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Free STEP1 Exam Braindumps (page: 63)

Page 62 of 213
PDF with 845 Questions

A 68-year-old woman presents with sleep disturbances and memory loss. After careful analysis, she is diagnosed with early stages of Alzheimer's disease. Her pharmacological treatment plan includes acetylcholine esterase inhibitors. One week after starting treatment, the woman's daughter calls in, reporting that her mom has developed new symptoms that might be related to her new medicine. Which of the following is a likely side effect of the drug?

  1. dry mouth
  2. forgetting to urinate
  3. muscle weakness
  4. nausea and diarrhea
  5. vertigo

Answer(s): D

Explanation:

Increasing the lifetime of acetylcholine by inhibiting its enzymatic breakdown might help existing brain cells to work better. Studies found that Alzheimer patients at early stages might benefit from cholinergic therapy by small improvements in cognitive abilities and a delay in the progression of the disease. However, the side effects of acetylcholine therapy may outweigh the benefits of it. The increased concentration of acetylcholine at postsynaptic nerve endings of the parasympathetic nervous system can result in excessive stimulation of peripheral organ muscarinic and nicotinic receptors. Increased GI motility may occur resulting in nausea and diarrhea. For the same reason, increased salivation, not decreased as in choice A, and increased micturition, and not decreased as in choice B, are expected. Less common side effects include muscle cramps, not muscle weakness as in choice C, due to overstimulation of the cholinergic neuromuscular junction. Acetylcholine overdosing for an extensive time might eventually lead to muscle weakness due to desensitization of postsynaptic acetylcholine receptors, but this is not the best choice in this case. Vertigo (choice E) is the sensation that the room is spinning. Although neurological problems can always lead to kinetoses, there is no direct connection between acetylcholine esterase inhibitors and vertigo.



A 14-year-old female presenting with polyuria is subsequently diagnosed with Type I diabetes mellitus. The polyuria results from an osmotic diuresis that involves primarily which part of the renal tubule?

  1. collecting duct
  2. glomerulus
  3. juxtaglomerular apparatus
  4. proximal tubule
  5. thick ascending limb of the loop of Henle

Answer(s): D

Explanation:

The proximal tubule reabsorbs the majority (about two-thirds) of filtered salt and water. Both the luminal salt concentration and the luminal osmolality remain constant (and equal to plasma values) along the entire length of the proximal tubule. Water and salt are reabsorbed proportionally because the water is dependent on and coupled with the active reabsorption of Na+. The water permeability of the proximal tubule is high, and therefore a significant transepithelial osmotic gradient is not possible. Sodium is actively transported, mainly by basolateral sodium pumps, into the lateral intercellular spaces; water follows. Increased glucose filtration in diabetes will osmotically prevent water reabsorption at this site. The collecting duct (choice A) reabsorbs only a small fraction of filtered Na+ and has a variable water permeability (dependent on ADH levels). The glomerulus (choice B) is where solutes are filtered from the plasma, no reabsorption of salt and water occurs here. The juxtaglomerular apparatus (choice C) produces renin. The thick ascending limb of the loop of Henle (choice E) actively transports and from lumen to the peritubular space using a cotransporter, but is water impermeable so osmotic diuresis will not be produced here.



A person has an elevated plasma osmolality and reduced plasma ADH level and excretes a large volume of osmotically dilute urine. The urine contains no glucose. What is the most likely explanation for this situation?

  1. congestive heart failure
  2. nephrogenic diabetes insipidus
  3. neurogenic diabetes insipidus
  4. primary polydipsia
  5. uncontrolled diabetes mellitus

Answer(s): C

Explanation:

Normally, an elevated plasma osmolarity will stimulate increased ADH secretion and cause increased renal water reabsorption, which should lower the elevated plasma osmolarity. Since in this case ADH is reduced in the face of elevated osmolarity and the kidney is not reabsorbing water, it is clear that neurogenic diabetes insipidus is present (choice C). Choice A is incorrect because congestive heart failure will trigger water retention via the reduced cardiac output and lower arterial pressure, which stimulates ADH release via arterial baroreceptors. Choice B is incorrect because nephrogenic diabetes insipidus results from renal insensitivity to normal, or elevated circulating ADH levels. Choice D is incorrect because primary polydipsia is associated with reduced plasma osmolarity which will suppress ADH release. Choice E is incorrect because diabetes mellitus will be associated with elevated plasma and urine glucose levels.



With respect to below figure, which of the following will decrease the GFR?

  1. decreased hydrostatic pressure in V
  2. decreased plasma protein concentration in W
  3. dilation of X
  4. dilation of Z
  5. increased aldosterone secretion by Y

Answer(s): D

Explanation:

These choices revolve around the Starling forces that directly regulate glomerular filtration. Choice D is correct and choice C is incorrect because glomerular capillary pressure is regulated by the ratio of upstream (afferent arteriole) and downstream (efferent arteriole) resistance to flow. Dilation of the afferent arteriole (choice C) will increase glomerular capillary pressure and increase filtration, whereas dilation of the efferent arteriole (choice D) will decrease the pressure and thus decrease filtration. Choice A is incorrect because Bowman's space pressure normally acts to oppose filtration, hence a decreased pressure will increase filtration. Choice B is incorrect because the osmotic pressure of the plasma proteins opposes filtration, so a decreased plasma protein concentration will predictably increase filtration. Choice E is incorrect, first of all because the juxtaglomerular apparatus does not secrete aldosterone, but instead secretes renin, which ultimately can trigger aldosterone secretion from the adrenal cortex via angiotensin II.
Secondly, aldosterone is likely to trigger salt and water retention by an action on the distal nephron of the kidney, which is likely to alter the Starling forces in favor of increased glomerular filtration.






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