Sodium channel regulation in the collecting duct is primarily controlled by aldosterone, not ADH.
- B. Triggers synthesis of more potassium channels — Potassium channel regulation is associated with aldosterone's effects on principal cells, not ADH.
- D. Inhibits sodium reabsorption — ADH does not inhibit sodium reabsorption; its primary action is on water permeability through aquaporin insertion.
The chief force pushing water and solutes out of the blood across the filtration membrane is _______.
- The ionic electrochemical gradient
- Glomerular hydrostatic pressure (glomerular blood pressure)
- Protein-regulated diffusion
- The size of the pores in the basement membrane of the capillaries
Explanation
Explanation:
Correct Answer: (B) Glomerular hydrostatic pressure (glomerular blood pressure)
Glomerular hydrostatic pressure is the primary driving force for filtration at the glomerulus. The high blood pressure within the glomerular capillaries — significantly higher than in other capillary beds — pushes water and small solutes out of the blood across the filtration membrane into Bowman's capsule. This pressure-driven process is what initiates urine formation.
Why Other Options are Incorrect:
- A. The ionic electrochemical gradient — Electrochemical gradients drive ion movement across membranes in processes like active transport and diffusion, but they are not the chief force driving bulk filtration across the glomerular membrane.
- C. Protein-regulated diffusion — Filtration across the glomerular membrane is a pressure-driven process, not regulated by transport proteins. Large proteins are actually excluded from filtration.
- D. The size of the pores in the basement membrane — While pore size determines what can be filtered (selectivity), it is not the driving force behind filtration. The hydrostatic pressure is the force that drives fluid through those pores.
The glomerular capsular space contains _______.
- Filtrate
- Plasma
- Urine
- Blood
Explanation
Explanation:
Correct Answer: (A) Filtrate
The glomerular capsular space (the space within Bowman's capsule between the visceral and parietal layers) contains filtrate — the fluid that has been filtered from the blood through the glomerular filtration membrane. This filtrate is essentially plasma minus the large proteins and blood cells, and it will be further processed as it moves through the renal tubules to eventually become urine.
Why Other Options are Incorrect:
- B. Plasma — Plasma remains within the glomerular capillaries; only the filtered portion (minus large proteins) crosses into the capsular space as filtrate.
- C. Urine — Urine is the final product after tubular processing of the filtrate; it is not present in the glomerular capsular space, which is the very beginning of the nephron.
- D. Blood — Blood is contained within the glomerular capillaries and does not enter the capsular space; only the filtered fluid crosses the filtration membrane.
Which of the following statements best describes the difference between the intrinsic and extrinsic controls of the kidney?
- Extrinsic controls will reduce blood plasma volume while intrinsic controls will increase blood plasma volumes
- Extrinsic controls have the greatest effect on systemic blood pressure while intrinsic controls have a greater effect on GFR
- Intrinsic controls raise blood pressure while extrinsic controls lower blood pressure
- Extrinsic and intrinsic controls work in nearly opposite ways
Explanation
Explanation:
Correct Answer: (B) Extrinsic controls have the greatest effect on systemic blood pressure while intrinsic controls have a greater effect on GFR
Intrinsic (autoregulatory) controls — such as the myogenic mechanism and tubuloglomerular feedback — act locally within the kidney to maintain a stable GFR despite changes in blood pressure. Extrinsic controls — such as the sympathetic nervous system and the RAAS — operate systemically and have their greatest impact on systemic blood pressure and overall fluid balance rather than directly on GFR regulation.
Why Other Options are Incorrect:
- A. Extrinsic controls reduce blood plasma volume while intrinsic controls increase it — Both control systems ultimately work to maintain homeostasis; they do not work in opposing directions regarding plasma volume in this manner.
- C. Intrinsic controls raise blood pressure while extrinsic controls lower blood pressure — This is incorrect; extrinsic controls such as the RAAS and sympathetic stimulation are primarily responsible for raising blood pressure, not lowering it.
- D. Extrinsic and intrinsic controls work in nearly opposite ways — While they operate through different mechanisms, they are not opposing systems; both ultimately serve to maintain homeostasis of blood pressure and kidney function.
Which of the following hormones acting on the distal convoluted tubule is most responsible for retaining sodium ions in the blood?
- Parathyroid hormone
- Aldosterone
- Atrial natriuretic peptide
- Antidiuretic hormone
Explanation
Explanation:
Correct Answer: (B) Aldosterone
Aldosterone is the primary hormone responsible for sodium retention in the blood. It acts on the principal cells of the distal convoluted tubule and collecting duct to increase the number of sodium channels and Na⁺/K⁺-ATPase pumps in the cell membranes, promoting sodium reabsorption from the filtrate back into the bloodstream. Water follows the reabsorbed sodium by osmosis, increasing blood volume and pressure.
Why Other Options are Incorrect:
- A. Parathyroid hormone — PTH acts on the DCT to increase calcium reabsorption and decrease phosphate reabsorption; it is not primarily responsible for sodium retention.
- C. Atrial natriuretic peptide — ANP actually promotes sodium excretion (natriuresis) by inhibiting sodium reabsorption in the collecting duct, having the opposite effect of aldosterone.
- D. Antidiuretic hormone — ADH primarily increases water reabsorption by inserting aquaporins in the collecting duct; while it indirectly affects sodium concentration, it is not the primary hormone responsible for sodium retention.
If the glomerular mesangial cells contract, reducing the overall surface area of the glomerulus, which of the following is NOT likely to occur?
- Systemic blood pressure will be lowered
- Glomerular filtration rate will decrease
- Net filtration rate will decrease
- Urine output will decrease
Explanation
Explanation:
Correct Answer: (A) Systemic blood pressure will be lowered
When mesangial cells contract, they reduce the surface area available for filtration, which decreases GFR, net filtration, and urine output. However, reduced filtration and urine output would actually tend to retain more fluid in the body, which would raise or maintain systemic blood pressure, not lower it. Therefore, systemic blood pressure being lowered is NOT an expected outcome.
Why Other Options are Incorrect (i.e., these WOULD likely occur):
- B. Glomerular filtration rate will decrease — TRUE; with reduced surface area available for filtration, less plasma is filtered per unit time.
- C. Net filtration rate will decrease — TRUE; less filtration surface area directly reduces the net amount of filtrate produced.
- D. Urine output will decrease — TRUE; less filtrate formation leads to less urine production and decreased urine output.
Which of the following is the best explanation for why the cells of the proximal convoluted tubule (PCT) contain so many mitochondria?
- Contraction of the PCT moves filtrate through the tubule
- Cells of the PCT go through a great deal of mitosis
- This provides the energy needed to fight kidney infection
- A great deal of active transport takes place in the PCT
Explanation
Explanation:
Correct Answer: (D) A great deal of active transport takes place in the PCT
The PCT is the site of the most extensive reabsorption in the nephron, reabsorbing approximately 65% of filtered water, sodium, glucose, amino acids, and other solutes. Much of this reabsorption involves active transport, which requires ATP as an energy source. The large number of mitochondria in PCT cells reflects the high energy demand needed to power these numerous active transport processes.
Why Other Options are Incorrect:
- A. Contraction of the PCT moves filtrate through the tubule — The PCT does not contract; it is not a muscular structure. Filtrate movement is driven by hydrostatic pressure gradients, not tubular contraction.
- B. Cells of the PCT go through a great deal of mitosis — While PCT cells do have some regenerative capacity, frequent mitosis is not the reason for the high mitochondrial density.
- C. This provides the energy needed to fight kidney infection — Mitochondria in PCT cells are not specifically for immune defense; their presence reflects the metabolic demands of active reabsorption, not infection fighting.
The macula densa cells respond to _______.
- Changes in NaCl concentration of the filtrate
- Antidiuretic hormone
- Aldosterone
- Changes in pressure in the tubule
Explanation
Explanation:
Correct Answer: (A) Changes in NaCl concentration of the filtrate
The macula densa cells are specialized chemoreceptors located in the distal convoluted tubule that detect changes in the sodium chloride (NaCl) concentration of the filtrate passing through the tubule. When NaCl concentration falls, the macula densa signals the granular cells to release renin, initiating the RAAS cascade to restore blood pressure and filtration rate.
Why Other Options are Incorrect:
- B. Antidiuretic hormone — ADH acts on the collecting duct to increase water permeability, not on the macula densa cells.
- C. Aldosterone — Aldosterone acts on the principal cells of the collecting duct to promote sodium reabsorption, not on the macula densa cells.
- D. Changes in pressure in the tubule — Tubular pressure is monitored by the granular cells of the juxtaglomerular apparatus, not specifically by the macula densa cells.
The presence of protein in the urine indicates which of the following?
- Damage to the filtration membrane
- High levels of transcription and translation by the body's tissues
- Damage to the renal tubules
- Too much protein in the diet
Explanation
Explanation:
Correct Answer: (A) Damage to the filtration membrane
Protein molecules, particularly albumin, are normally too large to pass through the intact glomerular filtration membrane. The presence of significant protein in the urine (proteinuria) indicates that the filtration membrane has been damaged, allowing proteins to leak through into the filtrate. This is a hallmark sign of glomerular diseases such as glomerulonephritis and nephrotic syndrome.
Why Other Options are Incorrect:
- B. High levels of transcription and translation by the body's tissues — Protein synthesis activity in body tissues does not directly cause protein to appear in urine; it is the integrity of the filtration membrane that determines protein loss.
- C. Damage to the renal tubules — Tubular damage would affect reabsorption and secretion of small molecules, not typically result in significant proteinuria, as protein filtration is primarily controlled at the glomerular level.
- D. Too much protein in the diet — Dietary protein intake does not directly cause proteinuria; the kidneys efficiently handle normal variations in dietary protein without allowing protein into the urine.
Which of the choices below is NOT a method by which the cells of the renal tubules can raise blood pH?
- By secreting hydrogen ions into the filtrate
- By producing new bicarbonate ions
- By reabsorbing filtered bicarbonate ions
- By secreting sodium ions
Explanation
Explanation:
Correct Answer: (D) By secreting sodium ions
Secreting sodium ions into the filtrate has no direct effect on blood pH. Sodium regulation is primarily related to blood pressure and volume control, not acid-base balance. The renal tubules raise blood pH (make the blood more alkaline) through three key mechanisms: secreting H⁺ ions into the filtrate, producing new bicarbonate ions, and reabsorbing filtered bicarbonate ions — none of which involve sodium secretion.
Why Other Options are Incorrect (i.e., these ARE methods to raise blood pH):
- A. By secreting hydrogen ions into the filtrate — TRUE; removing H⁺ from the blood and excreting it in urine directly raises blood pH.
- B. By producing new bicarbonate ions — TRUE; tubule cells can generate new HCO₃⁻ ions that are added to the blood, increasing its buffering capacity and raising pH.
- C. By reabsorbing filtered bicarbonate ions — TRUE; reclaiming HCO₃⁻ from the filtrate back into the blood helps maintain and raise blood pH by restoring the bicarbonate buffer system.
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